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Marine animals across the world and land animals living in tropical climates are being pushed to their physiological limits as they struggle to adapt to rising temperatures sparked by human-caused climate change.  

That’s according to a major global study of 460 cold-blooded animals on land and sea, which compared the temperatures where these animals currently live to the regions they could live based on their tolerance to temperature extremes.

The study, involving scientists from The Australian National University (ANU), found marine animals are living closer to their thermal physiological limits, making them most at risk of widespread displacement. It means they could be forced to abandon their habitats to seek sanctuary in cooler places.

Study co-author, Dr Joanne Bennett from ANU, said it spells bad news for the Aussie marine species that call the iconic Great Barrier Reef home. 

“Marine species are probably more vulnerable to climate change because they’re already living in areas on the borderline of the temperature their bodies can withstand. If the places they call home get even hotter, their bodies won’t be able to cope,” Dr Bennett said.  

“We know that the oceans are heating at a surprisingly rapid rate and that will force marine wildlife to leave their homes in search of cooler pastures.  

“Tropical environments such as the Great Barrier Reef can house a lot of species because they’re rich with resources. Particularly for those reef-reliant creatures, we know they rely on habitat structure to survive. 

“But if species are forced to travel to new depths where it’s colder, that means they’re faced with a new environment and there’s no guarantee they’ll be able to source the food they need to survive.

“But this problem is not confined to Australia. It’s a global issue.”

On land, the researchers found species living in more temperate and polar climates are not living as close to the edge of their physiological thermal thresholds.  

The critically endangered Neglected Nursery Frog, native to Queensland’s tropical rainforests, is among those caught in a housing crisis. 

“These frogs are being forced out of their natural habitats because they can no longer adjust to rising temperatures. They’re being pushed to their physical limits and have no choice but to leave, and with that comes risks,” Dr Bennett said.  

According to Dr Bennett, the reason these animals don’t live in the more stable climates in the tropics is not because they can’t withstand heat, but because they are unable to compete with other animals for food and other resources that are plentiful in these regions. 

“We found that species in temperate environments can deal with higher temperatures than what they generally experience. However, they are probably more susceptible to other climate-related factors such as extreme weather events including drought,” Dr Bennett said. 

“But during periods of drought, these creatures must compete for food and water and these resources become scarce. Unfortunately, this means that some animals might perish if they are not as good at competing for these resources.”  

Dr Bennett said the findings help researchers better understand how sensitive different cold-blooded animal species might be to future temperature changes and as climate-driven disasters become more frequent and severe.  

“This will help scientists predict how the global distribution of species might change as Earth continues to get hotter and as the climate continues to change,” she said.  

This research was led by McGill University and is a collaboration between scientists from Canada, Australia, Spain, Mexico, Portugal, Denmark and South Africa.  

The paper is published in Nature Ecology and Evolution.  

This article was first published by ANU Reporter.