Fossils give clues about how turtles might respond to a warming planet

The distribution of ancient tortoises from when the planet was warmer than it is today is helping scientists anticipate how living tortoises may respond to environmental change.

future predictions of global warming It means that current tortoise habitats are likely to become unsuitable, but new areas could become available if the tortoises can adapt in time.

With global temperatures projected to exceed 1.5°C above pre-industrial levels in the coming decades, environmental change It is expected to have a devastating effect on animals and plants around the world. However, determining how different species will be affected is difficult to anticipate.

A new study published in current biology analyzes the distribution of terrestrial fossils and freshwater turtles over the past 100 million years during periods when temperatures were much warmer than they are today. The researchers then used this information to project and predict how modern tortoises may respond to future climate scenarios.

Professor Paul Barrett, a paleobiologist at the Museum and lead author of the study, says: “What we found is that many of the areas where tortoises are particularly diverse right now will become drier and warmer due to human-caused global warming.” . as a result, those areas will become less suitable for these animals to live there.”

“On the other hand, as the world warms, other places may become habitable for turtles that previously would not have been suitable. They could then migrate to different areas, but that depends on whether they can do it in time, unhindered by human interference. “

Can we predict how turtles will respond to environmental change?

Turtles are a group of reptiles found on every continent except Antarctica. include sea ​​turtlesterrapins and tortoises and are made up of species that live on land and in salt and fresh water.

As cold-blooded animals, tortoises cannot generate their own heat and are therefore dependent on their environment to regulate body temperature. Therefore, its distribution and diversity of species is closely linked to environmental conditions.

Previous research has looked at the distribution of fossil tortoises and compared them to climate models from those time periods. The study revealed that the conditions of the areas occupied by ancient tortoises were similar to those of living species.

“Our latest research goes one step further,” explains Paul. “We wanted to know what would happen to the distribution of turtles on worlds that are warmer than today.”

“We looked at two time periods over the last 100 million years during the warmest parts of the Cretaceous and the Eocene. We then took that information and projected forward to a world that is 1.5°C warmer than now, which is foresees that it will happen in the next decades”.

“Since turtles have not changed much in their ecology over the last hundred million years, we can assume that environmental conditions that affected its distribution today were also restrictions on its distribution in the past.”

Turtles have a surprisingly good fossil record compared to many other organisms because their shells are relatively well preserved. This gives scientists a good idea of ​​what their distribution would have been like in the past.

Dr. Alfio Alessandro Chiarenza, a researcher at the University of Vigo and lead author of the study, says: “Turtles are extraordinary biological models for understanding the biogeography of living animals due to their long evolutionary history, which probably predates the dinosaurs. “. “

“This means that they faced and survived a lot of environmental changes. So we wondered if that might also tell us something relevant to their conservation in the wake of ongoing anthropogenic climate change.”

How will turtles respond to climate change?

Turtles are hardy animals, having been around for 230 million years and withstood many mass extinctions, including the one that killed off the dinosaurs. But their future is threatened once again when humans radically alter the environment.

“By looking at the modern and fossil distribution of tortoises and reconstructing their ideal climatic conditions, we found that in the past, tortoises moved poleward in times of global warming,” Alfie says. “If we project the ideal conditions where turtles could live with future emission scenarios, by 2100 we expect these animals to reach similar high latitudes.”

“Unfortunately, the rate at which this change is occurring might be too fast for evolutionary timescales. Also, many of these high-latitude areas correspond to the densely human-populated temperate zones, so our own distribution and pressure in these areas it can increase even more.” hinder their survival.

“By looking at deep time history and merging modern biological knowledge with paleontology, we can provide additional guidance in the conservation of this group of reptiles.”

This story is republished courtesy of the Natural History Museum. Read the original story here