Researchers from the University of New Hampshire have found that global warming could cause certain animal populations to shrink in size over time, according to a new study published in the journal Science Advances.
The team found that warm-blooded animals have gotten smaller at least two different times in Earth’s history. The most significant change to body size occurred roughly 54 million years ago when global temperatures rose roughly nine degrees Fahrenheit. Though researchers are not sure what caused the spike, they believe it may have been related to large levels of methane released by dead plants and animals that piled up on the seafloor.
The team studied this trend by looking at a series of fossils uncovered from the Bighorn Basin in Wyoming. They found that the hotter climate changed different mammals all across the world. For instance, an early species of compact horse shrunk 14 percent — dropping from 17 pounds to 14.6 — and the earliest known primate evolved to be 4 percent smaller. Though that may not seem like a big change, it is significant because it goes against past research that shows almost all species get bigger over time.
Smaller animals have more skin per pound than bigger animals. This is an important distinction because it allows more heat to escape their bodies and gives them an advantage over larger species in hotter climates. While the team reports that these changes will not affect humans, they do think current global warming trends could greatly impact future mammal populations.
“These results are very significant because they provide another independent test of whether climate drives changes in body size in mammals,” said Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History, who was not part of the study, according to Phys.org. “If we start to see patterns repeat themselves, we can learn from that. And what we learn from these lessons will certainly be important as we think about the possible response of plants and animals to future climate change.”
Scientists are not sure how fast these changes occur, nor do they know when we may begin to witness them in the wild. However, some past studies also have shown a link between high temperatures and smaller mammals. For example, cows shrink in size and give less milk during warm periods. This new research now gives proof that heating and shrinking are connected over the span of millions of years.
“It’s something we need to keep an eye out for,” said lead author Abigail D’Ambrosia, a graduate student at the University of New Hampshire, according to Tech Times. “The question is how fast are we going to see these changes.”