As the climate is changing, which animals will adjust and survive?

Climate change is manifesting itself with extreme weather such as prolonged drought and heavy rainfall, while temperatures across the globe show a steady uptick. Scientists predict these phenomena will only get more common and their effects worse as time goes by. How will Earth’s ecosystems respond?

“That is the big question and the background for our study,” said biologist John Jackson of Oxford University – previously at the University of Southern Denmark – , who, along with colleagues Christie Le Coeur from the University of Oslo and Owen Jones from University of Southern Denmark, authored a new study, published in eLife.

The authors focused on 157 mammal species from around the world, analysing population fluctuations and comparing them with weather and climate data going back 10 years.

Their work has shown how animal species have dealt with instances of extreme weather: Did their numbers increase or decrease? Did they have more or fewer offspring?

Patterns of survival

“We can see a clear pattern: Animals that live a long time and have few offspring are less vulnerable when extreme weather hits than animals that live for a short time and have many offspring.

“Examples are llamas, long-lived bats and elephants versus mice, possums and rare marsupials such as the woylie,” said Owen Jones.

As a result of the researchers’ analysis, these animals were found to be less affected by extreme weather: African elephant, Siberian tiger, chimpanzee, greater horseshoe bat, llama, vicuna, white rhinoceros, grizzly bear, American bison, klipspringer, Schreibers's bat.

On the other hand, these animals were on the other end of the spectrum, becoming more affected by extreme weather: Azara's grass mouse, olive grass mouse, elegant fat-tailed mouse opossum, Canadian lemming, Tundra vole, Arctic fox, stoat, common shrew, woylie, arctic ground squirrel.

The researchers found that large, long-lived animals were able to adjust to conditions like prolonged drought and were not as vulnerable to climate fluctuations as were small, short-lived animals. They could invest their energy into one offspring, or hold off until better conditions came along.

Not just weather events but other factors affect species’ vulnerability

Whereas small, short-lived rodents are more susceptible to starvation because large parts of their food base may disappear quickly in the event of a prolonged drought, for example. Not having insects, flowers or fruits means their fat reserves will quickly dwindle, posing a risk to their lives.

That said, the populations of these small mammals soon recover when conditions improve, as they produce a lot of offspring at once, unlike large mammals.

“These small mammals react quickly to extreme weather, and it goes both ways. Their vulnerability to extreme weather should therefore not be equated with a risk of extinction,” said John Jackson.

Jackson also points out that an animal species’ ability to withstand climate change should not be the only criterion to assess its vulnerability to extinction.

“Habitat destruction, poaching, pollution and invasive species are factors that threaten many animal species - in many cases even more than climate change,” he underlined.

Extrapolating scenarios based on similar animals

The researchers’ assessment does not only provide information for today but is likely to offer clues to the future.

“We expect climate change to bring more extreme weather in the future. Animals will need to cope with this extreme weather as they always have.

“So, our analysis helps predict how different animal species might respond to future climate change based on their general characteristics – even if we have limited data on their populations,” said Owen Jones.

Take the woylie, for example – a rare Australian marsupial. Despite the lack of information about the species, biologists are able to predict it will respond to extreme weather as would mice, a species that is also small, lives for a short time, and reproduces quickly.

Possible change in entire ecosystems imminent

“In the same way, there are lots of animal species that we don't know very much about, but whose reaction we can now predict,” explained John Jackson.

The scientists behind the study believe that the ability of different animal species to adjust to climate change is dependent on their life strategy, and this can help us predict ecological changes:

Climate change will have an effect on habitat suitability, forcing species to move to new areas because their old living grounds are no longer hospitable. These shifts depend on species’ life strategies and may possibly have enormous effects on ecosystem function.