07/03/2022

(The Conversation) Climate Change: Effect On Forests Could Last Millennia, Ancient Ruins Suggest

The Conversation -  | 

Forest plants can’t keep up with the speed at which the climate is changing.


Authors
  •  is Senior Researcher in Ecology & Biostatistics (CNRS), Université de Picardie Jules Verne (UPJV)
  •  is Research Fellow and Lecturer, School of Biological Sciences, University of Bristol     
Forests are home to 80% of land-based biodiversity, but these arks of life are under threat.

The rising average global temperature is forcing tiny plants like sidebells wintergreen on the forest floor (known as the understory) to shift upslope in search of cooler climes.

Forest plants can’t keep up with the speed at which the climate is changing – they lag behind.

The pace at which forests adapt to changing conditions is so slow that species living in forest understories today are probably responding to more ancient changes in their environment.

For instance, the Mormal Forest floor in northern France is, in several places, covered by a carpet of quaking sedge. This long grass-like plant betrays the former settlements of German soldiers who used it to make straw mattresses during the first world war.

Changes in how people managed the land, sometimes dating back to the Middle Ages or even earlier, leave a lasting fingerprint on the biodiversity of forest understories.

Knowing how long the presence of a given species can carry on the memory of past human activities can tell scientists how long climate change is likely to have an influence.

The wind whispering through Mormal’s sedge evokes the region’s wartime past. Jonathan Lenoir, Author provided
Ecologists are turning to technologies such as lidar to rewind the wheel of time.

Lidar works on the same principles as radar and sonar, using millions of laser pulses to analyse echoes and generate detailed 3D reconstructions of the surrounding environment. This is what driverless cars use to sense and navigate the world.

Since the late 1990s, lidar has enabled amazing discoveries, such as the imprints of Mayan civilisation preserved beneath the canopy of tropical forest.

In a new paper, I, along with experts in ecology, history, archaeology and remote sensing, used lidar to trace human activity in the Compiègne Forest in northern France back to Roman times – much later than historical maps could ever do.

Illuminating ghosts from the past

Compared to farm fields, which are ceaselessly disturbed, forest floors tend to be well-preserved environments. As a result, the ground below the forest canopy may still bear the imprints of ancient human occupation.

Archaeologists know this pretty well and they increasingly rely on lidar technology as a prospecting tool. It allows them to virtually remove all the trees from aerial images and hunt artefacts hidden below treetops and fossilised under forest floors.

Using airborne lidar data acquired in 2014 over the Compiègne Forest in northern France, a team of archaeologists and historians found well-preserved Roman settlements, farm fields and roads.

Long considered a remnant of prehistoric forest, the Compiègne was, in fact, a busy agricultural landscape 1,800 years ago.

Lidar can reveal the terrain hidden beneath forests. Jonathan Lenoir, Author provided

A closer look at these ghostly images of the Compiègne Forest reveals several depressions within a fossilised network of Roman farm fields.

Archaeologists excavated numerous depressions like this across many forests in north-eastern France and found that people from the late iron age and Roman era carved them.

These depressions were made to extract marls (lime-rich mud) to enrich farm fields in carbonate minerals for growing crops and to create local depressions where rainwater collects naturally for livestock to drink.

Marling is still a widespread practice in crop production in northern France.

A pit for extracting marl in Northern France. Jonathan Lenoir, Author provided
The long-lasting effects of human activity

These signs of Roman occupation in modern forests provide clues to why some plant species are present where we wouldn’t expect them to be.

On a summer day in 2007 in a corner of the Tronçais Forest in central France, a team of botanists found a little patch of nitrogen-loving species – blue bugle, woodland figwort and stinging nettle – nestled among more acid-loving plants.

Nothing special at first sight. Until archaeologists found that Roman farm buildings had once stood in that spot, with cattle manure probably enriching the soil in phosphorous and nitrogen.

Blue bugle heralds an ancient Roman farm. Kateryna Pavliuk/Shutterstock

If a clutch of tiny plants can betray ancient farming practices dating back centuries or millennia, ongoing environmental changes, such as climate change, will have similarly long-lasting effects.

Even if the Earth stopped heating, the biodiversity of its forests would continue changing in response to the warming signal, in a delayed manner, through the establishment of more and more warm-loving species for several centuries into the future.

Just as the Intergovernmental Panel on Climate Change has a mission to provide plausible scenarios on future climate change, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services aims to provide plausible scenarios on the fate of biodiversity.

Yet none of the biodiversity models so far incorporate this lag effect. This means that model predictions are more prone to errors in forecasting the fate of biodiversity under future climate change.

Knowing about the past of modern forests can help decode their present state and model their future biodiversity. Now lidar technology is there to help ecologists travel back in time and explore the forest past.

Improving the accuracy of predictions from biodiversity models by incorporating lagging dynamics is a big challenge, but it is a necessary endeavour for more effective conservation strategies.

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(AU ABC) Worse Weather And More Floods: The IPCC Report Contains Warnings Australia Should Heed

ABC News - Michael Slezak

This 7.30 report looks at the IPCC's warnings that health risks are intensified by climate change. (Jess Davis)

This week we saw large parts of the country engulfed by flood waters.

People fleeing torrents raging through their living rooms, others wading neck-deep across rivers that were once roads. Some clung to their roofs, dotted like islands in a sea of murky brown, others rescued by neighbours in dinghies.

Some were trapped by landslides. Some even lost their lives.

This week, we also saw the world's most comprehensive analysis of what climate change was doing to us. How it's going to get worse, and what we can do to prepare.
Climate change warnings
The IPCC says climate change is now a threat to human wellbeing, warning the window we have to act is "rapidly closing". Read more
Set against the backdrop of some of the worst floods and heaviest rainfalls in Australian history, the findings of the Intergovernmental Panel on Climate Change (IPCC) were both bleak, and shocking.

UN Secretary-General Antonio Guterres described it as "an atlas of human suffering" and laid the blame squarely at world leaders, calling it "a damning indictment of failed climate leadership".

The response from world leaders was mixed — ranging from urgent concern to deflection and complete silence.

What did the report say about how climate change will affect humans? The 2,600-page report's findings are about as bad as you could imagine.

Climate change is already upending the lives of billions of people around the world and will definitely get worse over the coming years and decades.

Continuing warming — and worsening impacts — are inevitable, with some of those impacts beyond our ability to adapt.

For example, the increasing heat will kill hundreds more people in Melbourne, Sydney and Brisbane, no matter what. But it will kill hundreds more again, if we don't act quickly to cut emissions.

The projections about future flooding are incredibly worrying. The report says with sea level rise of just 0.5m — which we will likely see this century, and maybe as soon as 2050 — what is currently considered a "one-in-100-year flood event" could happen "several times a year".

The report also notes flash flooding is going to become more common as downpours become more intense. (Supplied: Sue Higginson)
Some coastal areas will be lost to sea level rise, which will be made worse by more intense storm surges. In some cases the report says there is no serious option but retreat.

Mapping tools can easily reveal how rising seas will inundate coastal areas. Coastal Risk Australia is one such tool.

It shows that sea level rise by 2100 — if we don't move to quickly cut emissions — huge parts of Cairns will be inundated.

By 2100, sea levels may rise by 0.84m. This map shows what that'd look like in Cairns.(Supplied: Coastal Risk Australia)
Byron Bay will also see large parts flooded at high tide, as would Noosa.

If we cut emissions now, we delay that amount of sea level rise for some time, giving us perhaps decades to prepare. 

But in the longer term, we will see sea level rise for centuries, according to report author Mark Howden, head of the ANU Institute for Climate, Energy and Disaster Solutions.

And there are serious worries, he says, that we might already have triggered some tipping points that will make sea level rise much faster.

When it reaches 5 metres, huge parts of all our capital cities will be under water.

Longer term, if sea levels rose by 5m, huge parts of most capital cities like Sydney (pictured) would be underwater. (Supplied: Coastal Risk Australia)
No matter what we do with emissions, the Great Barrier Reef is going to see bleaching conditions every year this century — although we can delay that by about a decade by cutting emissions.

The ecosystems Australia's set to lose
Some of Australia's iconic and unique natural ecosystems are headed for irreversible damage if we keep emitting carbon at current rates, climate experts warn. Read more
The heat stress will be made worse by heavy rainfall, which will push pollution onto the reef.

And while we can spend billions to protect small patches of the reef, none of that is going to stop widespread bleaching.

Even if we limit warming to 1.5C, scientists have estimated 90 per cent of the reef could be killed. Beyond that, there would be virtually nothing left.

Some alpine forests and the animals that depend on them are already near the point of no return, and with inevitable ongoing warming may not survive. The report says with immediate cuts to greenhouse gases, we can save more of the alpine ecosystems.

What needs to be done? The report found the window of opportunity to take the required action was rapidly closing but there was still time to avoid the worst ravages of climate change.

Keeping warming at 1.5C wouldn't stop increased disruption, but would, for example, save hundreds of Australians' lives each year from heat-related deaths and allow the economy to grow to 2070 rather than shrink.

Antonio Guterres was clear about what we needed to do to achieve that.

"Science tells us that will require the world to cut emissions by 45 per cent by 2030 and achieve net zero emissions by 2050," he said.

"But according to current commitments, global emissions are set to increase almost 14 per cent over the current decade."

Youtube Antonio Guterres described the IPCC's latest report as "an atlas of human suffering".

But because even 1.5C of warming will involve huge impacts on society, we also need to start to prepare.

Adaptation is complex and needs to be progressed by all levels of government and society. What it will involve will be different for different locations, different sectors and different communities.

In some places it will involve levees to hold back water, or a "managed retreat" from the coast. In other places it will involve new planning rules about what sorts of buildings can be built.

The report emphasised that those that were the most vulnerable to climate change were also those who were the least able to adapt: the world's poor. So a big part of adapting to climate change is addressing the gap between rich and poor.

What did the Australian government say about the report? The Australian government had very little to say about the report. There were no widely distributed press releases by the Environment Minister, the Emissions Reduction Minister or the Prime Minister.

Minister Bridget McKenzie holds the portfolio for Recovery and Resilience — one that is highly relevant to the IPCC report.

In an interview, she accepted climate change was making events like the floods this week more frequent and intense, and accepted that this was a result of the failure of leaders.

"The IPCC is dead right. There has been a lack of leadership," she said.

Bridget McKenzie said there had been a lack of leadership on climate change, globally.

But she denied that the Morrison government itself had demonstrated any lack of leadership.

When the ABC approached environment minister Sussan Ley's office for a response to the findings of the report, we were given a statement from a "Morrison Government spokesperson" that celebrated Australia's action on climate.

It argued Australia was reducing emissions faster than many comparable countries, spending a record amount on adaptation and had agreed to a net-zero by 2050 target – with a "detailed" plan.

All these points were disputed by experts contacted by the ABC.

The report says some ecosystems will degrade, and there’s not much we can do about it.(Supplied: Great Barrier Reef Legacy, File photo)
"Australia is consistently ranked dead last based on our weak climate performance," said Will Steffen, a climate scientist at the Climate Council.
"This government's failings on this critical issue will go down as the defining policy and leadership failure of the past decade.
"Australia has the highest emissions per capita and per unit of GDP among wealthy developed nations.

"The Morrison government announced a net zero by 2050 target but this isn't backed up by any credible policies. The Morrison government's own modelling shows it won't even come close to reaching this far away, vague goal."

What about the Opposition and other leaders? Labor was more vocal about the report. Its spokesperson on climate and energy, Chris Bowen, described the report as a "stark warning which is particularly relevant to Australians," and said a strong response to climate change could boost our economy.

He said the events showed the stronger 2030 emissions reduction targets promised by Labor — 43 per cent compared to the government's 26 per cent — and Labor's Powering Australia plan, which includes ambitious plans for renewable energy, improved energy transmission and electric vehicles, were desperately needed.

The Greens put out a very detailed press release on the report and sought media coverage.

"This report leaves no room for argument. If we want to stop dangerous climate change, we need to keep coal and gas in the ground," Greens leader Adam Bandt said.

"Delay is the new denial. We can't wait until 2050, and anything less than a rapid phase-out of coal and gas means giving up on the 1.5 degrees goal in the Paris Agreement."

Some global leaders were on the front-foot talking about the report.

John Kerry, the US special presidential envoy for climate, said the report "paints a dire picture of the impacts already occurring because of a warmer world and the terrible risks to our planet if we continue to ignore science".

And former leaders of small island nations were exasperated. Anote Tong, former president of Kiribati, said: "The IPCC report confirms what people in Kiribati already knew: sea levels are rising fast and growing climate change impacts such as flooding and higher king tides are endangering our very ability to continue living on our ancestral homelands."

Large parts of island nation Kiribati will become inhabitable with rising sea levels.(Supplied: Your Brother, Your Sister/Darren James)
Professor Steffen urged Australia to lead on climate change.

"We have so much to lose as a nation if we don't start taking climate change seriously, and so much to gain if we do, as one of the sunniest and windiest countries on Earth," he said.

"Amongst wealthy, developed nations, we need to be a global leader on climate change, not its biggest laggard."

The IPCC report itself makes a similar point in no less urgent language.

"Any further delay in concerted anticipatory global action on adaptation and mitigation will miss a brief and rapidly closing window of opportunity to secure a liveable and sustainable future for all," it said.

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(SMH) International Women’s Day Highlights Climate Justice As A Feminist Issue

Sydney Morning Herald - Caitlin Fitzsimmons

Women are on the front lines of the global climate crisis, making up 80 per cent of the 21.5 million people displaced every year by climate-related events.

That’s according to the United Nations, which predicts at least 1.2 billion people could be displaced by climate events every year by 2050.

Kavita Naidu, an international human rights lawyer and activist from Fiji, specialising in climate justice. Credit: James Brickwood

Women and children are 14 times more likely to die or be injured from a natural disaster, and climate disasters have been shown to increase gender-based violence including sexual harassment and violence, domestic violence, child marriage, sexual exploitation of children and human trafficking.

Women are often also at the forefront of climate action: becoming environmental defenders, sustainability educators, and helping communities become more resilient to climate change.

International Women’s Day is on Tuesday and the theme is “Gender Equality Today for a Sustainable Tomorrow” with the hashtag #changingclimates.

While some organisations are using #BreaktheBias instead, this is not the official theme but one promoted by a management consultancy, which owns the internationalwomensday.com site and has no connection with the United Nations.

Gillian Triggs, the UNHCR’s Assistant High Commissioner for Protection, said climate change was already displacing large numbers of people across the world.

In sub-Saharan Africa, for example, more frequent and severe cyclones and hurricanes have led to mudslides and the destruction of houses, while loss of grasslands meant that people who herded cattle were moving into more traditional agricultural areas and coming into conflict.

“Unfortunately, women and children are particularly vulnerable in these circumstances and suffer disproportionately,” Dr Triggs told The Sun-Herald and The Sunday Age. “They are enormously vulnerable on the move when they’re displaced – vulnerable to sexual abuse and exploitation of various kinds.”

Dr Triggs, who will be speaking at an online International Women’s Day event run by the UNHCR this week, said the inequality of women – especially in poor countries – meant they had fewer financial resources and were usually unable to get paid work, making it hard to obtain accommodation when they were displaced.

Women in countries with a large amount of climate displacement often worked in agriculture but were unable to use those skills once displaced.

Dr Triggs said improving gender equality would make communities more resilient to climate change, and that women were also often at the forefront of efforts to prevent or adapt to it.

UNHCR’s Assistant High Commissioner for Protection Gillian Triggs (right) holds a focus group discussion with women at the Nanjua B internally displaced persons relocation site in northern Mozambique. Credit: UNHCR/Martim Gray Pereira

When she was in Niger for the UN Refugee Agency, she saw a woman who was a refugee from Mali and also an engineer directing operations for women to construct bricks from cement, sand and water. These can be used to construct small rectangular houses that keep the heat out.

“We do see these really heartening situations in which refugees are helping themselves but where women are very much at the forefront of these efforts to create an environment of self-reliance where they can protect themselves and their families. We see this everywhere,” Dr Triggs said.

Kavita Naidu, an international human rights lawyer and activist from Fiji specialising in climate justice, said climate justice is a feminist issue because the impacts of climate change are not gender neutral.

Speaking at the UN Women’s International Women’s Day event last Friday, she described her work with grassroots women and girls in Asia and the Pacific who have experienced exploitation and violence and some of the worst impacts of climate change.

Ms Naidu said these same women and girls were standing up against their governments, militaries and corporations, to fight for justice and their right to a healthy environment.

“I have never met more powerful and resilient women in my life, who, despite facing these relentless atrocities, have mobilised together to fight for their equality and the right to live in a safe and healthy environment.”

Ms Naidu said she was excited by the Intergovernmental Panel on Climate Change report last week because it emphasised that social justice and equity are critical to urgent climate action.

Renowned naturalist Jane Goodall, who was interviewed by Melbourne academic and climate activist Linh Do in a prerecorded video for the UN Women event, said the media needed to show more stories of hope and highlight that scientific solutions to climate change already exist.

Dr Goodall said the outlook would be hopeless if we carry on with business as usual but that this was not inevitable – reaching people with stories that touch the heart was more effective than only appealing to reason or getting angry.

“A lot of emphasis needs to be put on the fact that we actually scientifically have so many solutions to so much of what’s going wrong,” Dr Goodall said.

“The problem here that we face is the big corporations who haven’t changed their mindset and who feel that everything must be to do with the bottom line, who act as though they believe the natural resources of the planet are infinite. They’re not, they’re finite, but the good news is the number of big corporations that are changing.”

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