Global warming is about to tear big holes in Earth’s delicate web of life, pushing temperatures beyond the tolerance of thousands of animals at once. As some key species disappear, entire ecosystems like coral reefs and forests will collapse, and some will collapse abruptly, starting this decade, a new study in the journal Nature warns.
Many scientists are seeing recent climate-related mass mortalities, including coral bleaching in the Great Barrier Reef and the widespread mortality of seabirds and marine mammals in the northeast Pacific linked to a marine heat wave, as warning signs of an imminent collapse in biodiversity, said the lead author Alex Pigot, a biodiversity researcher at University College London. The new study shows that nowhere on Earth will escape the impacts.
“In the United States, states from southern Texas to Florida, Appalachia and the West Coast are expected to be particularly at risk, with between 20 and 40% of species facing conditions beyond anything they have experienced. before,” Pigot said.
In these regions, many species live in small geographic areas under a narrow range of climatic conditions. As global warming warms their habitat to the point that it is intolerable, many species have nowhere to go. Some will disappear, with a domino effect affecting dozens of other species. If he gets too hot for bumblebees, for example, it affects plant reproduction. If it is too hot for insects and reptiles, it affects the food supply of birds and mammals.
“I hope our predictions are wrong. But more and more, what we see around us are the signs of what is happening,” Pigot said, referring to research showing how global warming is affecting individual species. “I think these studies show that many species are already living very close to their thermal limits. Our results suggest that these losses are likely to involve multiple species almost simultaneously rather than occurring gradually, one species at a time,” he said.
At current rate of warming, abrupt exposure events in tropical oceans will begin before 2030 and spread to rainforests and higher latitudes by 2050. Risks decrease and come more slowly if global warming is capped at less than 3.6 degrees Fahrenheit, in line with the goals of the 2015 Paris climate agreement, the study concludes.
“If we can avoid the worst of the warming, we can buy some extra time,” Pigot said. “Even if we can get a few more decades, that gives us time to work on expanding protected areas or decide to try things like assisted migration and assisted evolution.”
Even an immediate reduction in greenhouse gas emissions does not prevent warming of up to 7 degrees Fahrenheit by the end of the century, because current warming could be amplified by large increases in heat-trapping methane in the Arctic or by changes in clouds. process, he says.
jennifer sunday, a research biologist at McGill University, said the new study shows for the first time when species will face warmer temperatures than they have ever experienced for five consecutive years. And it turns out that a surprising number of animals in various ecosystems will reach these climate thresholds at the same time, which can lead to widespread disruption or collapse of ecosystems, said Sunday, who was not involved in the research. .
“We didn’t know how events would unfold over time. We have a lot of models that compare species ranges today to those at some future date, but we didn’t know when most of the changes were going to happen,” she said. The research also clearly shows that the impacts of global warming on ecosystems could happen very suddenly.
“I think we often and perhaps subconsciously expect climate change to be a gradual process, but it helps illustrate that impacts can be in spurts,” she said. “As we know today, our human adaptive systems are not good at coping with synchronous events,” she said, referring to the global response to the coronavirus pandemic. The results show that some climate impacts could be as sudden and widespread as the pandemic, testing our adaptive management systems.
Species in the tropics and polar regions will be hardest hit
In the study, Pigot’s team assessed the temperature ranges of more than 30,000 terrestrial and marine species…birds, mammals, reptiles, amphibians, fish and other marine animals and plants – to estimate when they will begin to experience unprecedented temperature conditions. Capping global warming at 2.7 degrees Fahrenheit would greatly reduce the risk of ecosystem failure, but allowing global warming to continue unchecked would quickly lead to widespread declines in biodiversity, they found.
Ecological communities in tropical regions near the equator will be hard hit because many species already live there near the upper end of their heat tolerance spectrum. In high latitudes, towards the poles, communities of species will struggle because those areas are warming about twice as fast as the global average, giving them even less time to adapt, he said. he declares.
Pigot said the study shows how the risks from climate change will change from year to year. “The key finding of our study, that exposure to potentially hazardous weather conditions is likely to occur abruptly, has not been detected before.” he said.
Pigot said he sees parallels between the new study and current discussions of the response to the coronavirus pandemic, which seems to heighten public awareness of how nonlinear systems work, changing slowly at first, then dramatically increasing all of a sudden. . The study shows how biodiversity risks are greatly magnified in a nonlinear fashion with warming of 3.6 degrees Fahrenheit or more, he said.
“By the time things get really bad, it will be too late,” he said. “But our results show very clearly that it is not too late to act to delay the risk or even avoid it altogether for several thousand species. By keeping warming below 2 degrees Celsius (3.6 degrees Fahrenheit), we can effectively flatten the curve of the accumulation of climate risks to biodiversity over time.