The researchers believe there could be severe ecological disruption in the coming decades, and the first waves could already be happening.
According to lead author Dr Alex Pigot: “We found that climate change risks to biodiversity don’t increase gradually. Instead, as the climate warms, within a certain area most species will be able to cope for a while, before crossing a temperature threshold, when a large proportion of the species will suddenly face conditions they’ve never experienced before.”
“It’s not a slippery slope, but a series of cliff edges, hitting different areas at different times.”
Climate model data from 1850 to 2005 was used and cross-referenced with the geographic ranges of 30,652 species of birds, mammals, reptiles, amphibians, fish, and other animals and plants. The data was available for areas across the globe, divided up into 100 by 100km square grid cells.
They used climate model projections for each year up to 2100 to predict when species in each grid cell will begin experiencing temperatures that are consistently higher than the organism has previously experienced across its geographic range, for a period of at least five years.
“The historic temperature models, combined with species ranges, showed us the range of conditions that each organism can survive under, as far as we know,” said first author Dr Christopher Trisos. “Once temperatures in a given area rise to levels that the species have never experienced, we would expect there to be extinctions, but not necessarily – we simply have no evidence of the ability of these species to persist after this point.”
Ecological concerns have taken a backseat in recent months as governments around the world battle to contain the coronavirus pandemic. One of the adverse effects of the virus has been a marked reduction in greenhouse gas emissions due to reduced economic activity around the globe.
However, this is expected to bounce back strongly once the worst of the pandemic is over and lockdowns cease.
Campaigners had hoped that a series of landmark summits would turn 2020 into a pivotal year for global action on climate change. However, plans to hold a major wildlife summit in China in October and a UN climate summit in Scotland in November have been pushed back to 2021.
The researchers said that on average, 73 per cent of the species facing unprecedented temperatures before 2100 will cross that threshold simultaneously.
They predict that if global temperatures rise by 4°C by 2100, under a “high emissions” scenario which the researchers say is plausible, at least 15 per cent of communities across the globe, and potentially many more, will undergo an abrupt exposure event where more than one in five of their constituent species crosses the threshold beyond their niche limit within the same decade. Such an event could cause irreversible damage to the functioning of the ecosystem.
However, if warming is kept to 2°C or less, potentially fewer than 2 per cent of communities will face such exposure events, although the researchers caution that within that 2 per cent includes some of the most biodiverse communities on the planet, such as coral reefs.
Dr Pigot said: “Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction.”
“Keeping global warming below 2°C effectively ‘flattens the curve’ of how this risk to biodiversity will accumulate over the century, providing more time for species and ecosystems to adapt to the changing climate – whether that’s by finding new habitats, changing their behaviour, or with the help of human-led conservation efforts.”