Why the kookaburra’s iconic laugh is at risk of being silenced

Diana Kuchinke, Federation University Australia

Once, while teaching a class of environmental science students in China’s Hebei University of Science and Technology, I asked who knew what a laughing kookaburra was. There were many blank faces. Then I tilted my head, much like a kookaburra does, and opened my mouth: “kok-kak-KAK-KAK-KAK-KOK-KAK-KOK-kook-kook-kok, kok, kok”. I became the “bushman’s alarm clock”.

Students burst out laughing. Hands waved in the air. They knew. They all knew. The call of the kookaburra is known worldwide.

Why do kookaburras “laugh”? It’s a declaration of territory. “I am here. This is my space.”

How long has it been part of the Australian landscape? Indigenous Kamilaroi/Gamilaraay and Wiradjuri people named the “guuguubarra”, so for at least 65,000 years.

Genetic analysis suggests its ancestors can be traced back roughly 16.3 million years. So we can be sure kookaburras have been laughing for a very, very long time.

It is shocking, then, that the laughing kookaburra is now in trouble. A combination of human-driven factors – climate change, bushfires and land clearing – is rapidly driving down numbers of this iconic kingfisher species across its range along Australia’s east coast.

Why are kookaburra numbers falling?

In 2003, the New Atlas of Australian Birds listed the laughing kookaburra as abundant. By 2015, The State of Australia’s Birds report noted them as being in major decline.

What changed? Recent research shows worsening fires are adding to the woes of kookaburras, on top of land clearing, removal of old trees with nesting hollows, state permits to control local numbers and being regarded as an exotic species in Western Australia and Tasmania, where they were introduced more than a century ago.

The tree hollows kookaburras need to breed can take a hundred years to develop. Every forest patch felled means hollows are lost.

Over the past 200 years, nearly 50% of our forest cover has been felled. Urban development all along Australia’s east coast has continued.

Fire is a growing threat

Increasing fire frequency and severity due to climate change are having damaging impacts on kookaburras across south-eastern Australia. Megafires – those that burn more than 10,000 hectares – used to occur about once a decade. Now they are happening more often.

The 2019-2020 “Black Summer” fires were not confined to one state or season. From September 2019 through to March 2020 they burnt more than ten million hectares of native vegetation. The impacts on wildlife were huge.

In the years after fire, the dense regrowth of vegetation gives many birds a flush of abundant resources for food, nesting, cues for breeding and protection from predators.

However, dense new ground growth could hinder the kookaburra’s hunting by making it harder to spot prey. This species sits high in a tree from where it pounces on its prey, which is mostly taken on the ground.

Research has also shown dense post-fire vegetation has less prey, such as basking lizards, a vital part of the kookaburra’s diet.

Research shows laughing kookaburras leave areas of dense post-fire growth. They prefer areas that haven’t burnt for decades.

Kookaburras also compete for prey with other birds, such as the currawong. A currawong forages both on the ground and in the canopy. In denser vegetation, this gives it a competitive advantage over the kookaburra.

If trees with hollows are burnt down, kookaburras also cannot nest. Kookaburras forced to move to new unburnt or uncleared areas must compete for hollows with other highly territorial kookaburras and species such as parrots, owls and possums.

State policies aren’t helping

The Victorian government has issued permits to remove kookaburras from their territories in certain areas. These included three “Authorities to Control Wildlife” by lethal means in 2022 and another in 2023.

The government website says these permits can be issued when wildlife causes damage to property, poses a risk to human health and safety, or is harmful for biodiversity. It is hard to imagine which of these categories justifies permits to kill kookaburras in their native habitat.

The maximum number for lethal control across 2022 was four, and three in 2023. However, kookaburras are highly social birds. They live in family groups of about a dozen individuals with a dominant pair, juvenile helpers and young. If the dominant pair has been dealt with “by lethal means”, it’s devastating for the group.

Two Australian states, Tasmania and Western Australia, treat the laughing kookaburra as an introduced species. In Tasmania (but not WA), the species is unprotected because of its status as an exotic species.

Anecdotal evidence suggests the “first pair” to breed successfully was taken to Tasmania around 1906. But this assumes kookaburras, which are found on other Bass Strait islands, were not already there and could not fly across Bass Strait.

In Tasmania, kookaburras are much maligned and it’s legal to kill them – despite this being the one state where the species isn’t in trouble. One concern is that, as a carnivorous bird, its impact on small reptiles and birds is immense. But other birds, such as the two species of currawong on the island, hunt the same prey as kookaburras.

We can no longer take common species for granted

As climate change results in more bushfires and we continue to clear-fell old habitat trees, the fate of the laughing kookaburra – our icon of the ages – could be sealed. That once-ubiquitous call will be heard no more.

While considerable resources necessarily go to threatened species programs, it is imperative, too, to give more resources and attention to species we have long thought of as common. If species such as kookaburras and koalas are disappearing, then the threatened species have no hope.

Diana Kuchinke, Lecturer in Ecology, Federation University Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Monumental folly and needless greed: how nature is suffering the consequences of climate change

John Woinarski, Charles Darwin University

Set aside the apple and the snake. Set aside the unforgiving God. The loss of Eden is a story about the consequences of monumental folly and needless greed. Having soiled paradise, we live now in a harsher, bleaker world.

In The End of Eden: Wild Nature in the Age of Climate Breakdown, the South African author and naturalist Adam Welz shows we are repeating those errors, sowing and reaping our despoilation. His book is a thoughtful, perceptive, empathetic and sorrowful account of the consequences of our increasing subversion of the natural world that gives us life.

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Review: The End of Eden: Wild Nature in the Age of Climate Breakdown – Adam Welz (Bloomsbury Sigma)

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By now, we are all aware of the devastating losses brought by increasingly frequent environmental catastrophes: the Black Summer bushfires, the floods, the coral bleaching, the droughts, the mass fish kills, the retreat of glaciers, the loss of polar ice, the days of unbearable heat.

Most people recognise that, as the creators of climate change, we are the responsible agents; we have put ourselves on a pathway that is rushing us towards destruction. Many of us have been directly affected; all of us will be indirectly affected.

In End of Eden, Welz describes some of the myriad losses of nature caused by such disasters. One of his examples is the impact of Hurricane Maria on the Puerto Rican parrots known as Iguacas. Following a long history of clearing of its habitat, its remaining wild population became restricted to a single national park in highland rainforest. By 2017, following decades of care by conservation agencies, this remnant population was at last seemingly secure, and the population had built to about 650 birds.

In vivid prose, Wenz describes what then happened when the hurricane tore through and destroyed this forest. Through radio-tracking, scientists were able to establish that maybe only one bird survived the onslaught. But after a few days lost in the devastated landscape, that single bird succumbed too.

In this case, happily, not all was lost for the Iguacas. Although the entire wild population was wiped out, some individuals in a captive breeding facility survived, providing a tenuous thread for the ongoing existence of the species.

It is a story with many lessons, but preparedness for inevitable disaster is an important message.

Subtle entangling impacts

End of Eden does much more than count the environmental toll of individual catastrophes. The effects of climate change are more subtle, more pervasive. Much of its effect is nuanced and gradational, and hence less obvious but more insidious.

Welz’s approach is to paint intricate portraits of plant and animal species, and of places. He gives us insights into how flora and fauna are woven into their ecological setting, then describes how that weave is unravelling.

Some of these accounts are heartbreaking. Millions of years of finely tuned evolution has perfectly adapted the biology of species to their environments. These adaptations are being rendered fragile and increasingly incapable of dealing with the rapid and unremitting changes we have wrought upon the world.

The cheetah is one such case. Exquisitely designed for speed, and hence so successful at hunting in the open plains, its habitat is being crowded out by increasing tree cover, a consequence of rising concentrations of greenhouse gases.

The cheetah’s specialised adaptation is now a failing, and the species is rapidly heading for extinction.

There are many comparable examples. Welz gives accounts of decline and loss of plants and animals, of the gathering emptiness. In some cases, we can decipher the cause, as scientists have – painstakingly, lovingly – learned to see the world from the perspective of a plant or animal, understand its weak points and define the chain of causality.

The Southern Yellow-billed Hornbill of the Kalahari is part of the fabric of that place, but populations are dwindling. Climate change is the root cause, as rising temperatures now often exceed the physiological tolerance of the males, leaving them unable to gather enough food to deliver to their dependent young and brooding females. They starve, and nesting now fails, year after year.

Even more intricately layered is the case of the Red Knot. For one subspecies of this shorebird, the mudflats of northwestern Africa are a key staging point along their migratory route, because within the mud there is a rich resource of small clams. In the 1980s, more than half a million birds congregated there.

But the population has now fallen by at least 80%. The problem lies thousands of kilometres away in the breeding grounds of northern Siberia, where warmer temperatures mean the snow covering melts earlier each year. The Red Knots now arrive too late to coincide their breeding with the pulse of insects that follows the melting snow.

Their young are now malnourished; breeding success has collapsed. Food limitation in infancy has also resulted in shrinkage of their bills. These increasingly shorter-billed birds cannot so readily access the clams hidden below the mud in their non-breeding area. Their bodies, formerly tuned to remarkable migrations, are failing them. Further decline seems inexorable.

There are many other examples of such losses in this book. Each plays out in a different area, at varying pace or magnitude. In each case, a species has its existence cruelled by one or more of the many manifestations of climate change.

These natural history narratives – of species struggling with new regimes of heat or fire or the chemical composition of their environments – illustrate the pervasiveness and multiplicity of climate change’s effects. Individually, they are saddening; collectively, they are devastating.

Change, chaos and causality

Welz writes that “climate change” is too gentle a phrase. He suggests “climate breakdown” is more apt, as it better conveys the likelihood there may be no recovery from this transformation and the multiple, complex and interactive processes that follow from our greenhouse gas emissions.

A characteristic and strength of this book is the counterpointing of its wildlife narratives with explanations of the workings of these causal factors. There are mechanistic descriptions of the processes of fire, thermoregulation, migration, wind, vision and evolution. Through Wenz’s accounts, we see the receding wildlife, but also understand the factors that have subverted their lives.

Much of the collapse of nature – the extinctions, the population crashes of previously abundant species, the losses which we barely perceive – can be attributed to our ongoing destruction of natural habitats, our resource use, the effects of invasive species, and other factors. Climate change is not the only concern.

But climate change compounds these effects. It pervades all natural systems. It has rapidly become the primary driver of much of this decline. And of course the causal factors are, ultimately, due to us.

The End of Eden is a harrowing, necessary book: it shows that we are now witnessing, and causing, the destruction of Eden. We are sentencing our descendants to a less bounteous, less wonderful world. Much of nature has been lost; much more will disappear.

Welz’s concluding chapter does, however, offer a little hope, a frail pathway to recovery. There are no new or startling solutions proposed. Indeed, the final section is cursory. Wenz’s argument is essentially that as we increasingly come to recognise what we are losing – the kinds of losses he documents so well in this book – our society, all of us, will eventually recognise the need to take the actions required to save our future.

We have a limited opportunity to prevent the fall.

John Woinarski, Professor of Conservation Biology, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Great Barrier Reef’s latest bout of bleaching is the fifth in eight summers – the corals now have almost no reprieve

For the fifth time in just the past eight summers – 2016, 2017, 2020, 2022 and now 2024 - huge swathes of the Great Barrier Reef are experiencing extreme heat stress that has triggered yet another episode of mass coral bleaching.

Including two earlier heating episodes – in 1998 (which was at the time the hottest year globally on record) and 2002 – this brings the tally to seven such extreme events in the past 26 years.

The most conspicuous impact of unusually high temperatures on tropical and subtropical reefs is wide-scale coral bleaching and death. Sharp spikes in temperature can destroy coral tissue directly even before bleaching unfolds. Consequently, if temperatures exceed 2°C above the normal summer maximum, heat-sensitive corals die very quickly.

What is coral bleaching?

Bleaching happens when marine heatwaves disrupt the relationship between corals and their “photosynthetic symbionts” – tiny organisms that live inside the corals’ tissues and help power their metabolism.

Severe bleaching is often fatal, whereas corals that are mildly bleached can slowly regain their symbionts and normal colour after the end of summer, and survive.

Before 1998, coral bleaching on the Great Barrier Reef was infrequent and localised. But over the past four decades, bleaching has increased in frequency, severity and sptial scale, as a result of human-induced climate heating.

“Mass coral bleaching” refers to bleaching that is severe and widespread, affecting reefs at a regional scale or even throughout the tropics triggered by rising global sea temperatures.

The Great Barrier Reef consists of more than 3,000 individual coral reefs. It’s the same size as Japan or Italy, and extends for 2,300km along the coast of Queensland. Widespread coral deaths during extreme heatwaves, affecting hundreds of millions of coral colonies, far exceed the damage typically caused by a severe cyclone.

How bad is 2024?

Heat stress this week is reaching record levels on large parts of the Great Barrier Reef.

Climate scientists can measure the accumulation of heat stress throughout the summer by using a metric called “degree heating weeks” (DHW), which factors in both the duration and intensity of extreme heat exposure. This measures how far the temperature is above the threshold that triggers mild bleaching (1°C hotter than the normal summer maximum), and how long it stays above that threshold.

The same DHW exposure can result either from a long, moderate heatwave or from a short, intense peak in temperatures. The 2023–24 summer has been a slow burner on the Great Barrier Reef – sea temperatures have not been as extreme as during previous bleaching events, but they have persisted for longer.

As a general rule of thumb, 2–4 DHW units can trigger the onset of bleaching, and heat-sensitive species of coral begin to die at 6–8 DHW units. So far this summer, according to the US National Oceanographic and Atmospheric Administration, heat stress on the Great Barrier Reef has climbed to 10–12 DHW units on many individual reefs, and has been north and south compared to the central region. Heat stress will likely peak in the next week or two at levels above all previous mass bleaching and mortality events since 1998, before falling as temperatures drop.

Coral bleaching is typically very patchy at the enormous scale of the Great Barrier Reef. In each of the previous events since 1998, 20–55% of individual reefs experienced severe bleaching and coral deaths, whereas 14–48% of reefs were unharmed.

Given the near-record levels of heat stress this summer, we can expect heavy losses of corals to occur on hundreds of individual reefs over the next few months.

What’s the longer-term outlook?

This latest, still-unfolding event was entirely predictable, as ocean temperatures continue to rise due to global heating.

Three of the seven mass bleaching events so far on the Great Barrier Reef coincided with El Niño conditions (1998, 2016 and this summer), and the remaining four did not. Increasingly, climate-driven coral bleaching and death is happening regardless of whether we are in an El Niño or La Niña phase. Average tropical sea surface temperatures are already warmer today under La Niña conditions than they were during El Niño events only three or four decades ago.

The Great Barrier Reef is now a chequerboard of reefs with different recent histories of coral bleaching. Reefs that bleached in 2017 or 2016 have had only five or six years to recover before being hit again this summer – assuming they escaped bleaching during the 2020 and 2022 episodes.

Clearly, the gap between consecutive heat extremes is shrinking – we are vanishingly unlikely to see another 14-year reprieve like 2002 to 2016 again in our lifetimes, until global temperatures stabilise.

Ironically, the corals that are now prevalent on many reefs are young colonies of fast-growing, heat-sensitive species of branching and table-shaped corals – analogous to the rapid recovery of flammable grasses after a forest fire. These species can restore coral cover quickly, but they also make the Great Barrier Reef more vulnerable to future heatwaves.

Attempts to restore depleted coral cover through coral gardening, assisted migration (by harvesting larvae) and assisted evolution (rearing corals in an aquarium) are prohibitively expensive and unworkable at any meaningful scale. In Florida, coral nurseries suffered mass deaths due to record sea temperatures last summer.

The only long-term way to protect corals on the Great Barrier Reef and elsewhere is to rapidly reduce global greenhouse emissions.

Terry Hughes, Distinguished Professor, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Global coral bleaching caused by global warming demands a global response

Britta Schaffelke, Australian Institute of Marine Science; David Wachenfeld, Australian Institute of Marine Science, and Selina Stead, Newcastle University

The fourth global coral bleaching event, announced this week, is an urgent wake-up call to the world.

While the US National Oceanographic and Atmospheric Administration’s announcement is not unexpected, it’s the second global mass bleaching in the past decade. It heralds a new reality in which we can expect more frequent and severe bleaching events as ocean temperature records continue to be broken.

Cycles of decline and recovery are normal for coral reefs, but the windows for recovery are now shorter. Stress events such as marine heatwaves are coming faster, with less warning. These events are also more widespread.

The latest global sea surface temperatures remain above long-term averages.

As the southern hemisphere shifts into winter, the northern hemisphere’s tropical oceans enter summer. Heat will start to accumulate, this year from a higher base. Reefs are more likely to be under greater heat stress earlier than in previous years.

What happened last summer?

Widespread mass bleaching is new for coral reefs. The first global bleaching event was in 1998.

Global mass bleaching events are “called” when significant coral bleaching is confirmed in the Atlantic, Indian and Pacific oceans.

The current event is shaping up to be one of the most severe yet. It began as severe heat stress accumulated in the northern hemisphere summer of 2023. It continued into the southern hemisphere summer of 2023–24.

In the past, summer temperatures on the Great Barrier Reef peaked around February. Now, ocean temperatures are higher for longer. We see maximums above historic values well into April.

On the Great Barrier Reef, large areas were exposed to record-breaking heat stress over its summer (December to March). Prevalent bleaching was observed on three-quarters of surveyed coral reefs in shallow water.

The images below show the reef at North Keppel Island in the southern Great Barrier Reef before bleaching in May 2023 and during bleaching in March 2024. (Click on and drag the slider back and forth to see the difference.)

While it is too early to know the full impact, it is shaping up to be one of the most serious and extensive mass bleaching events recorded on the Great Barrier Reef.

Why are coral reefs so important?

Coral reefs are vital for ocean health. They also provide food, income and coastal protection from storms and floods for an estimated 500 million people. They cover less than 1% of the seafloor but support at least 25% of marine species.

Like the polar regions, coral reefs are especially vulnerable to the effects of climate change. Increasing concentrations of greenhouse gases are heating the oceans.

Can reefs recover from this event?

This current global event is still unfolding. Its full impacts will not be known for some time.

Some coral deaths are immediate. Some colonies recover, while others succumb after the ocean heat subsides. Complex local and species-specific differences are typical for the responses of corals to heat stress and their recovery after an event.

Bleaching occurs when corals under severe stress expel the symbiotic algae living in their tissues, causing them to turn completely white. Though not dead, corals are weakened by bleaching. Those that survive are more susceptible to diseases. Bleaching could also impair their capacity to reproduce.

More than 40 years of data analysed by the Global Coral Reef Monitoring Network show a downward trend in the amount of coral on reefs between 2009 and 2018. This coral loss reflects the cumulative impacts of previous coral bleaching events and local pressures such as pollution, destructive coastal development and overfishing.

After the devastating multiyear bleaching event of 2014–17, some reefs regained some of the lost coral cover during low disturbance periods. Most of the gains were by fast-growing “tabular” corals, which may change reefs’ species composition.

An opportunity to learn more about saving reefs

Long-term monitoring identifies areas of coral reefs that recover naturally after a disturbance, and areas that don’t. This information helps reef managers and scientists know where to focus their efforts to assist reef protection and recovery.

At present, this information is often sparse. Monitoring the world’s reefs is challenging. The total global area of shallow-water coral reefs is estimated at 249,713 square kilometres. Many reefs are in remote locations.

Recent monitoring innovations will improve access to quality data in the medium term.

While devastating, mass coral bleaching events provide a unique opportunity for research to inform actions. In Australia and around the world, scientists are studying which corals are the most tolerant of heat, whether corals are adapting to marine heatwaves, why corals recover differently and how to use this knowledge for interventions that can improve reef resilience.

Science that enables actions that mirror the local conditions – both biophysical and socio-economic – will enable interventions to be more locally relevant.

What can we do?

How fast the world acts to reduce the greenhouse gas emissions driving global warming will determine which reefs, marine species and ecosystem functions and services can be maintained.

A multi-pronged approach for protecting and restoring coral reefs has guided many management strategies, plans and calls to action around the world. These have been largely focused on local and regional actions and solutions. In Australia, there has been significant investment in water-quality management and in research and development of coral reef restoration techniques.

Science plays an important role here. Ideas are cheap but implementation is difficult and expensive. Effective global collaborations can find more cost-effective solutions to improve reef resilience.

Tackling local factors that affect the health of coral reefs remains important, as are innovations to protect and restore coral reefs. But, above all, urgent action to curb the effects of global climate change is vital for the health of our oceans and the people who depend on marine resources.

Britta Schaffelke, Manager International Partnerships and Co-ordinator of the Global Coral Reef Monitoring Network (GCRMN), Australian Institute of Marine Science; David Wachenfeld, Research Program Director – Reef Ecology and Monitoring, Australian Institute of Marine Science, and Selina Stead, CEO, Australian Institute of Marine Science, and Professor of Marine Governance and Environmental Science, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The heat is on: what we know about why ocean temperatures keep smashing records

Over the last year, our oceans have been hotter than any time ever recorded. Our instrumental record covers the last 150 years. But based on proxy observations, we can say our oceans are now hotter than well before the rise of human civilisation, very likely for at least 100,000 years.

This isn’t wholly unexpected. Ocean temperatures have been steadily rising due to human-caused global warming, which in turn means record hottest years have become increasingly common. The last time ocean temperature records were broken was 2016 and before that it was 2015. The last year we experienced a record cold year was way back at the start of the 20th century.

But what is remarkable about the past year is the huge ongoing spike in global ocean temperature which began in April last year. Last year was hotter than the previous record year by a whopping 0.25°C. In contrast the margins of other previous record years were all less than 0.1°C.

Why? Global warming is the main reason. But it doesn’t explain why the heat spike has been so large. Climate drivers such as El Niño likely play a role, as do the random alignment of certain weather events and possibly the reduction in sulfur emissions from shipping. Researchers around the world are trying to understand what’s going on.

How big is the jump in heat?

You can see the surge in heat very clearly in the near-global ocean surface temperature data.

The trend is clear to see. Earlier years (in blue) are typically cooler than later years (in red), reflecting the relentless march of global warming. But even with this trend, there are outliers. In 2023 and 2024, you can see a huge jump above previous years.

These record temperatures have been widespread, with the oceans of the southern hemisphere, northern hemisphere and the tropics all reaching record temperatures.

What’s behind the surge?

We don’t yet have a complete explanation for this record burst of warming. But it’s likely several factors are involved.

First, and most obvious, is global warming. Year on year the ocean is gaining heat through the enhanced greenhouse effect – indeed over 90% of the heat associated with human-caused global warming has gone into the oceans.

The extra heat pouring into the oceans results in a gradual rise in temperature, with the trend possibly accelerating. But this alone doesn’t explain why we have experienced such a big jump in the last year.

Then there are the natural drivers. The El Niño event developing in June last year has certainly played a substantial role.

El Niño and its partner, La Niña, are opposite ends of a natural oscillation, the El Niño Southern Oscillation, which plays out in the tropical Pacific ocean. This cycle moves heat vertically between the ocean’s deeper waters and the surface. When El Niño arrives, warmer water comes up to the surface. During La Niña, the opposite occurs.

You can see the impact of an El Niño on short term temperature spikes clearly, even against a backdrop of strong long-term warming.

But even climate change and El Niño combined aren’t enough to explain it.

Other natural heat-transferring oscillations, such as the Indian Ocean Dipole or the North Atlantic Oscillation, may play a role.

It may also be that our successful efforts to cut aerosol pollution from the dirty fuel shipping relies on has had an unwanted side effect: more warming. With less reflective aerosols in the atmosphere, more of the Sun’s energy can reach the surface.

But there’s probably also a level of random chance. Chaotic weather systems over the ocean can reduce cloud cover, which can let in more solar radiation. Or these weather systems could weaken winds, reducing cooling evaporation.

Why is this important?

To us, a warmer ocean might feel pleasant. But the extra heat manifests underwater as an unprecedented series of major marine heatwaves. The ocean’s organisms are picky about their preferred temperature range. If the heat spikes too much and for too long, they have to move or die.

Marine heatwaves can lead to mass death or mass migration for marine mammals, seabirds, fish and invertebrates. They can cause vital kelp forests and seagrass meadows to die, leaving the animals depending on them without shelter or food. And they can disrupt species important for fisheries and tourism.

This year’s heat stress has caused widespread coral bleaching around the world. Bleaching has been seen on reefs in the Caribbean, Florida, Egypt, and the Great Barrier Reef.

In the cooler waters of Tasmania, extraordinary conservation efforts have been put in place to try and protect endangered fish species such as the red handfish from the heat, while in the Canary Islands, small scale commercial fisheries have popped up for species not normally found there.

Last year, Peru’s anchovy fishery – the country’s largest – was closed for long periods, leading to export losses estimated at A$2.1 billion.

What’s going to happen next?

Given the record temperatures stem from a combination of human-induced climate change and natural sources, it’s very likely ocean temperatures will drop back to more “normal” temperatures. Normal now is, of course, much warmer than in previous decades.

In the next few months, forecasts suggest we have a fair chance of heading into another La Niña.

If this eventuates, we might see slightly cooler temperatures than the new normal, but it’s still too early to know for sure.

One thing is certain though. As we struggle to rein in greenhouse gas emissions, the steady march of global warming will keep adding more heat to the oceans. And another spike in global ocean warming won’t be too far away.

Alex Sen Gupta, Senior Lecturer, School of Biological, Earth and Environmental Sciences, UNSW Sydney; Kathryn Smith, Postdoctoral Research Scientist, Marine Biological Association; Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW Sydney; Neil Holbrook, Professor, University of Tasmania; Thomas Wernberg, Professor, The University of Western Australia, and Zhi Li, Postdoctoral researcher, Centre for Marine Science & Innovation, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Restoring coastal habitat boosts wildlife numbers by 61% – but puzzling failures mean we can still do better

Michael Sievers, Griffith University; Christopher Brown, University of Tasmania, and Rod Connolly, Griffith University

Humans love the coast. But we love it to death, so much so we’ve destroyed valuable coastal habitat – in the case of some types of habitat, most of it has gone.

Pollution, coastal development, climate change and many other human impacts have degraded or destroyed swathes of mangrove forests, saltmarshes, seagrass meadows, macroalgae (seaweed) forests and coral and shellfish reefs. We’ve lost a staggering 85% of shellfish reefs around the world and coral is bleaching globally.

When healthy, these coastal habitats help feed the world by supporting fisheries. They are home to more than 100 species of charismatic marine megafauna, ranging from sharks to dugongs. They sequester carbon, thus helping to slow climate change. The list goes on.

Healthy coastal habitats are the gift that keeps on giving. We need them back, so there’s a lot of enthusiasm for restoring these habitats. For example, we can plant mangroves, build new shellfish reefs and reduce pollution to help seagrass grow back.

But we want to recover more than just the habitats. We want the animals they support too. We need to know if restoration is helping animals.

We analysed restoration projects around the world to assess how animals are benefitting. Compared to degraded sites, restored habitats have much larger and more diverse animal populations. Overall, animal numbers and the types of animals in restored habitats are similar to those in natural habitats.

So restoration works. But outcomes for animals vary from project to project. Not all projects deliver the goods. As a result, resources are wasted and humanity misses out on the huge benefits of healthy coastal habitats.

Animals can respond well to restoration

We collated over 5,000 data points from 160 studies of coastal restoration projects around the world.

Excitingly, animal populations and communities were remarkably similar to those in comparable undisturbed natural sites. For example, restoring seagrass off Adelaide’s coast brought back invertebrates, which are food for many fish species Australians love to catch, such as Australasian snapper. Invertebrate numbers here were comparable to nearby natural seagrass meadows.

Overall, our review found animal populations in restored coastal habitats were 61% larger and 35% more diverse than in unrestored, degraded sites. So restoration produces serious benefits.

Some projects recorded dramatic increases. For instance, after oyster reefs were restored in Pumicestone Passage, Queensland, fish numbers increased by more than ten times. The number of fish species increased almost fourfold.

And animals can occupy newly restored sites surprisingly quickly. Fish and invertebrate numbers in restored seagrass and mangroves can match those in natural sites within a year or two. This happens even though the vegetation is far sparser in restored areas.

Our study shows that efforts to restore coastal habitat certainly can help animals thrive.

Results are not guaranteed

Although restoration generally helped animals, good outcomes are not guaranteed. We found many projects where animal numbers or diversity barely increased. It was not clear why some projects were great for animals and others had lacklustre results.

Some restoration sites could be in places where animals cannot easily find them.

In other cases, actions to restore the habitat may simply not work. Despite our best efforts, we failed to create suitable environments.

It could be that animals are returning to restored habitats, but we’re not capturing them with our monitoring.

We sorely need more consistent restoration outcomes. We may lose community support for restoration if, for example, it doesn’t deliver on promises of improved fisheries.

We are still working out how to restore coastlines effectively. Clearly, more work is needed to improve techniques and the monitoring of animal numbers.

Global alliances and groups are developing standardised frameworks to guide restoration practice and to report on project designs and outcomes. Such strategies and co-ordination promise to deliver more consistent benefits.

New technologies can improve monitoring

Monitoring animals and restoration outcomes in coastal habitats is challenging. These aquatic habitats are structurally complex, often impenetrable and hard to navigate, and can be dangerous.

New technologies, such as artificial intelligence (AI) and environmental DNA (eDNA), allow us to collect more and better data on which animals are present and how they use these habitats. We’re rapidly becoming less reliant on hauling in nets or diving down to count animals.

Artificial intelligence (AI) can be used, for example, to extract information from underwater cameras. We can monitor animals more often, in more places, for less cost.

AI algorithms were recently used to automatically identify, size and count fish in videos taken on restored oyster reefs in Port Phillip Bay, Melbourne. These data were then used to calculate increased fish productivity due to restoration efforts. And what an increase it was – over 6,000 kilograms of fish per hectare per year!

Combining underwater videos with automated data extraction provides a new, reliable and cost-effective method for surveying animals ethically and efficiently.

We still face major barriers to scaling up restoration to even get close to reversing our environmental impact on the coasts. Key concerns include ongoing climate change and policies and laws that hamper restoration efforts. It can be difficult, for example, to get permits to restore habitat, with complex systems involving multiple organisations and arms of government.

Still, our synthesis shows some light at the end of the tunnel. Coastal restoration efforts are having substantial benefits for animals around the world. The evidence supports ambitious restoration targets and action.

Michael Sievers, Research Fellow, Global Wetlands Project, Australia Rivers Institute, Griffith University; Christopher Brown, ARC Future Fellow in Fisheries Science, University of Tasmania, and Rod Connolly, Professor in Marine Science, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate change is causing marine ‘coldwaves’ too, killing wildlife

The effects of ocean warming are profound and well-documented. But sometimes changes in the patterns of winds and ocean currents cause seawater to suddenly cool, instead.

Surface temperatures can plummet rapidly — by 10ºC or more over a day or two. When these conditions persist for several days or weeks, the area experiences a “coldwave”, which is the opposite of more familiar marine heatwaves.

When a “killer coldwave” manifested along South Africa’s southeast coast in March 2021, it killed hundreds of animals across at least 81 species. More worrying still was the fact these deaths included vulnerable manta rays and even specimens of notoriously robust migratory bull sharks. In southern Africa, bull sharks, whale sharks and manta rays have previously washed up dead following such sudden cold events, especially over the past 15 years.

As we report in Nature Climate Change, the conditions that can drive these killer coldwaves have grown increasingly common over the past four decades. Ironically, strengthening winds and currents as a result of climate change can also make these deadly localised coldwaves more likely in places such as the east coasts of South Africa and Australia, potentially putting even highly mobile species such as sharks in harm’s way.

What’s going on?

Certain wind and current conditions can cause the sea surface to cool, rather than warm. This happens when winds and currents force coastal waters to move offshore, which are then replaced from below by cold water from the deep ocean. This process is known as upwelling.

In some places, such as California on the US west coast, upwelling happens regularly along hundreds of kilometres of coastline. But localised upwelling can occur seasonally on a smaller scale, too, often at the edges of bays on the east coasts of continents due to interactions of wind, current and coastline.

Previous research had shown climate change induced changes in global wind and current patterns. So we investigated the potential consequences at particular locations, by analysing long-term wind and temperature data along the south-eastern coast of South Africa and the Australian east coast.

This revealed an increasing trend in the number of annual upwelling events over the past 40 years. We also found an increase in the intensity of such upwelling events and the extent to which temperatures dropped on the first day of each event – in other words, how severe and sudden these cold snaps were.

Mass deaths warrant investigation

During the extreme upwelling event along the southeast coast of South Africa in March 2021, at least 260 animals from 81 species died. These included tropical fish, sharks and rays.

To investigate the ramifications for marine fauna, we took a closer look at bull sharks. We tagged sharks with tracking devices that also record depth and temperature.

Bull sharks are a highly migratory, tropical species that only tend to travel to upwelling regions during the warmer months. With the onset of winter, they migrate back to warm, tropical waters.

Being mobile, they should have been able to avoid the local, cold temperatures. So why were bull sharks among the dead in this extreme upwelling event?

When running and hiding isn’t enough

Bull sharks survive environmental conditions that would kill most other marine life. For example, they’re often found several hundred kilometres up rivers, where other marine life would not venture.

Our shark tracking data from both South Africa and Australia showed bull sharks actively avoid areas of upwelling during their seasonal migrations up and down the coast, even when upwelling isn’t too intense. Some sharks take shelter in warm, shallow bays until the water warms again. Others stick close to the surface where the water is warmest, and swim as fast as they can to get out of the upwelling.

But if marine coldwaves continue to become more sudden and intense, fleeing or hiding may no longer be enough even for these tough beasts. For example, in the event in South Africa that caused the death of manta rays and bull sharks water temperatures dropped from 21°C to 11.8°C in under 24 hours while the overall event lasted seven days.

This sudden, severe drop paired with the long duration made this event particularly deadly. If future events will continue to become more severe, mass deaths of marine life could become a more common sight – especially along the world’s mid-latitude east coasts.

Still learning how climate change will play out

Overall, our oceans are warming. The ranges of tropical and subtropical species are extending towards the poles. But along some major current systems, sudden short-term cooling can make life difficult for these climate migrants, or even kill them. Especially if events like the one in South Africa become more common. Tropical migrants would increasingly be living on the edge of what they are comfortable with in these areas.

Our work emphasises that climate impacts can be unexpected or even counterintuitive. Even the most resilient life forms can be vulnerable to its effects. While we do see an overall warming, changes in weather and current patterns can cause extreme cold events as well.

This really shows the complexity of climate change, as tropical species would expand into higher-latitude areas as overall warming continues, which then places them at risk of exposure to sudden extreme cold events. In this way, species such as bull sharks and whale sharks may very well be running the gauntlet on their seasonal migrations.

The need to limit our impacts on the planet by reducing greenhouse-gas emissions has never been more urgent, nor has been the need for research into what our future might hold.

Nicolas Benjamin Lubitz, Researcher in marine ecology, James Cook University and David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The limits of ice: what a 19th century expedition trapped in sea ice for a year tells us about Antarctica’s future

In 1897, the former whaling ship RV Belgica left Antwerp in Belgium and set sail due south. It was the first voyage of what would become known as the Heroic Age of Antarctic exploration. It did not go to plan.

After a six-month voyage, they begin encountering sea ice. Several times the ship is caught in the ice for a day or two. A crew member falls overboard and is lost to the icy waters. But the crew presses on, making measurements as they go. Expedition leader Adrien de Gerlache records the process:

At noon we made a deep sea sounding, with a long series of temperatures at various depths. We lowered five hundred and sixty metres of wire, and brought up a cup of blue clay. The temperature at the surface was at the freezing point, and at the bottom slightly warmer.

Their discovery of deep warmer water was important. It’s since been named Circumpolar Deep Water. In our time, this water is getting warmer and warmer, as oceans absorb nearly all the extra heat trapped by burning fossil fuels. Antartica’s seemingly impregnable ice is now melting from beneath.

But in 1898, the ice is strong. On March 4, the crew find themselves unable to move. As the southern winter looms, the ice thickens on the surface of the Bellingshausen Sea, to the west of the Antarctic Peninsula. The RV Belgica is trapped.

A winter of permanent night

The crew were about to become the first people to spend a winter south of the Antarctic Circle, enduring months of constant night. The expedition was largely unprepared for the bitter cold and darkness. But the first mate, a 25-year-old Norwegian named Roald Amundsen, felt differently. He had joined the expedition in search of adventure. He was not disappointed. “We must no doubt spend the winter here, and that is fine with me,” he wrote in his journal. Five days in, he writes:

One starts to get familiar with the idea of wintering. The cold has begun sharply. The ice is firm around us and without ridges. This is starting to get interesting.

As time drags on, the crew suffer from scurvy. The expedition leader and his second in command both become so ill they write their wills and retire to bed. Amundsen and the American surgeon Frederick Cook take over leadership.

Of this time, Cook writes in his journal:

we jog along day after day, through the unbroken sameness […] the darkness grows daily a little deeper, and the night soaks hourly a little more colour from our blood

When pale sunlight returns in spring, it’s not enough to free the ship. By January 1899, the crew become desperate. Facing a second winter on the ice, they cut a channel through the sea ice and use explosives to widen it. After a month’s brutal labour, they free the ship and sail for home.

They had been in the ice for just over a year, and had drifted more than 2,000 kilometres as the sea ice moved with the currents.

A little over a decade later, an expedition led by Amundsen would be the first to reach the South Pole.

And the RV Belgica? The ship spent its later years transporting coal, as demand for fossil fuels grew and grew.

What could assail the ice continent?

The scientists and explorers aboard the Belgica did not waste their time. They meticulously recorded their location, the thickness of the sea ice and the weather.

In our time, the data gathered by the scientists and crew of the Belgica is proving invaluable.

Working with the team from the Australian Earth System Simulator, we used data from the Belgica’s crew and satellite imagery to recreate the ship’s path and compare it to what’s happening now.

If the RV Belgica had been in the same location in the Bellingshausen Sea off the Antarctic Peninsula in 2023, rather than 1897, the story would have been very different.

In the intervening 126 years, we set about changing the Earth’s climate in earnest. Fossil fuels gave us vastly more energy. But they came with a sting in the tail – burning them released long-buried carbon dioxide and other gases into the atmosphere, where they magnify the natural greenhouse effect which keeps the Earth from icing over. Almost all of the heat trapped by our activities has gone into the oceans.

In the north, the Arctic sea ice began to disappear from the 1970s onwards, shrinking by about 12% per decade.

Antarctica’s sea ice has held out for longer. A ship like the Belgica could have been stuck in sea ice as late as 2015.

No longer. The heat is on. In the last eight years, Antarctic sea ice has begun to melt in earnest. In the last three years, the melt has accelerated. Now, new research suggests Antarctic sea ice has undergone an “abrupt transition”.

In March 2023, the RV Belgica would have sailed through open waters where pack ice once groaned and cracked. There was almost no sea ice in the Bellinghausen Sea from February to April.

At the beginning of 2024, Australia’s marine research vessel, RV Investigator travelled 12,000km from Hobart down to the Antarctic coastline and back to Fremantle. What was shocking was how easy it was.

When sea ice is at its thickest, even modern vessels can struggle to navigate it. But on this voyage, scientists aboard collected vast amounts of data from dark oceans that should have been covered by thick sea ice.

The years of melting

In the ice continent, climate change is beginning to cause long-feared changes.

The Antarctic Peninsula – the long, trailing tail closest to South America where most tourist ships land – is starting to green. Algae is carpeting more snow, while the two native species of flowering plant, Antarctic pearlwort and Antarctic hair grass, are expanding their range on islands near the peninsula.

In the 19th century, going to Antarctica was a perilous journey, pushing the limits of human endurance. But as the sea ice retreats, it becomes easier and easier for tourist cruise ships to make the journey from ports in Argentina and Chile. Tourist numbers have increased tenfold since the 1990s, rising especially fast in the last two years.

The ice continent has long been defended by the fast, cold water currents in its oceans. But now the heat is getting in – through the water, not the air. The Antarctic Circumpolar Current is speeding up and warmer water is getting into these icy seas. Antarctica’s sea ice is being eaten from below.

That means the so-called Doomsday Glacier is now at risk. The Thwaites Glacier is the size of Great Britain, and holds enough water to singlehandedly raise sea levels 60 centimetres. But the real threat is what’s behind Thwaites. The glacier is a plug, blocking much larger ice rivers from reaching the ocean. If it goes, sea level rise will accelerate.

Antarctica was once a place where humans found their limits. Enduring endless cold and dark and drifting helplessly in the ice, the crew of the Belgica found theirs. As Frederick Cook wrote, the Antarctic night had:

a naked fierceness in the scenes, a boisterous wildness in the storms, a sublimity and silence in the still, cold dayless nights, which were too impressive to be entirely overshadowed by the soul-despairing depression.

A little over a century later, we are finding the ice, too, has limits.

Edward Doddridge, Senior Research Associate in Physical Oceanography, University of Tasmania; Annie Foppert, Research Associate, University of Tasmania, and Stuart Corney, Senior lecturer, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Antarctica’s sea ice hit another low this year – understanding how ocean warming is driving the loss is key

At the end of the southern summer, Antarctica’s sea ice hit its annual minimum. By at least one measure, which tracks the area of ocean that contains at least 15% of sea ice, it was a little above the record low of 2023.

At the time, I was aboard the Italian icebreaker Laura Bassi, ironically surrounded by sea ice about 10km off Cape Hallett and unable to make our way to one of the expedition’s sampling sites.

Even just a decade ago, sea ice reliably rebuilt itself each winter. But something has changed in how the Southern Ocean works and the area covered by sea ice has decreased dramatically.

Our aim was to track the changes happening in the ocean around Antarctica and to make targeted measurements of some of the processes we think are responsible for this loss of sea ice. Most likely, this is a consequence of warming oceans and so we focused on identifying the pathways warmer seawater could find to drive more melting.

The southernmost shelf sea

The annual freeze-thaw cycle of Antarctic sea ice is one of the defining properties of our planet.

It affects the reflectivity of a vast area of the globe, oxygenates the deep ocean, provides habitat across the Southern Ocean food web and plays a role in the resilience of ice shelves.

The voyage was led by a team of scientists who coordinate Italy’s longstanding research in the Southern Ocean.

For decades, they have been maintaining instruments in the Ross Sea region and the data they have been collecting are now proving crucial as we seek to understand the implications of sea-ice changes in terms of physics and biogeochemistry.

The expedition sailed a two-month counter-clockwise loop of the continental shelf in the Ross Sea. Continental shelves are shallower and biologically very productive regions that surround all of Earth’s continents.

Continental shelf seas around Antarctica are special because of the presence of sea ice – but this varies in space and time.

The US National Snow and Ice Data Center has developed a visualisation tool to compare sea-ice conditions during different times.

It shows that by the end of summer, the Ross Sea region holds only a few patches of sea ice. And this year, the patches were even fewer than in the past.

The region is the southernmost open water on the planet and acts as a gateway to seawater flowing in and out under the largest (by area) ice shelf on the planet – the Ross Ice Shelf.

The sea ice we encountered came in a variety of thicknesses and snow cover. We could see that in some places, sea ice was present in densities less than a satellite could recognise, but possibly enough to have an influence on how the upper ocean exchanges heat with the atmosphere above.

The state of sea ice

This reinforced our understanding of the importance of the spatial variability of sea ice. Satellites show that most of the sea-ice coverage, at its minimum, was found in a big patch in East Antarctica, due south of Hobart, and the ice-choked Weddell Sea.

The Weddell Sea and its Filchner-Ronne Ice Shelf are the Ross Sea’s opposite. At the late-summer sea-ice minimum, the Ross Sea is largely free of ice, while the Weddell Sea stays filled with ice.

This was the pack-ice nightmare that trapped Shackleton’s Endurance over a century ago.

At a personal level, the sights during our expedition were a privilege. They took me beyond anything imagined from data and models. Giant icebergs became common place. Penguins, seals, skua and whales all passed by the ship at various times.

In the same way we send people into space, there are substantial benefits to having scientists on location developing their perspectives on the science. However, it is clear that Antarctic ocean data collection systems need to expand when and where they collect information.

The future is robotic

One feature of the voyage was the use of robots. We deployed 11 relatively simple Argo floats that will drift around the region for years, surfacing to send back data on temperature, salinity and in some cases oxygen.

We also sent three robotic ocean gliders on their data-collecting missions independent of the ship. This meant we could capture flow data in the long north-south troughs that are a feature of the region, while the ship was elsewhere.

We retrieved these robot gliders after several weeks, bringing back unique maps of changing ocean temperature and salinity. The data provide evidence of warmer water lying just beneath the edge of the continental shelf, highlighting the fragility of the system.

There is a growing sense that the Ross Sea sector will become more important in the coming decade. With substantial changes upstream in the Amundsen Sea, where glaciers are retreating at an accelerating rate, and the possibility for warmer water finding its way onto the continental shelf, there is the potential that the largest ice shelf on the planet might start to change.

Craig Stevens, Professor in Ocean Physics, University of Auckland, Waipapa Taumata Rau

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Heat from El Niño can warm oceans off West Antarctica – and melt floating ice shelves from below

As snow falls on Antarctica, layers build up and turn to ice. Over time, this compressed snow has become a continent-sized glacier, or ice sheet. It’s enormous – almost double the size of Australia and far larger than the continental United States.

As the weight of ice builds up, the ice sheet begins to move towards the oceans. When it reaches the sea, the ice floats. These floating extensions are known as ice shelves. The largest is over 800 kilometres wide.

When the ocean water has a temperature close to 0°C, these ice shelves can persist for a long time. But when temperatures rise, even a little, the ice melts from below. Antarctic ice shelves are now losing an alarming 150 billion tons of ice per year, adding more water to the ocean and accelerating global sea level rise by 0.6 mm per year. Ice shelves in West Antarctica are particularly prone to melting from the ocean, as many are close to water masses above 0°C.

While the melting trend is clear and concerning, the amount can vary substantially from year-to-year due to the impact of both natural climate fluctuations and human-made climate change. To figure out what is going on and to prepare for the future, we need to tease apart the different drivers – especially El Niño-Southern Oscillation, the world’s largest year-to-year natural climate driver.

Our new research explores how heat brought by El Niño can warm the ocean around West Antarctica and increase melting of the ice shelves from below.

How can El Niño-Southern Oscillation affect Antarctica?

Australians are very familiar with the two phases of this climate driver, El Niño and La Niña, as they tend to bring us hotter, dryer weather and cooler, wetter weather, respectively. But the influence of this cycle is much larger, affecting weather and climate all around the Pacific.

Can it reach through Antarctica’s cold, fast currents of air and water? Yes.

Giant convective thunderstorms in the Pacific’s equatorial regions move east during El Niño and intensify in the West during La Niña. As these storm systems change, they excite ripples in the atmosphere that are able to travel large distances, just as waves can cross oceans. Within two months, these atmospheric waves reach the Antarctic continent, where their energy can affect the coastal atmosphere and ocean circulation. During El Niño, the energy from these waves weakens the easterly winds off West Antarctica (and vice versa for La Niña).

Using satellite data, researchers recently found that West Antarctic ice shelves actually gain height but lose mass during El Niño. That’s because more low-density snow falls at the top of the ice shelves, while at the same time more warm water flows under the ice shelves where it melts compressed high-density ice from underneath.

What we don’t yet know is how this warmer water (above zero) comes up from below. Similarly, we don’t know what happens during La Niña.

Answering these questions with the few observations we have from Antarctica is challenging because this climate driver doesn’t happen in isolation. Storms, tides, large eddy currents and other climate drivers such as the Southern Annual Mode can change the temperatures of the water under ice shelves too, and they can occur at the same time as El Niño.

Finding a needle in the ice stack

So how did we do it? Modelling.

We take a high-resolution global ocean circulation model and added El Niño and La Niña events to the baseline simulation. By doing so, we can examine what these anomalies do to the currents and temperatures around Antarctica.

The energy brought by El Niño’s atmospheric waves to West Antarctica weakens the prevailing easterly winds along the coasts.

Normally, most of the warm water reservoir is located off the continental shelf rather than on the continental shelf. As the winds weaken, more of this warmer water – known as Circumpolar Deep Water – is able to flow onto the continental shelf and near the base of the floating ice shelves.

We call this water mass “warm”, but that’s relative – it’s only 1–2°C above freezing, and the heat only warms the water on the continental shelf by about 0.5°C. But that’s enough to begin melting ice shelves, which are at or below freezing point.

As you’d expect, the longer the warm water stays on the shelf and the hotter it is, the more melting occurs.

During La Niña, the opposite occurs and the ice rebounds. Winds along the coast strengthen, pushing more cold surface water onto the continental shelf and preventing warm water from flowing under the ice shelves.

What does this mean for the near future?

Researchers have found El Niño and La Niña have already become more frequent and more extreme.

If this trend continues, as climate projections suggest, we can expect warming around West Antarctica to get even stronger during El Niño events, accelerating ice shelf melting and speeding up sea level rise.

More frequent and stronger El Niño events could also push us closer to a tipping point in the West Antarctic ice sheet, after which accelerated melting and mass loss could become self-perpetuating. That means the ice wouldn’t melt and reform but begin to steadily melt.

More bad news? Unfortunately, yes. The only way to stop the worst from happening is to get to net zero carbon emissions as quickly as humanly possible.

Maurice Huguenin, Postdoctoral research associate in Physical Oceanography, UNSW Sydney; Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW Sydney, and Paul Spence, Associate professor of oceanography, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

It never rains but it pours: intense rain and flash floods have increased inland in eastern Australia

Milton Speer, University of Technology Sydney and Lance M Leslie, University of Technology Sydney

Before climate change really got going, eastern Australia’s flash floods tended to concentrate on our coastal regions, east of the Great Dividing Range.

But that’s changing. Now we get flash floods much further inland, such as Broken Hill in 2012 and 2022 and Cobar, Bourke and Nyngan in 2022. Flash floods are those beginning between one and six hours after rainfall, while riverine floods take longer to build.

Why? Global warming is amplifying the climate drivers affecting where flash floods occur and how often. All around the world, we’re seeing intense dumps of rain in a short period, triggering flooding – just as we saw in Dubai this week.

Our research shows east coast lows – intense low pressure systems carrying huge volumes of water – are developing further out to sea, both southward and eastward.

This means these systems, which usually bring most of the east coast’s rain during cooler months, are now dumping more rain out at sea. Instead, we’re seeing warm, moist air pushed down from the Coral Sea, leading to thunderstorms and floods much further inland.

This month, a coastal trough along the Queensland and New South Wales coasts and an inland trough resulted in unusually widespread flooding, triggering flooding in Sydney as well as inland.

What’s changing?

On the coasts, extreme flash floods come from short, intense rains on saturated catchments. Think of the devastating floods hitting Lismore in 2022 and Grantham in 2011.

Inland, flash floods occur when intense rain hits small urban catchments, runs off roads and concrete, and flows into low-lying areas.

The April flooding in NSW and Queensland had elements of both. Early this month, the subtropical jet stream changed its course, triggering a cyclonic circulation higher in the atmosphere over inland eastern Australia.

At the same time, a low-pressure trough developed low down in the atmosphere off the coast and another inland, through southern Queensland and NSW, where they encountered warm moist air dragged by northeast winds from as far away as the Coral Sea.

The result was localised extremely heavy rain, which led to the Warragamba Dam spilling and flood plain inundation in western Sydney.

This unusual event has been referred to as a “black nor’easter”, a term coined in 1911. These are characterised by a deepening coastal trough and upper-level low pressure systems further west, over inland eastern Australia. This term, mostly known in the marine fraternity, became less common during the 20th century. But it has returned.

Why? Global warming is changing how the atmosphere circulates. As ocean temperatures keep rising, the pool of warm water in the Coral and Tasman Seas grows. This gives rise to northeasterly airstreams, which funnel thick fronts of warm, moist air down towards inland Queensland and NSW.

These low pressure systems occur higher in the atmosphere, causing unstable conditions suiting the formation of thunderstorms. And because these systems move slowly, heavy rain can fall continuously over the same area for several hours. All up, it’s a perfect recipe for flash flooding.

We saw similar systems producing flash flooding in Sydney’s Nepean and Hawkesbury rivers during November and December last year, as well as in other regions of inland eastern Australia.

Is this new? Yes. Between 1957 and 1990, flash floods struck Sydney 94 times. But during this period, fast cyclonic airflow in the upper atmosphere was not connected to the jet stream. Instead, flash floods occurred when slow-moving upper-level low pressure circulations encountered air masses laden with moisture evaporating off the oceans. However, there wasn’t enough water in the air over the inland to trigger flash flooding.

In every case between 1957 to 1990, flash floods in Sydney were not linked to slower-forming riverine floods on the Nepean-Hawkesbury River system. When these rivers did flood during that period, they came from longer duration, less intense rain falling in the catchments, and largely from east coast lows. Now we’re seeing something new.

Haven’t there always been flash floods?

Flash floods are not new. What is new is where they are occurring. These sudden floods can now form well west of the Great Dividing Range.

Previously, inland floods tended to come after long periods of widespread rain saturated large river catchments. Inland flash floods were not so common and powerful as in recent decades.

In earlier decades, inland riverine floods during extreme rainfall years occurred when the fast-moving jet stream high in the atmosphere was further north. This occurred frequently in the cooler months, with long, broad cloud bands blown by or associated with the jet stream producing widespread rain inland. Known as the “autumn break”, it often primed agricultural land for winter crops.

In recent years, these crucial air currents have begun moving polewards.

Now that it’s moving south, we have increasingly warm air over inland eastern Australia which can hold more moisture and result in heavy falls, even in the cooler months.

What about the famous inland floods which move through Queensland’s Channel Country and fill Kati Thanda/Lake Eyre?

These are slow moving riverine floods, not flash floods. Flash floods are often limited to local regions. By contrast, Channel Country floods stem from heavy monsoonal rains from November to April.

Short, intense rain bursts are going global

The pattern we’re seeing – more flash floods in unusual places – is not just happening in Australia. Inland areas – including deserts – are now more likely to see flash floods.

Dubai this week had a year’s rain (152 mm) in a single day, which triggered flash floods and caused widespread disruption of air travel. Other parts of the United Arab Emirates got even more rain, with up to 250 mm. In Western Australia’s remote southern reaches, the isolated community of Rawlinna recently had 155 mm of rain in a day.

This is precisely what we would expect as the world heats up. Hotter air can hold about 7% more water for every degree of warming, supercharging normal storms. And these floods can be followed by extended periods of almost no rain. The future is shaping up as one of flash floods and flash droughts.

Milton Speer, Visiting Fellow, School of Mathematical and Physical Sciences, University of Technology Sydney and Lance M Leslie, Professor, School of Mathematical And Physical Sciences, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Water theft laws and penalties in the Murray-Darling Basin are a dog’s breakfast. Here’s how we can fix them

Adam James Loch, University of Adelaide; David Adamson, Royal Agricultural University; Mark Giancaspro, University of Adelaide, and Michael Croft, University of Adelaide

Water is one of Australia’s most valuable commodities. Rights to take water from our nation’s largest river system, the Murray-Darling Basin, are worth almost A$100 billion. These rights can be bought and sold or leased, with trade exceeding A$2 billion a year. But water is also being stolen (no-one knows how much) and the thieves usually get away with it.

The federal Labor government came to power promising to crack down on water theft in the Murray-Darling Basin. The Productivity Commission has also expressed concerns about a lack of compliance and enforcement.

The Inspector General of Water Compliance, Troy Grant, has also described existing powers to deter theft as ineffective, and called for urgent action to address inconsistencies in the various state laws that penalise theft from the Murray-Darling Basin. That was almost a year ago.

In our new research, we identified the many relevant laws operating in the basin. We examined these laws and found maximum penalties range wildly. It is a dog’s breakfast. Surely we can do better.

How did we get into this mess?

The mishmash of water theft laws and penalties across the basin is unfortunate but not surprising.

Water in the Murray-Darling Basin is managed under a joint agreement between the federal government, the basin’s four states (Queensland, New South Wales, Victoria and South Australia) and the Australian Capital Territory.

This agreement could be dissolved at any time, should any one state or territory decide to quit.

Murray-Darling Basin compliance is now managed by the Office of the Inspector General of Water Compliance, an independent group of public servants, typically former police officers.

As Inspector General, Grant has been given powers to reduce water theft, uphold compliance with Murray-Darling Basin rules, and restore confidence among those living and working in the basin.

But he was forced to drop 62 cases in February 2023 due to poor state legislative support, inconsistent approaches to water theft, and allowances for some irrigators to balance their accounts in arrears. Basically, Grant stated you had to be a moron to be caught.

Dropped cases lead to questions about water values, continued supply reliability, the extent of environmental harm, and the future security of water rights.

Drought heightens concern about theft

It’s almost 15 years since the most recent review of water theft legislation across state and federal boundaries, which highlighted clear inconsistencies in penalties and approaches to cases.

It’s also nearly ten years since the ABC Four Corners report into large-scale water theft, illustrating the dangers of environmental water harms and wanton disregard by some users for the rights of others.

In more recent droughts, such as the “Tinderbox Drought” of 2017–19, irrigators were more concerned about speculation and hoarding than theft.

But if the basin suffers another serious drought, as predicted by many researchers, it is likely theft will become a top concern for all involved, particularly regulators at state and federal levels.

What’s more, if predictions of climate impacts to water supply are right, available water will dramatically decline in the Murray-Darling Basin, possibly motivating more theft.

We tested this by combining rainfall and runoff data from the Bureau of Meteorology with climate projections from the CSIRO Climate Futures Model and the Garnaut Climate Change Review, to generate a model of future water flows into the southern Murray-Darling Basin up to 2100.

Our research shows we’re on track for a water runoff catastrophe by around 2060, and the eventual collapse of the river’s systems by around 2080. Less rain and higher evaporation rates means less water will runoff the land into streams, rivers and storages. Sobering stuff.

Finding common ground

Our research shows the Inspector General is right: a base comparison of the laws in each state show clear differences, along with the penalties that sit behind them. Calls for greater certainty and consistency are yet to resonate. The positive lessons to be drawn from successful processes are falling on deaf ears.

But we did find some consistent aspects worth noting, which could help us better understand and analyse the legal framework for penalising water theft in the Murray-Darling Basin. This is the “pyramid” approach to assessing cases and applying penalties, using a tiered framework of increasing severity that looks to be applied universally throughout the basin.

The pyramids are based on existing principles already in use for water management around the world.

Most Murray-Darling Basin states already follow this approach. Yet some states do it better than others.

Legal inconsistency also stems from some states being unwilling to “climb to the top” of the pyramid and initiate court proceedings against the most egregious offenders. This leads to lower penalties in most cases.

We also note New South Wales has adopted satellite technology to identify and track water theft. This is a good example for others to follow.

Towards consistent laws

Consistency in compliance and certainty across state jurisdictions will help restore confidence in the water market, and ultimately ensure the Murray-Darling’s water flows are protected from thieves.

We need certain and severe penalties for water theft across the Murray-Darling Basin and Australia as a whole. Such penalties may garner a wider appreciation of the value of the environment.

Addressing water theft issues consistently and with certainty offers opportunities for Australia to again lead the way in effective water governance and compliance reform globally.

But progress has been slow. This is deeply concerning, especially as water flows into the basin will dwindle as the climate changes.

Adam James Loch, Associate Professor, University of Adelaide; David Adamson, Associate professor, Royal Agricultural University; Mark Giancaspro, Senior Lecturer in Law, University of Adelaide, and Michael Croft, Legal Researcher, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The big dry: forests and shrublands are dying in parched Western Australia

Perth has just had its driest six months on record, while Western Australia sweltered through its hottest summer on record. Those records are remarkable in their own right. But these records are having real consequences.

Unlike us, trees and shrubs can’t escape the heat and aridity. While we turn up the air conditioning, they bear the full brunt of the changing climate. Our previous research has shown plants are more vulnerable to heatwaves than we had thought.

Beginning in February 2024, large areas of vegetation started to turn brown and die off. With no real relief in sight, we unfortunately expect this mass plant death event to intensify and expand.

Just like a coral bleaching event, WA’s plants are responding to the cumulative stress of the unusually long, hot and dry summer. And just like bleaching, global heating is likely to cause more regular mass plant deaths. The last time this happened in 2010-11, almost 20% of trees and shrubs in affected areas died.

This is in line with climate change models, which pinpoint south-western Australia as a warming and drying hotspot.

Which trees and shrubs are dying and where?

We have received reports from community members, colleagues, and authorities of dead and dying shrubs and trees spanning approximately 1,000 km from the Zuytdorp Cliffs near Shark Bay down to Albany on the southern coast.

In areas along the west coast where it was hottest, dead or dying patches are larger while further south in the forests, the damage is so far limited to pockets of dead trees and shrinking tree canopies.

At present, the die-off seems to have affected plants on and around shallow soils, including trees near granite outcrops and coastal heath.

While February heatwaves directly killed some plants, it is likely the long, dry period finished the job. Despite some patchy rain last week, no substantial rain is forecast until May. It’s likely more areas will be hit, including our iconic wet forests in the south.

How hot has it been?

Perth once again smashed temperature records this summer with a record thirteen days over 40°C in 2024 to date. Even in April, we had a 37°C day.

This comes off the back of last year’s spring heatwaves, which broke monthly maximum and minimum temperature records in both September and November.

While much of Australia’s east coast had more than enough rain, the west largely missed out.

Rainfall has been below or very much below average over the past year, with the biggest rainfall deficits seen from Shark Bay’s Gascoyne region right down to the southwest corner at Cape Leeuwin.

The summer’s heatwaves came from baking desert air, as high pressure systems directed hot dry easterly winds from Australia’s arid interior over the region, just as we saw during the hot summer of 2021-2022,

Long hot and dry periods are expected to become more common as a result of our warming climate.

Declining rainfall will hit the historically wetter southwest hardest. This pocket of Australia is unique, cut off from the rest of the continent by desert. Here and only here live honey possums and numbats, towering karri and jarrah trees and red flowering gums. But it’s the southwest which has lost most rainfall so far, with annual levels already 20% lower than 50 years ago.

It’s happened before – but this time is worse

Over the summer of 2010-2011, we saw a similar event sweep south-western Australia. It came about when a winter drought gave way to widespread heatwaves over summer. The result: die-off of forests and vegetation throughout the southwest.

On land, the effects extended over a smaller area than we are seeing now.

How bad was it? Pretty bad. Averaging across the region’s affected areas, 19% of trees and shrubs died, while the forests of the south-west lost approximately 16,000 hectares of canopy, about 1.5% of the forest.

When forests die, the effects ripple through the ecosystem. The endangered Carnaby’s black cockatoo population crashed, declining by 60%, while the jarrah forest east of Perth was so hard hit it was categorised at “risk of collapse” by the Intergovernmental Panel on Climate Change.

This time, the summer has been longer and hotter, with impacts on plants more widespread. Climate change is steadily warming the world. Last year was the hottest on record, with temperatures shooting past predictions.

What can we do?

Our trees and shrubs will keep browning off and dying until we get substantial rain. That means there’s no way to tell when our extraordinary range of forest and shrubland species will have the opportunity to recover.

The longer term trend is not good. As with coral bleaching, the situation will worsen until we reverse climate change. Large-scale plant die-offs like this will become more likely.

What we do need are eyes on the ground to track what’s happening across this enormous state. Our ability to understand, model and respond is hampered by a lack of field data.

If you want to help, take photos of dead or dying trees and upload them to the Dead Tree Detectives citizen science project hosted on the Atlas of Living Australia.

Joe Fontaine, Lecturer, Environmental and Conservation Science, Murdoch University; George Matusick, Director, Center for Natural Resources Management on Military Lands, Auburn University; Jatin Kala, Senior Lecturer and ARC DECRA felllow, Murdoch University; Kerryn Hawke, Lecturer in Atmospheric Science, Murdoch University, and Nate Anderson, PhD candidate, The University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Adelaide is losing 75,000 trees a year. Tree-removal laws must be tightened if we want our cities to be liveable and green

Large areas of concrete and asphalt absorb and radiate heat, creating an “urban heat island effect”. It puts cities at risk of overheating as they are several degrees warmer than surrounding areas.

One of the best ways to keep our cool is to maintain leafy streets, parks and backyards. But in some cities, trees are being chopped down faster than local councils can replace them. Some councils are also fast running out of land to plant trees.

Most of the damage happens on private land. Usually it’s a result of large blocks being subdivided or undeveloped land being opened up for more homes.

Cutting down trees for urban development is well within the law. But tree-protection laws are weaker in some parts of Australia than in others. To ensure our cities remain liveable, some laws will have to change.

Why cities need trees

Beyond just providing shade, trees reflect heat into the atmosphere. They also cool the air by releasing water through pores in their leaves, acting like evaporative air conditioners.

Trees provide many other benefits such as removing pollutants, limiting erosion and improving public health.

The influential 3-30-300 rule for green cities, proposed by Dutch researcher Cecil Konijnendijk, states:

• you should be able to easily see three trees from the window of your house or workplace

• cities should have at least 30% overall tree cover

• you should have a green space with trees within 300 metres (or a three-minute walk) of your house or workplace.

Why urban trees need better laws to protect them

How do Australians cities stack up against the 30% canopy goal of the 3-30-300 rule?

Brisbane leads the way, with 44% of the City of Brisbane council area blanketed in trees. Hobart also makes the grade, with analysis of aerial imagery from Google showing a tree canopy of 34%.

Other cities have some work to do to meet the benchmark. Recent aerial image analysis shows Perth sitting at 22% cover.

The NSW Department of Planning reported Sydney’s canopy cover as 21.7% in 2022. The Victorian Department of Transport and Planning reported 15.3% canopy cover across metropolitan Melbourne in 2018.

Green Adelaide reports today that Adelaide’s canopy is a mere 17%. That’s worrying for a city so vulnerable to urban heat.

While it can be tempting to compare canopy results, this needs to be approached with caution. The two main techniques for estimating tree canopy, airborne LiDAR (using laser sensing) and analysis of aerial photographs, can produce different results. Even LiDAR data from the same location but analysed at different resolutions can be quite different.

But what’s concerning is that some cities seem to be losing trees very rapidly. An analysis of aerial photographs by Nearmap shows Adelaide suburbs are fast losing trees. A 2021 Conservation Council report estimates Adelaide is losing about 75,000 trees per year across the city. Most are on private land.

Local councils have been planting several thousand trees each year, but are running out of places to plant them. Requirements for clear space on road verges and around powerlines pose major limitations.

If we want greener cities, we also need to take a critical look at the laws on tree removal.

Our team at the University of Adelaide produced a 2022 report on tree-protection laws across Australia. The state government commissioned us to verify a claim that South Australia’s tree-protection laws were the weakest in the nation. We compared state and local council regulations, and the claim turned out to be true.

What’s wrong with the SA laws?

One consideration is the size thresholds used to define trees as “regulated” or “significant”. Of the 101 metropolitan councils outside SA that we investigated, 78% considered trees with trunk circumferences of more 50cm deserving of legal protection. And 95% applied protection when circumferences exceeded a metre. In South Australia, only trees with twice that trunk size get any legal protection.

Another issue is distance exemptions. In South Australia, large trees that would otherwise be protected may be removed if they are within 10 metres of a house or pool. This rule is regularly used to clear entire residential blocks – after all, nearly all trees on suburban blocks are within 10m of a house or pool.

A majority of the interstate councils had no distance exemptions to speak of.

So what needs to change?

Our findings were among the drivers of a South Australian parliamentary inquiry. An interim report was released last October. It includes sensible, straightforward recommendations to improve the state legislation.

The report suggests reducing the circumference at which trees qualify for protection. It recommends adding crown spread as another criterion. It wisely recommends deleting the distance exemption.

The report also weighs in on fees and fines – the “bottom line” deterrents and punishments for doing the wrong thing. It recommends increasing the fee for legally removing “regulated” trees from $489 to $4,000, for example. However, the value that large trees provide to the community is regularly estimated at hundreds to thousands of dollars per year.

Similarly, a recommendation to introduce a $40,000 fine for illegally removing a “significant” tree pales in comparison to laws interstate. In NSW, illegally removing protected trees can incur fines of over $1 million. To deter big developers, fines must be larger than what they might regard as a reasonable “cost of doing business”.

The report’s recommendation to pay fines and fees into an Urban Forest Fund to grow canopy near areas of tree removal is a good one. Planting trees on the other side of town doesn’t help residents (or biodiversity) when trees are removed locally.

Cities can draw inspiration from each other

Adelaide’s climate is shifting from a temperate Mediterranean climate to a semi-arid one. Semi-arid climates are less able to grow many temperate plant species and tend to have less vegetation overall. To create an extensive and healthy tree canopy for future generations, we need to act fast and think critically about what we’re planting (and protecting).

We hope the South Australian government will follow the inquiry recommendations, so the state’s tree laws are on par with those of other states and cities.

Cities like Melbourne, which are also becoming warmer and drier, can look toward Adelaide as a future climate analogue. Urban planning is often about learning from other cities and adapting their strategies to local contexts.

To cope with the twin challenges of climate change and rapid urban growth, Australian cities need to work together to actively develop greening strategies. If we don’t, our cities will become hot, dry and barren.

Stefan Caddy-Retalic, Ecologist, School of Biological Sciences, University of Adelaide; Kate Delaporte, Senior Lecturer, School of Agriculture, Food and Wine, University of Adelaide, and Kiri Marker, Science Communications Coordinator, Universität Wien

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Roads of destruction: we found vast numbers of illegal ‘ghost roads’ used to crack open pristine rainforest

One of Brazil’s top scientists, Eneas Salati, once said, “The best thing you could do for the Amazon rainforest is to blow up all the roads.” He wasn’t joking. And he had a point.

In an article published today in Nature, my colleagues and I show that illicit, often out-of-control road building is imperilling forests in Indonesia, Malaysia and Papua New Guinea. The roads we’re studying do not appear on legitimate maps. We call them “ghost roads”.

What’s so bad about a road? A road means access. Once roads are bulldozed into rainforests, illegal loggers, miners, poachers and landgrabbers arrive. Once they get access, they can destroy forests, harm native ecosystems and even drive out or kill indigenous peoples. This looting of the natural world robs cash-strapped nations of valuable natural resources. Indonesia, for instance, loses around A$1.5 billion each year solely to timber theft.

All nations have some unmapped or unofficial roads, but the situation is especially bad in biodiversity-rich developing nations, where roads are proliferating at the fastest pace in human history.

Mapping ghost roads

For this study, my PhD student Jayden Engert and I worked with Australian and Indonesian colleagues to recruit and train more than 200 volunteers.

This workforce then spent some 7,000 hours hand-mapping roads, using fine-scale satellite images from Google Earth. Our team of volunteers mapped roads across more than 1.4 million square kilometres of the Asia-Pacific region.

As the results rolled in, we realised we had found something remarkable. For starters, unmapped ghost roads seemed to be nearly everywhere. In fact, when comparing our findings to two leading road databases, OpenStreetMap and the Global Roads Inventory Project, we found ghost roads in these regions to be 3 to 6.6 times longer than all mapped roads put together.

When ghost roads appear, local deforestation soars – usually immediately after the roads are built. We found the density of roads was by far the most important predictor of forest loss, outstripping 38 other variables. No matter how one assesses them, roads are forest killers.

What makes this situation uniquely dangerous for conservation is that the roads are growing fast while remaining hidden and outside government control.

Roads and protected areas

Not even parks and protected areas in the Asia-Pacific are fully safe from illegal roads.

But safeguarding parks does have an effect. In protected areas, we found only one-third as many roads compared with nearby unprotected lands.

The bad news is that when people do build roads inside protected areas, it leads to about the same level of forest destruction compared to roads outside them.

Our findings suggest it is essential to limit roads and associated destruction inside protected areas. If we can find these roads using satellite images, authorities can too. Once an illegal road is found, it can be destroyed or at least mapped and managed as a proper legal road.

Keeping existing protected areas intact is especially urgent, given more than 3,000 protected areas have already been downsized or degraded globally for new roads, mines and local land-use pressures.

Hidden roads and the human footprint

The impact we have on the planet differs from place to place. To gauge how much impact we’re having, researchers use the human footprint index, which brings together data on human activities such as roads and other infrastructure, land-uses, illumination at night from electrified settlements and so on. You can use the index to make heat-maps showing where human impacts are most or least pronounced.

We fed our ghost road discoveries into the index and compared two versions for eastern Borneo, one without ghost road information and one with it. The differences are striking.

When ghost roads are included in mapping the human impact on eastern Borneo, areas with “very high” human disturbance double in size, while the areas of “low” disturbance are halved.

Artificial intelligence

Researchers investigating other biodiversity-rich developing regions such as Amazonia and the Congo Basin have found many illegal unmapped roads in those locales too.

Ghost roads, it seems, are an epidemic. Worse, these roads can be actively encouraged by aggressive infrastructure-expansion schemes — most notably China’s Belt and Road Initiative, now active in more than 150 nations.

For now, mapping ghost roads is very labour-intensive. You might think AI could do this better, but that’s not yet true – human eyes can still outperform image-recognition AI software for mapping roads.

At our current rate of work, visually mapping all roads – legal and illicit – across Earth’s land surface just once would require around 640,000 person-hours (or 73 person-years) to complete.

Given these challenges, our group and other researchers are now testing AI methods, hoping to provide accurate, global-scale mapping of ghost roads in close to real time. Nothing else can keep pace with the contemporary avalanche of proliferating roads.

We urgently need to be able to map the world’s roads accurately and often. Once we have this information, we can make it public so that authorities, NGOs and researchers involved in forest protection can see what’s happening.

Without this vital information, we’re flying blind. Knowing what’s happening in the rainforest is the first step to stopping the destruction.

Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why an intention to conserve an area for only 25 years should not count for Australia’s target of protecting 30% of land

Protected areas have been the cornerstone of efforts to conserve nature for more than a century. Most countries have some form of protected areas, national parks being the best-known examples. A key element of protected areas is that they are dedicated, through legal or other effective means, to long-term conservation of nature.

Australia has taken an innovative and diverse approach to growing its protected area estate. It includes Indigenous Protected Areas and privately protected areas in the form of conservation covenants and land bought by land trusts. As a result, the country’s protected area estate has grown from 7% in the mid-1990s to 22% of the continent today.

Despite this progress, the Australian government has released new draft guidelines for other forms of area-based conservation, with potentially troubling implications. It suggests 25 years of “intention” to deliver biodiversity outcomes is enough for that land to count for the 30% protected area target.

Our newly published research has looked at what types of land use might qualify in line with international guidelines. We found two problems with the proposal to include 25-year plans for biodiversity outcomes.

First, such plans are non-binding, so protection can lapse at any time. Second, they do not satisfy international and Australian principles of long-term protection. Proceeding with this proposal would undermine the goal of long-term conservation in this country.

The new kid in town

In 2010, parties to the Convention on Biological Diversity added a new, slightly unwieldy term, “other effective area-based conservation measures”. These conservation areas (OECMs for short) complement protected areas in achieving global conservation targets. An OECM is a geographically defined area that is not already a protected area, “which is governed and managed in ways that achieve positive and sustained long-term outcomes for the in situ conservation of biodiversity”.

In 2022, the world lifted ambitions for protection and conservation to 30% of land and water areas by 2030 as part of the convention’s Global Biodiversity Framework. There’s been a surge of interest in OECMs to help meet that target.

International guidance on OECMs has been developed only relatively recently. This creates an urgent need for country-specific analysis.

In our peer-reviewed paper in the journal Conservation, we explore policy issues related to OECMs in Australia. We looked at what types of land use might qualify, with a focus on longevity.

What’s the Australian response?

The Australian government has released a draft set of principles to guide OECM development in Australia. The consultation period closes on April 17.

These principles are largely in line with global guidance. However, a couple of significant deviations could compromise Australia’s leadership in area-based conservation.

The most notable deviation relates to the definition of “long-term”. It’s fundamental to whether a site meets the criteria for contributing to global targets. The proposed principles suggest 25 years of “intention” to deliver biodiversity outcomes is enough.

This is a problem for two reasons. First, “intention” does little for biodiversity if the landholder chooses to sell their property a few years after being recognised as an OECM and the new owner has no such conservation interest.

In contrast, conservation covenants are a tool that all states already use to counter against this very scenario. The covenants are attached to the land title and bind future landholders forever. For this reason, these are considered privately protected areas.

Second, a 25-year timeframe is at odds with long-established Australian policy for defining “long-term” for protected areas. A minimum timeframe of 99 years is required if permanent protection is not possible.

The proposal is also inconsistent with the 2023 Nature Repair Act. This law added provision for a 100-year agreement (in addition to its original 25-year agreement) during consultations. This change was based on feedback that 25-year agreements did not equate to long-term.

So where did the 25-year proposal come from? It seems to misinterpret global guidance for privately protected areas. Regardless, adoption of a 25-year “intention” would be a significant backslide for conservation policy in Australia.

So what other areas might count?

Defence land and protected water catchments on public land are often suggested as good candidates in Australia and overseas. Many contain large and significant ecosystem values. The primary use is often compatible with those values.

These areas are also usually permanent fixtures of the landscape, meeting a long-term public need. Thus they would likely qualify as OECMs.

Many local government reserves protect important areas of bushland and manage it for that purpose. Typically, they have not been classified as protected areas. Many are likely to qualify as OECMs.

On private land, it’s a little more challenging. Long-term carbon agreements and biodiversity offset agreements are likely to qualify – despite controversy at times over their primary use.

Land for Wildlife is a successful, high-profile program for engaging landholders with wildlife habitat on their property. Their distinctive blue-diamond-shaped signs adorn over 14,000 properties around the country.

However, these agreements are non-binding. A landholder could remove them at any time. This means they cannot be considered long-term or qualify as an OECM.

Regardless of the assessments above, each site would need to undergo an individual assessment to ensure it meets the criteria.

The importance of longevity

Ultimately, more land managed for conservation is good and all forms of area-based conservation should be encouraged. However, not all forms of area-based conservation qualify for inclusion in global biodiversity targets. Long-term outcomes are fundamental.

Australia has a proud history of innovative protected area policy and approaches. The development of OECM policy in Australia needs to complement and advance that, not erode the standards for long-agreed definitions of long-term.

James Fitzsimons, Adjunct Professor in Environmental Sciences, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate engineering carries serious national security risks − countries facing extreme heat may try it anyway, and the world needs to be prepared

The historic Paris climate agreement started a mantra from developing countries: “1.5 to stay alive.” It refers to the international aim to keep global warming under 1.5 degrees Celsius (2.8 Fahrenheit) compared with preindustrial times. But the world will likely pass that threshold within a decade, and global warming is showing little sign of slowing.

The world is already facing natural disasters of epic proportions as temperatures rise. Heat records are routinely broken. Wildfire seasons are more extreme. Hurricane strength is increasing. Sea level rise is slowly submerging small island nations and coastal areas.

The only known method able to quickly arrest this temperature rise is climate engineering. (It’s sometimes called geoengineering, sunlight reduction methods or solar climate intervention.) This is a set of proposed actions to deliberately alter the climate.

These actions include mimicking the cooling effects of large volcanic eruptions by putting large amounts of reflective particles in the atmosphere, or making low clouds over the ocean brighter. Both strategies would reflect a small amount of sunlight back to space to cool the planet.

There are many unanswered questions, however, about the effects of deliberately altering the climate, and there is no consensus about whether it is even a good idea to find out.

One of the largest concerns for many countries when it comes to climate change is national security. That doesn’t just mean wars. Risks to food, energy and water supplies are national security issues, as is climate-induced migration.

Could climate engineering help reduce the national security risks of climate change, or would it make things worse? Answering that question is not simple, but researchers who study climate change and national security like we do have some idea of the risks ahead.

The massive problem of climate change

To understand what climate engineering might look like in the future, let’s first talk about why a country might want to try it.

Since the industrial revolution, humans have put about 1.74 trillion tons of carbon dioxide into the atmosphere, largely by burning fossil fuels. That carbon dioxide traps heat, warming the planet.

One of the most important things we can do is to stop putting carbon into the atmosphere. But that won’t make the situation better quickly, because carbon stays in the atmosphere for centuries. Reducing emissions will just keep things from getting worse.

Countries could pull carbon dioxide out of the atmosphere and lock it away, a process called carbon dioxide removal. Right now, carbon dioxide removal projects, including growing trees and direct air capture devices, pull about 2 billion tons of carbon dioxide out of the atmosphere per year.

However, humans are currently putting over 37 billion tons of carbon dioxide into the atmosphere annually through fossil fuel use and industry. As long as the amount added is larger than the amount removed, droughts, floods, hurricanes, heat waves and sea level rise, among numerous other consequences of climate change, will keep getting worse.

It may take a long time to get to “net-zero” emissions, the point at which humans aren’t increasing greenhouse gas concentrations in the atmosphere. Climate engineering might help in the interim.

Who might try climate engineering and how?

Various government research arms are already gaming out scenarios, looking at who might decide to carry out climate engineering and how.

Climate engineering is expected to be cheap relative to the cost of ending greenhouse gas emissions. But it would still cost billions of dollars and take years to develop and build a fleet of airplanes to carry megatons of reflective particles into the stratosphere each year. Any billionaire considering such a venture would run out of money quickly, despite what science fiction might suggest.

However, a single country or coalition of countries witnessing the harms of climate change could make a cost and geopolitical calculation and decide to begin climate engineering on its own.

This is the so-called “free driver” problem, meaning that one country of at least medium wealth could unilaterally affect the world’s climate.

For example, countries with increasingly dangerous heat waves may want to cause cooling, or countries that depend on monsoon precipitation may want to restore some dependability that climate change has disrupted. Australia is currently exploring the feasibility of rapidly cooling the Great Barrier Reef to prevent its demise.

Creating risks for neighbors raises conflict alarm

The climate doesn’t respect national borders. So, a climate engineering project in one country is likely to affect temperature and rainfall in neighboring countries. That could be good or bad for crops, water supplies and flood risk. It could also have widespread unintended consequences.

Some studies show that a moderate amount of climate engineering would likely have widespread benefits compared with climate change. But not every country would be affected in the same way.

Once climate engineering is deployed, countries may be more likely to blame climate engineering for extreme events such as hurricanes, floods and droughts, regardless of the evidence.

Climate engineering may spark conflicts among countries, leading to sanctions and demands for compensation. Climate change can leave the poorest regions most vulnerable to harm, and climate engineering should not exacerbate that harm. Some countries would benefit from climate engineering and thus be more resilient to geopolitical strife, and some would be harmed and thus left more vulnerable.

While small experiments have been carried out, nobody has conducted large-scale climate engineering yet. That means that a lot of information about its effects relies on climate models. But while these models are excellent tools for studying the climate system, they’re not good at answering questions about geopolitics and conflict. On top of that, the physical effects of climate engineering depend on who is doing it and what they’re doing.

What’s next?

For now, there are more questions about climate engineering than answers. It’s hard to say whether climate engineering would create more conflict, or if it could defuse international tensions by reducing climate change.

But international decisions on climate engineering are likely coming soon. At the United Nations Environment Assembly in March 2024, African countries called for a moratorium on climate engineering, urging all precaution. Other nations, including the United States, pressed for a formal scientific group to study the risks and benefits before making any decisions.

Climate engineering could be part of an equitable solution to climate change. But it also carries risks. Put simply, climate engineering is a technology that can’t be ignored, but more research is needed so policymakers can make informed decisions.

Ben Kravitz, Assistant Professor of Earth and Atmospheric Sciences, Indiana University and Tyler Felgenhauer, Research Scientist in Civil and Environmental Engineering, Duke University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Flash droughts are becoming more common in Australia. What’s causing them?

Milton Speer, University of Technology Sydney and Lance M Leslie, University of Technology Sydney

Flash droughts strike suddenly and intensify rapidly. Often the affected areas are in drought after just weeks or a couple of months of well-below-average rainfall. They happen worldwide and are becoming more common, including in Australia, due to global warming.

Flash droughts can occur anywhere and at any time of the year. Last year, a flash drought hit the Upper Hunter region of New South Wales, roughly 300 kilometres north-west of Sydney.

These sudden droughts can have devastating economic, social and environmental impacts. The damage is particularly severe for agricultural regions heavily dependent on reliable rain in river catchments. One such region is the Upper Hunter Valley, the subject of our new research.

We identified two climate drivers – the El Niño Southern Oscillation and Indian Ocean Dipole) – that became influential during this drought. In addition, the waning influence of a third climate driver, the Southern Annular Mode), would typically bring rain to the east coast. However, this rain did not reach the Upper Hunter.

Flash droughts are set to get more common as the world heats up. This year, a flash drought developed over western and central Victoria over just two months. While heavy rain this month in Melbourne ended the drought there, it continues in the west.

What makes a flash drought different?

Flash droughts differ from more slowly developing droughts. The latter result from extended drops in rainfall, such as the drought affecting parts of southwest Western Australia due to the much shortened winter wet season last year.

Flash droughts develop when sudden large drops in rainfall coincide with above-average temperatures. They mostly occur in summer and autumn, as was the case for Asia and Europe in 2022. That year saw flash droughts appear across the northern hemisphere, such as the megadrought affecting China’s Yangtze river basin and Spain.

The flash drought devastating the Upper Hunter from May to October 2023 developed despite the region being drought-free just one month earlier. At that stage, almost nowhere in NSW showed any sign of an impending drought.

The flash drought greatly affected agricultural production in the Upper Hunter region, due to the region’s reliance on water from rivers. Low rainfall in river catchments means less water for crops and pasture. It also dries up drinking water supplies.

Flash droughts are characterised by abrupt periods of low rainfall leading to rapid drought onset, particularly when accompanied by above-average temperatures. Higher temperatures increase both the evaporation of water from the soil and transpiration from plants (evapotranspiration). This causes soil moisture to drop rapidly.

The Upper Hunter drought is part of a trend

Flash droughts will be more common in the future. That’s because higher temperatures will more often coincide with dry conditions, as relative humidity falls across many parts of Australia and globally.

Climate change is linked to shorter, heavier bursts of rain followed by longer periods of little rainfall.

In south-east and south-west Australia, flash droughts can also occur in winter.

In May 2023 rainfall over south-east Australia dropped abruptly. The much lower rainfall continued until November in the Upper Hunter. Over this same period, mean maximum temperatures in the region were the highest on record, increasing the loss of moisture through evapotranspiration. The result was a flash drought. While flash droughts occurred in other parts of south-east Australia, we focused on the Upper Hunter as it remained in drought the longest.

What were the climate drivers of this drought?

We used machine-learning techniques to identify the key climate drivers of the drought.

We found the dominant driver of the flash drought was global warming, modulated by the phases of the three major climate drivers in our region, the El Niño Southern Oscillation, Indian Ocean Dipole and the Southern Annular Mode.

From 2020 to 2022, the first two drivers became favourable for rain in the Upper Hunter in late winter through spring, before changing phase to one supporting drought over south-east Australia. Meanwhile, the Southern Annular Mode remained mostly positive, meaning rain-bearing westerly winds and weather fronts had moved to middle and higher latitudes of the southern hemisphere, away from Australia’s south-east coast.

Combined, the impact of global warming with the three climate drivers made rainfall much more variable. The net result was an atmospheric environment highly conducive to a flash drought appearing anywhere in south-east Australia.

Victoria, too, fits the global warming pattern

As for the flash drought that developed in early 2024 over western and central Victoria, including Melbourne, it continues in parts of western Victoria. The flash drought followed very high January rainfall (top 5% of records) dropping rapidly to very low rainfall (bottom 5%) in February and March.

It was the driest February-March period on record for Melbourne and south-west Victoria.

At the beginning of April, a storm front brought heavy rainfall over an 18-hour period to central Victoria, including Melbourne.

The rains ended the flash drought in these areas, but it continues in parts of western Victoria, which missed out on the rain.

The pattern of the 2024 flash drought in Victoria typifies the increasing trend under global warming of long dry periods, interspersed by short, heavy rainfall events.

Milton Speer, Visiting Fellow, School of Mathematical and Physical Sciences, University of Technology Sydney and Lance M Leslie, Professor, School of Mathematical And Physical Sciences, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What if whales took us to court? A move to grant them legal personhood would include the right to sue

In a groundbreaking declaration earlier this month, Indigenous leaders of New Zealand and the Cook Islands signed a treaty, He Whakaputanga Moana, to recognise whales as legal persons.

Aotearoa New Zealand has already granted legal personhood to a river (Te Awa Tupua Whanganui River), land (Te Urewera) and a mountain (Taranaki maunga), but He Whakaputanga Moana differs from these earlier processes. It is based in customary law, or tikanga Māori, rather than Crown law.

The declaration seeks to protect the rights of whales (tohorā) to migrate freely and to use mātauranga Māori alongside science for better protections. It also aims to set up a dedicated fund for whale conservation.

But a core concept of legal personhood is the idea that the “person” (in this case, whales) can sue to protect their rights.

The declaration was signed by King Tuuheitia Pootatau Te Wherowhero VII of the Kiingitanga movement, Lisa Tumahai who chairs the Hinemoana Halo Ocean initiative, and the Cook Islands leader Kaumaiti Nui Travel Tou Ariki.

It recognises traditional Māori and Pasifika ideas about the importance of whales as ancestral beings. King Tuuheitia described it as “a woven cloak of protection for our taonga”, noting the presence of whales “reflects the strength of our own mana”.

While He Whakaputanga Moana is not a pan-Māori declaration, mana is a shared core concept of tikanga Māori, representing authority and power.

What is legal personhood?

Over the past few hundred years, legal personhood has been developed for companies as a way for individual shareholders to avoid liability. This means a company can go to court, rather than its shareholders.

In the past decade, Aotearoa New Zealand has led the way in developing legal personhood for things in nature into a tool used as part of settlements under Te Tiriti o Waitangi/Treaty of Waitangi. It is important to note that these ideas have been recognised and implemented by the Crown in partnership with Māori.

As part of the signing of the Tūhoe settlement in 2014, the former national park Te Urewera was granted legal personhood. In 2017, legal personhood for the Whanganui river was also part of a settlement. And last year, this idea was extended to Mount Taranaki. The Taranaki Maunga Collective Redress Bill passed its first reading in parliament last week.

These natural features are now not owned by people or the Crown, but by themselves.

Legal personhood has been praised in New Zealand and overseas by people interested in using it to protect the environment.

Tikanga key to unlocking legal power

There is currently a shift in the legal system to recognise tikanga as a key source of law alongside statute and common law (the kind of customary law New Zealand inherited from England).

In the recent case of Ellis v R, the Supreme Court recognised and applied ideas about mana. In deciding to overturn the conviction of Peter Ellis posthumously, the court held that Mr Ellis’ mana was affected by the convictions, even after his death.

He Whakaputanga Moana is based on customary concepts like mana rather than being a Crown-drafted piece of law. It is likely it could be recognised by the courts as part of the growing wave of tikanga jurisprudence.

Marine mammals in New Zealand’s territorial waters are protected absolutely by the Marine Mammals Protection Act 1978 (as has recently been highlighted when the Sail GP regatta was held in a marine sanctuary and races were delayed because dolphins were present).

But He Whakaputanga Moana recognises legal personhood above and beyond that legislation.

Whales in court

So what if whales went to court? What if whales sued for plastic pollution in their habitat, the dumping of waste in the oceans or climate change causing warmer waters and depleting their food stocks?

In this case, He Whakaputanga Moana could potentially give a human interest group, perhaps the Kiingitanga, the legal standing to sue on behalf of whales.

In addition to recognising tikanga as a source of law, the Supreme Court has also opened the door to climate change focused litigation, such as the case of Smith v Fonterra.

Here, activist Mike Smith has sued seven major New Zealand polluters for their greenhouse gas emissions. The defendants said the claim could not succeed and applied for a “strike out”, but the Supreme Court has allowed it go to trial.

Among other findings, the court found the litigation should proceed, as it might involve ideas of tikanga and tikanga-based loss that should be tested at trial. This suggests that if the courts were to recognise the validity of He Whakaputanga Moana in customary law, this case might allow those representing whales to run a claim against ocean polluters.

A ruling in favour of whales could have significant ramifications for the health and wellbeing of our oceans, and perhaps the very existence of their species.

Rachael Evans, Lecturer, Kaupeka Ture | Faculty of Law, University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Light pollution affects coastal ecosystems too – this underwater ‘canary’ is warning of the impacts

Kathleen Laura Sterup, Te Herenga Waka — Victoria University of Wellington and Abigail M Smith, University of Otago

In the early 20th century, canaries were used as early warning systems in coal mines to alert miners to rising levels of carbon monoxide.

A small unremarkable fish may fill a similar role in coastal ecosystems around Aotearoa New Zealand.

Triplefins, or kokopara, are common in a range of shallow coastal habitats across the country. They are a diverse group of fishes, with 26 endemic species living on our shores, and they make excellent “canaries” for the coastal marine environment, helping us to understand and possibly address pollution.

Research using triplefins has already shown increased consumption of microplastics by fish living closer to urban areas. Studies have also identified molecular responses to multiple chemical pollutants and described cognitive damage caused by loss of habitat complexity.

Noise pollution from small boats also has negative effects on coastal fish. And now, new research is investigating the surprising impact of light pollution on coastal ecosystems.

We are finding what is called “skyglow” affects triplefin growth patterns, with consequences for their ability to forage.

An underwater ‘canary’

Human activity around coastal waters is intense, about triple the rate of other areas, and it affects ecosystems such as beaches and wetlands.

Coastal urbanisation introduces a range of challenges for near-shore ecosystems, including pollutants, plastics, sound and light.

Light pollution is often recognised for the limitations it imposes on astronomers and stargazers, but a growing body of research has begun to document effects on the health of animals and ecosystems.

Scientists have found coastal fishes in tropical and temperate environments, including the common triplefin, reproduce and grow in a cyclical pattern which follows the monthly lunar cycle.

Patterns in nocturnal illumination (known as artificial light at night, or ALAN) of surface waters have a surprisingly large impact on these fish. The prevalence of light pollution from cities (in this case New Zealand’s capital Wellington) can potentially interfere with their breeding cycles.

Long-term trends in skyglow over the Wellington region have revealed elevated levels of nighttime illumination up to 60 kilometres from the city centre.

Analysis of triplefin samples from nearby waters has identified altered growth patterns, manifesting in different body shapes. The health consequences include decreased swimming and foraging ability and make life harder for fish developing in brighter waters.

Bright city lights

It may not seem that the effects of light on a tiny fish are a big deal, but triplefins are a clear indicator of what could be happening in other fish.

In marine ecosystems, small changes have a way of propagating further up the food chain. In the light pollution example, theory suggests small-scale, relatively short-term fluctuations in small prey species like the common triplefin are likely to appear later as long-term fluctuations in larger species at a greater spatial scale, with genuine implications for pelagic fisheries.

In an instance such as this, the triplefin is indeed acting as a canary for potential changes affecting the entire marine food web.

We know what affects one fish species may not affect others. But equally, we can’t carry out experiments on every species. What the humble triplefin can tell us is that coastal ecosystems are in trouble, not just from water quality and pollution, but from the lights and sounds of our big cities.

Like the miners, we need to pay attention to the animals we use as indicators. The triplefins are asking us to embrace the dark and there are many ways in which our cities can do this.

Communities can choose LED lightbulbs and shaded fixtures for street lights, so they only point down. Sensible use of dimmers and timers will help turn off unnecessary lights. In fact, Aotearoa New Zealand hosts two of the world’s few dark sky reserves, in Aoraki-McKenzie and, more recently, in the Wairarapa, as well as two dark sky sanctuaries (Aotea/Great Barrier Island and Rakiura/Stewart Island).

New Zealand could be on track to become the second dark sky nation in the world (after Niue).

Kathleen Laura Sterup, Postgraduate in Marine Biology, Te Herenga Waka — Victoria University of Wellington and Abigail M Smith, Professor of Marine Science, University of Otago

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What is a sinkhole? A geotechnical engineer explains

Sinkholes are back in the news after a 13-year-old boy fell down a two metre deep hole in a waterlogged football field in Sydney over the weekend. The boy reportedly sank further into the hole every time he tried to push down with his feet, but was later rescued by a police officer who pulled him out by his wrists.

Sinkholes aren’t uncommon. Two opened up in the Sydney suburb of Rockdale in March, one of which reportedly left a commercial building at risk of collapsing. Another large sinkhole opened up in the South Australian city of Mount Gambier last year.

So, what is a sinkhole and why do they happen?

What is a sinkhole?

A sinkhole is basically a hole which appears to suddenly open up in the ground. However, the process that leads to a sinkhole is not so sudden and may have been developing over a long period.

Sinkholes happen when a cavity starts to grow underground. It expands over time, but the soil on the surface is strong enough to hold together and form a “ceiling” over the cavity. This ceiling is essential, otherwise you don’t have a sinkhole; you just have a hole.

At some point the surface layer becomes too thin or too weak and it collapses under its weight (or, in the Sydney case on the weekend, under the weight of a 13-year-old boy).

When the ceiling collapses you end up with a hole that exposes the cavity previously hidden underground.

If the cavity is deep enough underground and surrounded by strong enough rocks, it may grow and never collapse, eventually forming tunnels and cave systems. In some cases, however, these caves may link up with localised sinkholes at the surface.

So what causes the cavity?

Acidic rainwater can degrade underground rock. This can create underground caves which can eventually collapse into sinkholes. Sinkholes of this type need a specific type of geology; you need certain rocks prone to dissolution. It is common in the Middle East and the United States for example.

In Australia, we more commonly see sinkholes emerging due to underground erosion. Here, flowing groundwater carries soil out of the area. The more the cavity opens up underground, the more water gets drawn to it and the higher the chance of a sinkhole. Water flow rate can increase over time, creating a snowball effect heightening the risk of the soil ceiling collapsing.

The sinkhole that appeared in Sydney over the weekend may already have been growing quietly for a while, and could have expanded faster as the weekend’s intense rain soaked into the soil. All it took was someone to walk over the top.

Human factors can play a part. For example, a leaking underground pipe can, over time, worsen underground erosion and may increase risk of a sinkhole developing.

How common are they?

They are not uncommon but it’s not really possible to say how many are in Australia.

The sinkholes you hear about in the media generally attract attention because they are in a city, so the public are more likely to interact with them and the risk to buildings or people may be greater.

But they can happen everywhere. I have seen them while bush walking just outside of Sydney.

How dangerous are they?

Most will not be dangerous as they may be quite small. But until the surface opens, there’s no way of knowing there is a sinkhole underground, and it’s hard to know from the outside what size cavity sits beneath the surface. You might have a small opening you can see from the surface but a very big cavity underneath.

That can make them dangerous or, at the very least, a problem.

Large sinkholes can happen but small ones are much more common. To get to bigger ones, the cavity ceiling needs to be able to sustain itself for a very long period of time, which is unusual.

But they can get very big. There are some very large sinkholes in Mexico that I discuss in my unit on geotechnical engineering. One has a diameter of about 60 metres.

A 30-metre-wide sinkhole opened up in the Japanese city of Fukuoka in 2016.

Another example of an area prone to sinkholes is Florida, as the carbonate rocks in the ground there are more susceptible being dissolved by water.

So in general, sinkholes are not uncommon but they usually don’t get reported unless they are very big or pose a risk to people or property.

My colleagues and I have a grant to study the formation of sinkholes, so we can better understand risk and how to predict where they might happen.

Francois Guillard, Senior Lecturer in Geotechnical Engineering, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Things that go buzz in the night – our global study found there really are more insects out after dark

Mark Wong, The University of Western Australia and Raphael Didham, The University of Western Australia

Have you ever wondered if there are more insects out at night than during the day?

We set out to answer this question by combing through the scientific literature. We searched for meaningful comparisons of insect activity by day and by night. It turns out only about 100 studies have ever attempted the daunting and rigorous fieldwork required – so we compiled them together to work out the answer.

Our global analysis confirms there are indeed more insects out at night than during the day, on average. Almost a third more (31.4%), to be precise. But this also varies extensively, depending on where you are in the world.

High nocturnal activity may come as no surprise to entomologists and nature photographers. Many of us prowl through jungles wearing head torches, or camp next to light traps hoping to encounter these jewels of the night.

But this is the first time anyone has been able to give a definitive answer to this universal childlike question. And now we know for sure, we can make more strident efforts to conserve insects and preserve their vital place in the natural world.

Building a global dataset of sleepless nights

We searched the literature for studies that sampled insect communities systematically across day and night.

We narrowed these down to studies using methods that would not influence the results. For instance, we excluded studies that collected insects by using sweep nets or beating branches, as these methods can capture resting insects along with active ones.

Studies using light traps or coloured pan traps had to be excluded too. That’s because insects are only attracted to these well-lit traps when there’s low light in the surrounding environment, so they don’t work so well during the day.

Instead, we targeted studies that sampled insects during the day and night with traps that specifically caught moving insects. These include pitfall traps (for crawling insects), flight interception traps (for flying insects) and aquatic drift nets (for swimming insects).

We also accepted studies using food baits such as dung, for some beetles or honey (for ants).

One of the most memorable studies we encountered sampled mosquitoes using (unfortunate) human subjects as bait. Another had devised innovative automatic time-sorted pitfall traps to minimise the labour required, as the specimens collected would automatically be delivered into different compartments at different times of the day.

But in most of the studies that we ended up including in our analysis, the data had been collected by entomologists who set up many traps before dawn, returned before sunset to collect the day’s samples and prepare more traps for the night, and finally, returned once more before dawn to retrieve the night’s samples.

To improve their estimates of insect activity, many studies reported data that spanned multiple days and field sites. The sacrifice of sleep in the name of science is a true testament to their dedication.

Eventually, we homed in on 99 studies published between 1959 and 2022. These studies spanned all continents except Antarctica and encompassed a wide range of habitats on both land and water.

What did we find?

We found more mayflies, caddisflies, moths and earwigs at night. On the other hand, there were more thrips, bees, wasps and ants during the day.

Nocturnal activity was more common in wetlands and waterways. In these aquatic areas, there could be twice as many insects active during the night.

In contrast, land-based insects were generally more active during the day, especially in grasslands and savannas. We found the number of insects out and about could triple during the day in these habitats.

This may have something to do with avoiding predators. Fish tend to hunt aquatic insects during the day, whereas nocturnal animals such as bats make life on land more hazardous at night.

We also found insects were more active at night in warmer parts of the globe, where there are higher maximum temperatures. Insects are “ectotherms”, which means they are unable to regulate their body temperature. They are particularly susceptible to extremes in temperature, both hot and cold. This finding underscores the role of climate in regulating insect activity.

Given temperatures peak during the day, higher maximum temperatures may foster increased nocturnal activity as more individuals seek to avoid heat stress by working in the dark.

Findings underscore the threats to nocturnal insects

Insects perform many vital “ecosystem services” such as pollination, nutrient cycling and pest control. Many of these services may be provided at night, when more insects are active.

This means we need to curtail some of our own activities to support theirs. For instance, artificial lighting is detrimental to nocturnal insects.

Our research also points to the threat of global warming. In the hottest regions of the globe such as the tropics, the warming trend may further reduce the activity of nocturnal insects that struggle to cope with heat. To this end, we hope our study motivates day-loving ecologists to embrace night-time ecology.

Insects are among the most diverse and important organisms on our planet. Studying their intricate rhythms represents not just a scientific endeavour, but an imperative for preserving wildlife.

Mark Wong, Forrest Fellow, School of Biological Sciences, The University of Western Australia and Raphael Didham, Professor of Ecology, The University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.