In just 50 years’ time, a third of all plant and animal species on our planet could be wiped out due to man-made climate change, US scientists have warned.
The damning new study of humanity’s impact on ecosystems around the world examined recent extinctions due to climate change, along with rates of species movement and various projections of future climatic conditions.
The researchers said their study is probably the first to estimate broad-scale extinction patterns due to the climate crisis by using data from recent climate-related extinctions and from rates of species movements.
The research team, from the University of Arizona used data from 538 species at 581 sites around the globe and focused on species which had been studied at the same place at least 10 years apart.
They found 44 per cent of the 538 species had already gone extinct at one or more of the sites they had earlier inhabited.
They also generated climate data through measurements taken at the time of the earliest survey of each site and at more recent surveys.
“By analysing the change in 19 climatic variables at each site, we could determine which variables drive local extinctions and how much change a population can tolerate without going extinct,” said Cristian Román-Palacios of the department of ecology and evolutionary biology at the University of Arizona.
“We also estimated how quickly populations can move to try and escape rising temperatures.
“When we put all of these pieces of information together for each species, we can come up with detailed estimates of global extinction rates for hundreds of plant and animal species.”
The study identified maximum annual temperatures – the hottest daily highs in summer – as the key variable that best explains whether a population will become extinct.
But the researchers found average yearly temperatures showed smaller changes at sites with local extinction, even though average temperatures are widely used as a proxy for overall climate change.
“This means that using changes in mean annual temperatures to predict extinction from climate change might be positively misleading,” said Professor John Wiens, also of the University of Arizona.
But the new research indicates most species will not be able to disperse quickly enough to avoid extinction, based on their past rates of movement.
Instead, they found many species were able to tolerate some increases in maximum temperatures, but only up to a point.
About 50 per cent of the species had local extinctions if maximum temperatures increased by more than 0.5C, and 95 per cent if temperatures increase by more than 2.9C.
Projections of species loss depend on just how much warmer the local climate will become in the future.
“In a way, it’s a ‘choose your own adventure’,” Professor Wiens said. “If we stick to the Paris Agreement to combat climate change, we may lose fewer than two out of every 10 plant and animal species on Earth by 2070.
“But if humans cause larger temperature increases, we could lose more than a third or even half of all animal and plant species, based on our results.”
The paper’s projections of species loss are similar for plants and animals, but extinctions are projected to be two to four times more common in the tropics than in temperate regions.
“This is a big problem, because the majority of plant and animal species occur in the tropics,” Mr Román-Palacios said.
The study is published in the Proceedings of the National Academy of Sciences.
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