Richard Musgrove
Dr Richard Musgrove is a zoologist and science journalist. He writes for Cosmos and Double Helix.
By Richard Musgrove
Scientists will be able to better identify which amphibian species will be most impacted by climate change, thanks to a new study by UNSW researchers.
Amphibians, including frogs, toads, salamanders and newts, are the world’s most at-risk vertebrates, with more than 40% of species facing anthropogenic threats. [IM1] [RM2]
Ectothermy, also referred to as ‘cold bloodedness,’ makes these creatures particularly vulnerable to global heating — their body temperatures follow those of their environments, which means all their metabolic processes are tied to temperature. Global heating also impacts the quality and quantity of their ecosystem’s water, used for everything from breathing to breeding.
It’s important to work out which species will be heat tolerant, and which will not, as the planet passes 1.5oC of global heating above preindustrial levels.[IM3]
Researchers at the University of New South Wales have worked that out for 60% of the world’s amphibian species. [IM4]
Quantifying the resilience of biodiversity to a changing climate is one of the most pressing challenges for contemporary science, says lead author, Dr Patrice Pottier
The researchers selected previously published heat tolerance data on 524 amphibians known to be either aquatic or semi-aquatic or burrowers, ground or tree dwellers.
“We wanted to better understand the risk climate change poses to amphibians and so put together the most comprehensive compilation of heat tolerance limits to date,” Pottier says.
The data generated further information on 5203 species through data imputation – a statistical method that fills in missing information using patterns from existing data, he says.
“In this case, it predicts heat tolerance limits for species we do not have data for by looking at how heat tolerance is linked to factors like habitat type, environmental temperature, and evolutionary history.”
Estimates were made of the body temperatures these species might experience within each microhabitat.
“We assumed a best-case scenario, where they stay in the shade and keep their skin wet, which could help them survive extreme heat,” says Pottier.
They then compared daily environmental temperature patterns to heat tolerance limits and projected how often those limits could be exceeded under different projected global warming scenarios (current, +2°C, +4°C) across their geographic ranges.
One hundred and four (2%) of the 5203 species are already exposed to overheating when in the shade, says Pottier, this rises to 390 species (7.5 %) at 4oC global heating.
Overheating risk is often based on how close a population is to the equator, however this study suggests a more nuanced outcome. “It has previously been often assumed that species closer to the equator are at greater risk from overheating due to climate change than those in temperate regions,” says Pottier.
Read more: Amphibian adaptation to climate change
“However, our study found that tropical species in the Southern Hemisphere are the most impacted by overheating events, while non-tropical species are more impacted in the Northern Hemisphere.”
“Assuming that all tropical species are more vulnerable than temperate species can be misleading,” says Pottier. Extremes are relative to heat tolerance, he says.
The researchers found that species were more affected at high global heating levels, with impacts proportionally greater under +4C of warming than between current levels and +2oC
“This shows that going above +2C of global warming can be a tipping point where we may see a lot of local extinctions,” says Pottier.
Amphibians are both predators and prey, which means that such extinctions can have extensive knock-on effects throughout ecosystems, he says
“We used very conservative estimates in this study assuming access to cool shaded environments. Therefore, the impacts of global warming will likely exceed our projections. So, all efforts to limit global warming are needed to protect the world’s amphibians.”
The paper is published in Nature.
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