Ecosystems threatened by climate change can collapse faster than those faced with additional stresses such as bad agricultural practices, new research suggests.
The findings shed light on what could happen in the coming decades if global warming continues to put the natural environment under strain.
Researchers have said that while ecosystems can collapse rapidly, they also have the ability to recover quickly if the stresses they face are removed.
In a study published in Nature Sustainability, scientists used computer models to understand variables influencing the collapse of two lake ecosystems and two forest ecosystems.
Simon Willcock, professor of sustainability at Rothamsted Research, an agricultural research centre, said that simulations found that if an ecosystem is already strained, it will reach a “tipping point” and collapse much sooner if an additional stress is imposed on it.
“When it collapses, it will collapse much closer to the present day if there are multiple drivers,” he told The National. “If it's under multiple stresses, it's much more likely to collapse than the same system under one stress.”
Mr Willcock suggested that ecosystems threatened by climate change could reach the point of collapse much sooner if it also suffers land degradation caused by people.
The tipping point could be brought as much as 80 per cent closer to the present day as a result of several pressures, which may include unsustainable land use, agricultural expansion and climate change, including extreme weather.
One ecosystem scientists studied was Easter Island in Chile, home to the Rapa Nui people, where almost complete deforestation is thought to have been a factor in an acute population decline more than 400 years ago.
Climate change is also projected to lead to significant social and economic impacts in the second half of this century, but the researchers behind the latest study believe the effects could begin sooner.
The UN Intergovernmental Panel on Climate Change also suggested the collapse of Amazon rainforest ecosystems could happen by the end of this century, but a study published last year indicated that it was already close to the “tipping point”.
Beyond this, the ecosystems would be unable to recover if hit by extreme weather events such as droughts, and would become a savannah over a period of decades, leading to drying in that part of the world, with global climatic effects.
Mr Willcock, who is also a senior research fellow at Bangor University in the UK, said that it was important to have better monitoring to help scientists understand the “cumulative stress” on ecosystems, which could show, before it became too late, when they were at risk of collapse.
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He pointed to Lake Erhai in western China, which abruptly became eutrophic, when an entire body of water becomes enriched with nutrients and minerals. This caused algal growth that destroyed other life.
“It rapidly changed into a eutrophic state before anyone expected because people were concentrating on the main stress, which they thought was agricultural run-off,” Mr Willcock said.
“Looking just at that main stress, we didn't expect the lake to become eutrophic.”
While ecosystems are increasingly at risk of reaching tipping points beyond which they collapse, Mr Willcock said some had been helped to recover, as evidenced by “forested ecosystems brought back from potentially savannah”.
“A tipping point doesn't have to be a bad change. It's a very quick change,” he said. “If you can harness the same [factors] that cause the collapse, potentially you can have a very quick recovery.
“People are looking into how to trigger these positive tipping points to trigger recovery.”
Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change and Environment, part of the London School of Economics, said it was important to reduce the pressures that the natural environment faces from industrial agriculture and pollution.
“We have heard warnings that we're currently experiencing or about to experience extinction rates that are comparable with other big geological disasters – the sixth great extinction,” he told The National.
“We cannot carry on this way. We are dependent as humans on our ability to obtain natural resources from other organisms.
“If we kill off plant life, insects, fishes, we will have nothing to feed ourselves.”
Mr Ward, who was not involved in the Rothamsted research, said that governments should aim for the target set out by the UN Convention on Biological Diversity of protecting 30 per cent of land and sea.
“We have to create agricultural systems that allow other species to prosper,” he added.
“We waste a huge amount of food in the global food system, so a lack of efficiency is leading us to overuse and over consume natural resources.”
