Sydney's disastrous flood wasn't unprecedented: we're about to enter a 50-year period of frequent, major floods

Last month’s flood in the Hawkesbury-Nepean River region of western Sydney peaked at a staggering 12.9 metres, with water engulfing road signs and reaching the tops of many houses.

There hasn’t been a major flood on the Hawkesbury-Nepean for more than 30 years, with the last comparable one occurring in 1990. Long-term Sydneysiders, however, will remember that 12 major floods occurred during the 40 years before 1990. Five of these were larger than last month’s flood.

So what’s going on? The long-term rainfall pattern in the region and corresponding river flow is cyclic in nature. This means 40 to 50 years of dry weather with infrequent small floods are followed by 40 to 50 years of wet weather with frequent major floods.

As river and floodplain residents take stock of the recent damage to their homes and plan necessary repairs, it’s vital they recognise more floods are on the way. Large, frequent floods can be expected to occur again within 10 or 20 years if — as expected — the historical pattern of rainfall and flooding repeats itself.

Living in a bathtub

Many of the 18,000 people who were evacuated live in and around a region known as the “Sackville Bathtub”. As the name suggests, this flat, low-lying section of the floodplain region was spectacularly affected.

The Sackville Bathtub is located between Richmond and Sackville. It’s part of the Cumberland Plain area of Western Sydney and formed very slowly over 100 million years due to plate tectonic processes. The bathtub’s mudstone rock layers are folded into a broad, shallow, basin-shaped depression, which is surrounded by steep terrain.

Downstream of Sackville, the Hawkesbury-Nepean River flows through sandstone gorges and narrows in width. This creates a pinch-point that partially blocks the river channel.

Just as a bath plug sitting half-way over a plughole slows an emptying bath, the Sackville pinch-point causes the bathtub to fill during floods.

Will raising the dam wall work?

The NSW state government is planning to raise the wall of the Warragamba Dam to help mitigate catastrophic floods in the region. But this may not be an effective solution.

Typically, somewhere between 40% and 60% of the floodwater that fills up the Sackville Bathtub comes from unimpeded, non-Warragamba sources. So, when the Hawkesbury-Nepean River floods, the bathtub is already quite full and causing significant problems before Warragamba begins to spill. The Warragamba water then raises the flood level, but often by only a couple of metres.

Raising Warragamba Dam’s wall as a mitigation measure will only control about half the floodwater, and won’t prevent major floods delivered by the Nepean and Grose rivers, which also feed into the region. This represents a small potential benefit for a very large cost.

A long flooding period is on our doorstep

The idea of drought-dominated and flood-dominated periods for the Hawkesbury-Nepean River system was proposed in the mid-1970s by the University of Sydney’s Robin Warner. Since the late 1990’s, it hasn’t been the focus of much research.

Read more: What is a 1 in 100 year weather event? And why do they keep happening so often?

He showed a century-long cycle of alternating periods of dry weather and small floods followed by wet weather and big floods is normal for Sydney. This means the March flood may not have come as a surprise to older residents of the Sackville Bathtub, who have a lived experience of the whole 40-50 year flooding cycle.

As a rough average, one major flood occurred every four years during the last wet-weather period between 1950 and 1990. The largest of this period occurred in November 1961. It filled the Sackville Bathtub to a depth of 15 metres and — like the June 1964 (14.6 metres) and March 1978 (14.5 metres) events — caused more widespread flooding than this year’s flood.

We’re currently 30 years into a dry period, which may be about to end. Conditions might stay dry for another 10 or 20 years.

These cycles are likely caused by natural, long-term “climate drivers” — long-term climatic fluctuations such as El Niño and La Niña, the Pacific Decadal Oscillation and the Indian Ocean Dipole, which are driven by oceanic current circulations. These global phenomena bring both benevolent weather and destructive weather to Australia.

Eastern Australia experiences decades-long periods of wetter weather when these climate drivers sync up with each other. When they’re out of sync, we get dry weather periods.

Read more: A rare natural phenomenon brings severe drought to Australia. Climate change is making it more common

These long-term cycles are natural and have been operating for thousands of years, but climate change is amplifying and accelerating them. Dry periods are getting drier, wet periods are getting wetter.

The good news and bad news

The bad news is that 12-plus metre floods at Hawkesbury River (Windsor Bridge) are not all that unusual. There have been 24, 12-plus metre floods at Windsor Bridge since 1799.

The good news is meteorological forecasters are excellent at predicting when the storms that generate moderate, large and catastrophic floods are coming. We can expect several days’ to a week’s notice of the next big flood.

We can also prepare our individual and communal responses for more large and frequent floods on the Hawkesbury-Nepean. Residents of the area need to think about how they might live near the river as individuals. Decide what is precious and what you will fit into a car and trailer. Practice evacuating.

As a community, we must ensure the transport infrastructure and evacuation protocols minimise disruption to river and floodplain residents while maximising their safety. It’s particularly important we set up inclusive infrastructure to ensure disadvantaged people, who are disproportionately affected by disasters, also have a fighting chance to evacuate and survive.

Read more: Not 'if', but 'when': city planners need to design for flooding. These examples show the way

Upgrading the escape routes that enable people to evacuate efficiently is absolutely vital. As is rethinking whether we should continue urban expansion in the Sackville Bathtub.

So remember, the next major flood is going to occur sooner than we would like. If you live in this region, you must start preparing. Or as a wise elder once said, “Live on a floodplain, own a boat!”

This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. Read the rest of the stories here.

Tom Hubble, Associate Professor, University of Sydney

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

Is Malcolm Turnbull the only Liberal who understands economics and climate science – or the only one who'll talk about it?

Yesterday, former Liberal prime minister Malcolm Turnbull was unceremoniously dumped as chair of the New South Wales government’s climate advisory board, just a week after being offered the role. His crime? He questioned the wisdom of building new coal mines when the existing ones are already floundering.

No-one would suggest building new hotels in Cairns to help that city’s struggling tourism industry. But among modern Liberals it’s patently heresy to ask how rushing to green light 11 proposed coal mines in the Hunter Valley helps the struggling coal industry.

Coal mines in the Hunter are already operating well below capacity and have been laying off workers in the face of declining world demand for coal, plummeting renewable energy prices and trade sanctions imposed by China. The problem isn’t a shortage of supply, but an abundance.

The simple truth is building new coal mines will simply make matters worse, especially for workers in existing coal mines that have already been mothballed or had their output scaled back.

It gets worse. Once an enormous, dusty, noisy open cut coal mine is approved, the agriculture, wine, tourism and horse breeding industries – all major employers in the Hunter Valley – are reluctant to invest nearby. While building new coal mines hurts workers in existing coal mines, the mere act of approving new coal mines harms investment in job creation in the industries that offer the Hunter a smooth transition from coal.

The NSW planning department doesn’t have a plan for how many new coal mines are needed to meet world demand. Nor does it have a plan for how much expansion of rail and port infrastructure is required to meet the output of all the new mines being proposed.

Read more: Forget about the trade spat – coal is passé in much of China, and that's a bigger problem for Australia

That’s why my colleagues and I recently called for a moratorium on new coal mines in the Hunter until such plans were made explicit. Just as you wouldn’t approve 1,000 new homes in a town where the sewerage system was already at capacity, it makes no sense to approve 11 new coal mines in a region that couldn’t export that much coal if it tried.

But if there’s one thing that defines the debate about coal in Australia, its that it makes no sense.

Just as it made no sense for then-treasurer Scott Morrison to wave a lump of coal around in parliament in 2017, it makes no sense for right-wing commentators to pretend approving new mines will help create jobs in coal mining. And it makes no sense for the National Party to ignore the pleas of farmers to protect their land from the damage coal mines do.

On the surface, Turnbull’s support for a pause on approving new mines while a plan is developed is old-fashioned centrism. It protects existing coal workers from new, highly automated mines, it protects farmers and it should make those concerned with climate change at least a bit happy. Win. Win. Win.

But there’s no room for a sensible centre in the Australian coal debate. And when someone even suggests the industry might not be set to grow, its army of loyal parliamentary and media supporters swing into action.

Labor’s Joel Fitzgibbon said Turnbull “wants to make the Upper Hunter a coal-mine-free zone”. The Nationals’ Matt Canavan suggested stopping coal exports was “an inhumane policy to keep people in poverty”. The head of the NSW Minerals Council suggested 12,000 jobs were at risk.

But of course, the opposite is true. Turnbull’s proposal to protect existing coal workers from competition from new mines would save jobs, not threaten them. He didn’t suggest coal mines be shut down tomorrow, or even early. And, given existing coal mines are running so far below capacity, his call has no potential to impact coal exports.

Read more: Labor politicians need not fear: Queenslanders are no more attached to coal than the rest of Australia

Predictably, the Murdoch press ran a relentlessly misleading campaign in support of the coal industry and in opposition to their least favourite Liberal PM. But surprisingly, the NSW government rolled over in record time.

While the government might think appeasing the coal industry will play well among some older regional voters, they must know such kowtowing is a gift to independents such as Zali Steggall, and a fundamental threat to inner-city Liberals such as Dave Sharma, Jason Falinski and Trent Zimmerman.

The decision to dump Turnbull might have bought NSW Premier Gladys Berejiklian some respite from attacks from the Daily Telegraph. But such denial of economics and climate science will provide no respite for existing coal workers in shuttered coal mines or the agriculture and tourism industry that is looking to expand.

No doubt the National Party are pleased with their latest scalp. But it must be remembered this is the party that last year wanted to wage a war against koalas on behalf of property developers. Such political instincts might help the Nationals fend off the threat from One Nation in regional areas but it does nothing to retain votes in leafy Liberal strongholds that deliver most Liberal seats.

Read more: Aren't we in a drought? The Australian black coal industry uses enough water for over 5 million people

Richard Denniss, Adjunct Professor, Crawford School of Public Policy, Australian National University

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

'Failure is not an option': after a lost decade on climate action, the 2020s offer one last chance

In May 2011, almost precisely a decade ago, the government-appointed Climate Commission released its inaugural report. Titled The Critical Decade, the report’s final section warned that to keep global temperature rises to 2℃ this century, “the decade between now and 2020 is critical”.

As the report noted, if greenhouse gas emissions peaked around 2011, the world’s emissions-reduction trajectory would have been easily manageable: net-zero by around 2060, and a maximum emissions reduction rate of 3.7% each year. Delaying the emissions peak by only a decade would require a trebling of this task – a maximum 9% reduction each year.

But, of course, the decade to 2020 did not mark the beginning of the world’s emissions-reduction journey. Global emissions accelerated before dropping marginally under COVID-19 restrictions, then quickly rebounding.

Our new report, released today, shows the immense cost of this inaction. It is now virtually certain Earth will pass the critical 1.5℃ temperature rise this century – most likely in the 2030s. Now, without delay, humanity must focus on holding warming to well below 2℃. For Australia, that means tripling its emissions reduction goal this decade to 75%.

Aim high, go fast

The Climate Council report is titled Aim High: Go Fast: Why Emissions Need To Plummet This Decade. It acknowledges the multiple lines of evidence showing it will be virtually impossible to keep average global temperature rise to 1.5℃ or below this century, without a period of significant overshoot and “drawdown”. (This refers to a hypothetical period in which warming exceeds 1.5℃ then cools back down due to the removal of carbon dioxide (CO₂) from the atmosphere.)

The increasing rate of climate change, insights from past climates, and a vanishing carbon budget all suggest the 1.5℃ threshold will in fact be crossed very soon, in the 2030s.

There is no safe level of global warming. Already, at a global average temperature rise of 1.1℃, we’re experiencing more powerful storms, destructive marine and land heatwaves, and a new age of megafires.

Read more: Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same

As the Intergovernmental Panel on Climate Change has warned, the consequences of breaching 1.5℃ warming will be stark. Heatwaves, droughts, bushfires and intense rain events will become even more severe. Sea levels will rise, species will become extinct and crop yields will fall. Coral reefs, including the Great Barrier Reef, will decline by up to 90%.

And perhaps most frighteningly, overshooting 1.5℃ runs a greater risk of crossing “tipping points”, such as the collapse of ice sheets and the release of natural carbon stores in forests and permafrost. Crossing those thresholds may set off irreversible changes to the global climate system, and destroy critical ecosystems on which life on Earth depends.

Every fraction of a degree matters

The outlook may be dire, but every fraction of a degree of avoided warming matters. Its value will be measured in terms of human lives, species and ecosystems saved. We can, and must, limit warming to well below 2℃. The goal is very challenging, but still achievable.

The strategies, technologies and pathways needed to tackle the climate challenge are now emerging as fast as the risks are escalating. And in the lead-up to the COP26 climate conference in Glasgow later this year, there’s widespread momentum for international cooperation and action.

Read more: Seriously ugly: here's how Australia will look if the world heats by 3°C this century

Many of Australia’s strategic allies and major trading partners – including the United States, Europe, the United Kingdom and China – are starting to move on climate change. But Australia is standing still. This is despite our nation being one of the most vulnerable to climate change – and despite us having some of the world’s best renewable energy resources.

We must urgently grab these opportunities. We propose Australia radically scale up its emissions-reduction targets – to a 75% cut by 2030 from 2005 levels (up from the current 26-28% target). Australia should also aim to reach net-zero emissions by 2035. Doing so by 2050 – a goal Prime Minister Scott Morrison says is his preference – is too late.

A huge but achievable task

Such dramatic action is clearly daunting. There are political, technical and other challenges ahead because action has been delayed. But a 75% emissions-reduction target is a fair and achievable contribution to the global effort.

Australia’s unrivalled potential for renewable energy means it can transform the electricity sector and beyond. Electric vehicles can lead to carbon-free transport and renewably generated electricity and green hydrogen can decarbonise industry.

The emerging new economy is bringing jobs to regional Australia and building cleaner cities by reducing fossil fuel pollution. There is staggering potential for a massive new industry built on the export to Asia of clean energy and products made from clean hydrogen.

Read more: Scott Morrison has embraced net-zero emissions – now it's time to walk the talk

State, territory and local governments are leading the way in this transformation. The federal government must now join the effort.

The transition will no doubt be disruptive at times, and involve hard decisions. Industries such as coal will disappear and others will emerge. This will bring economic and social change which must be managed sensitively and carefully.

But the long-term benefits of achieving a stable climate far outweigh the short-term disruptions. As our report concludes:

The pathway we choose now will either put us on track for a much brighter future for our children, or lock in escalating risks of dangerous climate change. The decision is ours to make. Failure is not an option.

Climate Council researcher Dr Simon Bradshaw contributed to this article.

Will Steffen, Emeritus Professor, Fenner School of Environment & Society, Australian National University

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

Seriously ugly: here's how Australia will look if the world heats by 3°C this century

Imagine, for a moment, a different kind of Australia. One where bushfires on the catastrophic scale of Black Summer happen almost every year. One where 50℃ days in Sydney and Melbourne are common. Where storms and flooding have violently reshaped our coastlines, and unique ecosystems have been damaged beyond recognition – including the Great Barrier Reef, which no longer exists.

Frighteningly, this is not an imaginary future dystopia. It’s a scientific projection of Australia under 3℃ of global warming – a future we must both strenuously try to avoid, but also prepare for.

The sum of current commitments under the Paris climate accord puts Earth on track for 3℃ of warming this century. Research released today by the Australian Academy of Science explores this scenario in detail.

The report, which we co-authored with colleagues, lays out the potential damage to Australia. Unless the world changes course and dramatically curbs greenhouse gas emissions, this is how bad it could get.

A spotlight on the damage

Nations signed up to the Paris Agreement collectively aim to limit global warming to well below 2℃ this century and to pursue efforts to limit temperature increase to 1.5℃. But on current emissions-reduction pledges, global temperatures are expected to far exceed these goals, reaching 2.9℃ by 2100.

Australia is the driest inhabited continent, and already has a highly variable climate of “droughts and flooding rains”. This is why of all developed nations, Australia has been identified as one of the most vulnerable to climate change.

The damage is already evident. Since records began in 1910, Australia’s average surface temperature has warmed by 1.4℃, and its open ocean areas have warmed by 1℃. Extreme events – such as storms, droughts, bushfires, heatwaves and floods – are becoming more frequent and severe.

Today’s report brings together multiple lines of evidence such as computer modelling, observed changes and historical paleoclimate studies. It gives a picture of the damage that’s already occurred, and what Australia should expect next. It shines a spotlight on four sectors: ecosystems, food production, cities and towns, and health and well-being.

In all these areas, we found the impacts of climate change are profound and accelerating rapidly.

Read more: Yes, Australia is a land of flooding rains. But climate change could be making it worse

1. Ecosystems

Australia’s natural resources are directly linked to our well-being, culture and economic prosperity. Warming and changes in climate have already eroded the services ecosystems provide, and affected thousands of species.

The problems extend to the ocean, which is steadily warming. Heat stress is bleaching and killing corals, and severely damaging crucial habitats such as kelp forests and seagrass meadows. As oceans absorb carbon dioxide (CO₂) from the atmosphere, seawater is reaching record acidity levels, harming marine food webs, fisheries and aquaculture.

At 3℃ of global warming by 2100, oceans are projected to absorb five times more heat than the observed amount accumulated since 1970. Being far more acidic than today, ocean oxygen levels will decline at ever-shallower depths, affecting the distribution and abundance of marine life everywhere. At 1.5-2℃ warming, the complete loss of coral reefs is very likely.

Read more: The oceans are changing too fast for marine life to keep up

Under 3℃ warming, global sea levels are projected to rise 40-80 centimetres, and by many more metres over coming centuries. Rising sea levels are already inundating low-lying coastal areas, and saltwater is intruding into freshwater wetlands. This leads to coastal erosion that amplifies storm impacts and affects both ecosystems and people.

Land and freshwater environments have been damaged by drought, fire, extreme heatwaves, invasive species and disease. An estimated 3 billion vertebrate animals were killed or displaced in the Black Summer bushfires. Some 24 million hectares burned, including 80% of the Blue Mountains World Heritage Area and 50% of Gondwana rainforests. At 3℃ of warming, the number of extreme fire days could double.

Some species are shifting to cooler latitudes or higher elevations. But most will struggle to keep up with the unprecedented rate of warming. Critical thresholds in many natural systems are likely to be exceeded as global warming reaches 1.5℃. At 2℃ and beyond, we’re likely to see the complete loss of coral reefs, and inundation of iconic ecosystems such as the World Heritage-listed Kakadu National Park.

At 3℃ of global warming, Australia’s present-day ecological systems would be unrecognisable. The first documented climate-related global extinction of a mammal, the Bramble Cay melomys from the Torres Strait, is highly unlikely to be the last. Climate change is predicted to increase extinction rates by several orders of magnitude.

Degradation of Australia’s unique ecosystems will harm the tourism and recreation industries, as well as our food security, health and culture.

There are ways to reduce the climate risk for ecosystems – many of which also benefit humans. For example, preserving and restoring mangroves protects our coasts from storms, increases carbon storage and retains fisheries habitat.

Read more: Click through the tragic stories of 119 species still struggling after Black Summer in this interactive (and how to help)

2. Food production

Australian agriculture and food security already face significant risks from droughts, heatwaves, fires, floods and invasive species. At 2℃ or more of global warming, rainfall will decline and droughts in areas such as southeastern and southwestern Australia will intensify. This will reduce water availability for irrigated agriculture and increase water prices.

Heat stress affects livestock welfare, reproduction and production. Projected temperature and humidity changes suggest livestock will experience many more heat stress days each year. More frequent storms and heavy rainfall are likely to worsen erosion on grazing land and may lead to livestock loss from flooding.

Heat stress and reduced water availability will also make farms less profitable. A 3℃ global temperature increase would reduce yields of key crops by between 5% and 50%. Significant reductions are expected in oil seeds (35%), wheat (18%) and fruits and vegetables (14%).

Climate change also threatens forestry in hotter, drier regions such as southwestern Australia. There, the industry faces increased fire risks, changed rainfall patterns and growing pest populations. In cooler regions such as Tasmania and Gippsland, forestry production may increase as the climate warms. Existing plantations would change substantially under 3℃ warming.

As ocean waters warm, distributions and stock levels of commercial fish species are continuing to change. This will curb profitability. Many aquaculture fisheries may fundamentally change, relocate or cease to exist.

These changes may cause fisheries workers to suffer unemployment, mental health issues (potentially leading to suicides) and other problems. Strategic planning to create new business opportunities in these regions may reduce these risks.

Read more: Australia's farmers want more climate action – and they’re starting in their own (huge) backyards

3. Cities and towns

Almost 90% of Australians live in cities and towns and will experience climate change in urban environments.

Under a sea level rise of 1 metre by the end of the century – a level considered plausible by federal officials – between 160,000 and 250,000 Australian properties and infrastructure are at risk of coastal flooding.

Strategies to manage the risk include less construction in high-risk areas, and protecting coastal land with sea walls, sand dunes and mangroves. But some coastal areas may have to be abandoned.

Extreme heat, bushfires and storms put strain on power stations and infrastructure. At the same time, more energy is needed for increased air conditioning use. Much of Australia’s electricity generation relies on ageing and unreliable coal-fired power stations. Extreme weather can also disrupt and damage the oil and gas industries. Diversifying energy sources and improving infrastructure will be important to ensure reliable energy supplies.

The insurance and financial sector is becoming increasingly aware of climate risk and exposure. Insurance firms face increased claims due to climate-related disasters including floods, cyclones and mega-fires. Under some scenarios, one in every 19 property owners face unaffordable insurance premiums by 2030. A 3℃ world would render many more properties and businesses uninsurable.

Cities and towns, however, can be part of the climate solution. High-density urban living leads to a lower per capita greenhouse gas emission “footprint”. Also, innovative solutions are easier to implement in urban environments.

Passive cooling techniques, such as incorporating more plants and street trees during planning, can reduce city temperatures. But these strategies may require changes to stormwater management and can take time to work.

Read more: When climate change and other emergencies threaten where we live, how will we manage our retreat?

4. Human health and well-being

A 3℃ world threatens human health, livelihoods and communities. The elderly, young, unwell, and those from disadvantaged socioeconomic backgrounds are at most risk.

Heatwaves on land and sea are becoming longer, more frequent and severe. For example, at 3℃ of global warming, heatwaves in Queensland would happen as often as seven times a year, lasting 16 days on average. These cause physiological heat stress and worsen existing medical conditions.

Bushfire-related health impacts are increasing, causing deaths and exacerbating pre-existing conditions such as heart and lung disease. Tragically, we saw this unfold during Black Summer. These extreme conditions will increase at 2℃ and further at 3℃, causing direct and indirect physical and mental health issues.

Under 3℃ warming, climate damage to businesses will likely to lead to increased unemployment and possibly higher suicide rates, mental health issues and health issues relating to heat stress.

At 3°C global warming, many locations in Australia would be very difficult to inhabit due to projected water shortages.

As weather patterns change, transmission of some infectious diseases, such as Ross River virus, will become more intense. “Tropical” diseases may spread to more temperate areas across Australia.

Strategies exist to help mitigate these effects. They include improving early warning systems for extreme weather events and boosting the climate resilience of health services. Nature-based solutions, such as increasing green spaces in urban areas, will also help.

Read more: How does bushfire smoke affect our health? 6 things you need to know

How to avoid catastrophe

The report acknowledges that limiting global temperatures to 1.5℃ this century is now extremely difficult. Achieving net-zero global emissions by 2050 is the absolute minimum required to to avoid the worst climate impacts.

Australia is well positioned to contribute to this global challenge. We have a well-developed industrial base, skilled workforce and vast sources of renewable energy.

But Australia must also pursue far more substantial emissions reduction. Under the Paris deal, we’ve pledged to reduce emissions by 26-28% between 2005 and 2030. Given the multiple and accelerating climate threats Australia faces, we must scale up this pledge. We must also display the international leadership and collaboration required to set Earth on a safer climate trajectory.

Our report recommends Australia immediately do the following:

1. join global leaders in increasing actions to urgently tackle and solve climate change

2. develop strategies to meet the challenges of extreme events that are increasing in intensity, frequency and scale

3. improve our understanding of climate impacts, including tipping points and the compounding effects of multiple stressors at global warming of 2℃ or more

4. systematically explore how food production and supply systems should prepare for climate change

5. better understand the impacts and risks of climate change for the health of Australians

6. introduce policies to deliver deep and rapid cuts in emissions across the economy

7. scale up the development and implementation of low- to zero-emissions technologies

8. review Australia’s capacity and flexibility to take up innovations and technology breakthroughs for transitioning to a low-emissions future

9. develop a better understanding of climate solutions through dialogue with Aboriginal and Torres Strait Islander peoples – particularly strategies that helped people manage Australian ecosystems for tens of thousands of years

10. continue to build adaptation strategies and greater commitment for meeting the challenges of change already in the climate system.

We don’t have much time to avert catastrophe. This decade must be transformational, and one where we choose a safer future.

The report upon which this article is based, The Risks to Australia of a 3°C Warmer World, was authored and reviewed by 21 experts.

Read more: Climate crisis: keeping hope of 1.5°C limit alive is vital to spurring global action

Ove Hoegh-Guldberg, Professor, The University of Queensland and Lesley Hughes, Professor, Department of Biological Sciences, Macquarie University

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

Like the ocean’s ‘gut flora’: we sailed from Antarctica to the equator to learn how bacteria affect ocean health

Aboard an Australian research vessel, the RV Investigator, we sailed for 63 days from Antarctica’s ice edge to the warm equator in the South Pacific and collected 387 water samples.

Our goal? To determine how the genetic code of thousands of different micro-organisms can provide insights into the ocean’s functional diversity — the range of tasks performed by bacteria in the ocean.

Our research was published yesterday in Nature Communications. It showed how bacteria can help us measure shifts in energy production at the base of the food web. These results are important, as they highlight an emerging opportunity to use genetic data for large-scale ecosystem assessments in different marine environments.

In light of our rapidly changing climate, this kind of information is critical, as it will allow us to unpack the complexity of nature step by step. Ultimately, it will help us mitigate human pressures to protect and restore our precious marine ecosystems.

Why should we care about marine bacteria?

The oceans cover 71% of our planet and sustain life on Earth. In the upper 100 meters, the sunlit part of the oceans, microscopic life is abundant. In fact, it’s responsible for producing up to 50% of all the oxygen in the world.

Much like the link recently established between human health and the human microbiome (“gut flora”), ocean health is largely controlled by its bacterial inhabitants.

But the role of bacteria go beyond oxygen production. Bacteria sustain, inject and control the fluxes of energy, nutrients and organic matter in our oceans. They provide the energy and food for the entire marine food web, from tiny crustaceans to fish larvae, whales and the fish we eat.

These micro-organisms also execute key roles in numerous biogeochemical cycles (the carbon, nitrogen, phosphorus, sulphur and iron cycles, to name a few).

So, it’s important to quantify their various tasks and understand how the different bacterial species and their functions respond to environmental changes.

Fundamental questions

Global ocean research initiatives — such as GO-SHIP and GEOTRACES — have been measuring the state of oceans in expeditions like ours for decades. They survey temperature, salinity, nutrients, trace metals (iron, cobalt and more) and other essential ocean variables.

Only recently, however, have these programs begun measuring biological variables, such as bacterial gene data, in their global sampling expeditions.

Including bacterial gene data to measure the state of the ocean means we can try to fill critical knowledge gaps about how the diversity of bacteria impacts their various tasks. One hypothesis is whether a greater diversity of bacteria leads to a better resilience in an ecosystem, allowing it to withstand the effects of climate change.

In our paper, we addressed a fundamental question in this global field of marine microbial ecology: what is the relationship between bacterial identity and function? In other words, who is doing what?

What we found

We showed it’s possible to link the genetic code of marine bacteria to the various functions and tasks they execute, and to quantify how these functions changed from Antarctica to the equator.

The functions that changed include taking in carbon dioxide from the atmosphere, bacterial growth, strategies to cope with limited nutrients, and breaking down organic matter.

Read more: Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event

Another key finding is that “oceanographic fronts” can act as boundaries within a seemingly uniform ocean, resulting in unique assemblages of bacteria with specific tasks. Oceanographic fronts are distinct water masses defined by, for instance, sharp changes in temperature and salinity. Where the waters meet and mix, there’s high turbulence.

The change we recorded in energy production across the subtropical front, which separates the colder waters from the Southern Ocean from the warmer waters in the tropics, was a clear example of how oceanographic fronts influenced bacterial functions in the ocean.

Tracking changes in our ecosystems

As a result of our research, scientists may start using the functional diversity of bacteria as an indicator to track changes in our ecosystems, like canaries in a coal mine.

Read more: Half of global methane emissions come from aquatic ecosystems – much of this is human-made

So the functional diversity of bacteria can be used to measure how human growth and urbanisation impact coastal areas and estuaries.

For example, we can more accurately and holistically measure the environmental footprint of aquaculture pens, which are known to affect water quality by increasing concentrations of nutrients such as carbon, nitrogen and phosphorus – all favourite elements utilised by bacteria.

Likewise, we can track changes in the environmental services rendered by estuaries, such as their important role in removing excessive nitrogen that enters the waterways due to agriculture run-off and urban waste.

With 44% of the world’s population living along coastlines, the input of nitrogen to marine ecosystems, including estuaries, is predicted to increase, putting a strain on the marine life there.

Ultimately, interrogating the bacterial diversity using gene data, along with the opportunity to predict what this microscopic life is or will be doing in future, will help us better understand nature’s complex interactions that sustain life in our oceans.

Read more: Humans are polluting the environment with antibiotic-resistant bacteria, and I'm finding them everywhere

Eric Jorden Raes, Postdoctoral researcher Ocean Frontier Institute, Dalhousie University

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

Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event

The tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the poles.

Ecologists have assumed this global pattern has remained stable over recent centuries — until now. Our recent study found the ocean around the equator has already become too hot for many species to survive, and that global warming is responsible.

In other words, the global pattern is rapidly changing. And as species flee to cooler water towards the poles, it’s likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.

The bell curve is warping dangerously

This global pattern — where the number of species starts lower at the poles and peaks at the equator — results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.

So, as our oceans warm, species have tracked their preferred temperatures by moving towards the poles. Although the warming at the equator of 0.6℃ over the past 50 years is relatively modest compared with warming at higher latitudes, tropical species have to move further to remain in their thermal niche compared with species elsewhere.

As ocean warming has accelerated over recent decades due to climate change, the dip around at the equator has deepened.

We predicted such a change five years ago using a modelling approach, and now we have observational evidence.

Read more: The ocean is becoming more stable – here's why that might not be a good thing

For each of the 10 major groups of species we studied (including pelagic fish, reef fish and molluscs) that live in the water or on the seafloor, their richness either plateaued or declined slightly at latitudes with mean annual sea-surface temperatures above 20℃.

Today, species richness is greatest in the northern hemisphere in latitudes around 30°N (off southern China and Mexico) and in the south around 20°S (off northern Australia and southern Brazil).

This has happened before

We shouldn’t be surprised global biodiversity has responded so rapidly to global warming. This has happened before, and with dramatic consequences.

252 million years ago…

At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10℃ over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.

A 2020 study of the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.

125,000 years ago…

A 2012 study showed that more recently, during the rapid warming around 125,000 years ago, there was a similar swift movement of reef corals away from the tropics, as documented in the fossil record. The result was a pattern similar to the one we describe, although there was no associated mass extinction.

Authors of the study suggested their results might foreshadow the effects of our current global warming, ominously warning there could be mass extinctions in the near future as species move into the subtropics, where they might struggle to compete and adapt.

Today…

During the last ice age, which ended around 15,000 years ago, the richness of forams (a type of hard-shelled, single-celled plankton) peaked at the equator and has been dropping there ever since. This is significant as plankton is a keystone species in the foodweb.

Our study shows that decline has accelerated in recent decades due to human-driven climate change.

The profound implications

Losing species in tropical ecosystems means ecological resilience to environmental changes is reduced, potentially compromising ecosystem persistence.

In subtropical ecosystems, species richness is increasing. This means there’ll be species invaders, novel predator-prey interactions, and new competitive relationships. For example, tropical fish moving into Sydney Harbour compete with temperate species for food and habitat.

This could result in ecosystem collapse — as was seen at the boundary between the Permian and Triassic periods — in which species go extinct and ecosystem services (such as food supplies) are permanently altered.

The changes we describe will also have profound implications for human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, potentially beyond sovereign waters of island nations.

Read more: Tropical fisheries: does limiting international trade protect local people and marine life?

Similarly, many reef species important for artisanal fishers — and highly mobile megafauna such as whale sharks, manta rays and sea turtles that support tourism — are also likely to move toward the subtropics.

The movement of commercial and artisanal fish and marine megafauna could compromise the ability of tropical nations to meet the Sustainable Development Goals concerning zero hunger and marine life.

Is there anything we can do?

One pathway is laid out in the Paris Climate Accords and involves aggressively reducing our emissions. Other opportunities are also emerging that could help safeguard biodiversity and hopefully minimise the worst impacts of it shifting away from the equator.

Currently 2.7% of the ocean is conserved in fully or highly protected reserves. This is well short of the 10% target by 2020 under the UN Convention on Biological Diversity.

But a group of 41 nations is pushing to set a new target of protecting 30% of the ocean by 2030.

This “30 by 30” target could ban seafloor mining and remove fishing in reserves that can destroy habitats and release as much carbon dioxide as global aviation. These measures would remove pressures on biodiversity and promote ecological resilience.

Designing climate-smart reserves could further protect biodiversity from future changes. For example, reserves for marine life could be placed in refugia where the climate will be stable over the foreseeable future.

We now have evidence that climate change is impacting the best-known and strongest global pattern in ecology. We should not delay actions to try to mitigate this.

This story is part of Oceans 21
Our series on the global ocean opened with five in-depth profiles. Look out for new articles on the state of our oceans in the lead-up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.

Read more: Australia's marine (un)protected areas: government zoning bias has left marine life in peril since 2012

Anthony Richardson, Professor, The University of Queensland; Chhaya Chaudhary, , University of Auckland; David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast, and Mark John Costello, Professor, University of Auckland

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

Climate change is a security threat the government keeps ignoring. We'll show up empty handed to yet another global summit

Climate change is a hot topic in Australian security circles, as it poses an emerging threat to our national resilience and way of life. As a new report from the Australian Strategic Policy Institute (ASPI) last week warned, the federal government is unprepared to meet these challenges.

The report, authored by Dr Robert Glasser, said the government has largely overlooked the security threat posed by rising seas, climate-induced famine, extreme weather events, mass migrations and other climate change damage in Southeast Asia. Australia is sitting on the frontline of this vulnerable region.

Glasser’s report focuses on Southeast Asia, but in the bigger picture, climate security is an existential global risk which the Australian government is yet to fully grasp. It is this global aspect of climate and security which will be on the agenda in two weeks time at the Biden Leaders Summit in the US.

Why should we be worried?

The global risk is broader than traditional security threats, such as the rise of China, terrorism and separatist movements. As the ASPI report emphasises, there is a relationship between climate security and other sectors such as food, health and environmental security.

Unlike traditional national security threats, climate threats have no respect for national or sector borders and cannot be solved with missiles.

The threat is urgent. With the end of the Donald Trump presidency, climate change is back on regional and international security action agendas. The penny has dropped on how little time is left to take action to prepare for the worst of consequences.

This is especially the case when there are long lead times to implement action, such as infrastructure development and military capability development.

Read more: Climate change poses a 'direct threat' to Australia's national security. It must be a political priority

ASPI’s key recommendations to the government include:

• improving understanding of climate change risks through a broad whole-of-government process

• building capacity in government agencies to assess ongoing risks

• identifying opportunities for regional aid and investments.

These make sense, as the first step of preparedness is understanding the risk.

Security risks go beyond natural disasters

The ASPI report notes Southeast Asia “has the world’s highest sea-level rise per kilometre of coastline and the largest coastal population affected by it”. The region is a hot spot for cyclones, with some nations vulnerable to catastrophic heat or fires.

The ASPI report notes:

Those hazards will not only exacerbate the traditional regional security threats […] but also lead to new threats and the prospect of multiple, simultaneous crises, including food insecurity, population displacement and humanitarian disasters that will greatly test our national capacities, commitments and resilience.

The report focuses on Southeast Asia and natural disasters, but the risks and the affected regions are bigger than that.

The Indo-Pacific region may see the displacement of millions of people due to climate change-related extreme weather events, heatwaves, droughts, rising seas and floods. We’re already seeing this occur in Bangladesh and small island developing states.

We could also see conflict arise as climate change affects global food or water resources. A particular concern is the potential geopolitical tensions between India and China over dwindling Tibetan water resources.

Australia is getting left behind

Urgency and risk are central to an executive order from President Joe Biden in January. The order requires a US national security estimate on the economic and national security impacts of climate change by June. The US Department of Defence must also complete an analysis of the security implications of climate change in the same timeframe.

Read more: Biden says the US will rejoin the Paris climate agreement in 77 days. Then Australia will really feel the heat

Most tellingly, the US is taking an integrated approach to climate security. Foreign policy, defence and economic risk analysis are being conducted in a joined-up, systemic way.

In contrast, the Australian Defence Strategic Update 2020 was conducted in isolation from foreign policy and economic reviews. Taking a narrow military perspective, it does mention climate change, but only once, as a subset of human security threats.

Australia risks being left behind as other countries follow the US lead. Across the Tasman, our Kiwi friends are already well advanced in turning risk awareness into action. The New Zealand government completed its first national climate risk assessment last year, with a national adaptation plan to be completed by August 2022.

What are the consequences?

Being left behind has consequences for Australia’s international standing, national resilience and economic position.

From a diplomatic perspective, Australia’s influence in the Indo-Pacific region is diminished, relative to other actors, especially in states where climate change risk is a top priority, such as Vanuatu or Kiribati.

Risks offer opportunities as well. For example, Australia has an abundance of critical minerals and rare earths needed for modern communications, space technologies, and renewable energy generation and transmission. These are key for business, as well as critical for defence forces.

Read more: Critical minerals are vital for renewable energy. We must learn to mine them responsibly

However, processing and manufacturing is largely conducted offshore — in countries vulnerable to climate risks such as Malaysia — before returning to Australia as finished products.

This puts Australian defence and space and energy sectors at risk of disruption, and Australian businesses at risks of economic loss.

What needs to happen next?

ASPI’s report echoes the earlier recommendation from a 2018 Senate inquiry into the implications of climate change for Australia’s national security. The inquiry also called for a coordinated whole-of-government response to climate change risks.

Three years later, the federal government has yet to act on its recommendations.

The Australian government now needs to have a greater sense of urgency to act on the growing national and international calls to act on climate risk. But first, our leaders need a changed mindset. They must accept that climate change is an immediate threat to Australia.

Read more: Senate report: climate change is a clear and present danger to Australia's security

Cheryl Durrant, Adjunct Associate Professor, UNSW

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