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A study from the University College of London, England, has detailed how the current rise in global climate puts the Earth’s ecosystems at risk of sudden and catastrophic losses. The findings, published in the journal Nature, outline how worldwide biodiversity could be reduced as a result of ecological disruption caused by changing temperatures and weather systems, and indicates that some of these disruptions may already be underway.
"It's not a slippery slope, but a series of cliff edges, hitting different areas at different times,” said the study's lead author Dr Alex Pigot, from the UCL Centre for Biodiversity & Environment Research, in a statement. "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."
To arrive at their conclusions, Dr Pigot and his team used climate model data from as far back as 1850 all the way to 2005 to examine the historic threats to biodiversity in the USA and South Africa. They then cross-referenced this information with the habitat ranges of 30,652 species of birds, mammals, reptiles, amphibians and fish using 100 x 100 kilometer (62 x 62 miles) square grid cells to determine which grids were likely to see an increase in sustained temperatures for more than five years.
Their climate model projections showed that in most ecosystems across the globe, the next 10 years will see a shift in conditions that pushes many organisms beyond their comfort zone. If unprecedented temperatures are reached by 2100, on average 73 percent of organisms will find their ecological niches transformed beyond recognition. While it’s likely that meeting this threshold could spell extinctions, the researchers highlight that this cannot be assumed.
"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," said first author Dr Christopher Trisos, from the African Climate and Development Initiative, University of Cape Town, and National Socio-Environment Synthesis Center.
The researchers posit that under a high-emissions scenario, a global temperature increase of 4°C by 2100 could see one in in five constituent species in 15 percent of the world’s ecosystems cross this threshold for livable conditions. They predict that these changes could be sufficient to cause irreversible damage to the functioning of the ecosystem. If emissions are reduced and temperatures increase by 2°C or less, this threshold event for one in five keystone species could be seen in just 2 percent or fewer ecosystems across the globe.
While a considerable improvement on 15 percent, the researchers warn that the 2 percent includes our most biodiverse ecosystems, such as coral reefs. They predict this impact will begin to be felt by 2030 for the Earth’s tropical oceans. Their models also indicate that the same effects on biodiversity will be seen in some of the Earth’s largest forest ecosystems by 2050.
"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," said Dr Pigot. "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 behavior, or with the help of human-led conservation efforts."
