Researchers suggest that global warming might be causing mammals to shrink. They discovered evidence that mammal populations have “dwarfed” at least twice throughout time when temperatures became too high.
Global warming has great impacts on the ecosystem. While looking at the changes which occurred during Earth’s history, researchers discovered evidence that mammals had shrunk during the Paleocene-Eocene Thermal Maximum (PETM). This was the largest global warming event ever recorded. However, they remain skeptical about the impact that other warming events could have on mammals.
Abigail Carroll, a researcher from the University of New Hampshire, declared that, during PETM, large quantities of carbon dioxide were released into the atmosphere. Now, the quantities of CO2 pumped into the atmosphere are almost ten times bigger than they were during PETM. This might lead to terrible consequences on mammals and the environment.
Teeth, a size indicative
To find the answers she needed, Carroll started a study she published in the journal Science Advances. She and her colleagues wanted to find out if dwarfing events among mammals could be caused during other warming periods.
They looked at the tooth enamel in several fossils from a smaller warming period. The teeth could provide information about the size of the mammals at the time and if they underwent dwarfing. Two of the mammals, an early horse (Arenahippus pernix), and an artiodactyl the size of a rabbit (Diacodexis metsiacus) decreased in size by 14 percent during the event. This confirmed that dwarfing could, indeed, occur during other warming periods.
Why does dwarfing occur?
There are several hypotheses on this peculiar event. One of them is related to the fact that smaller animals live closer to the equator because it is easier for them to cool off. On the other hand, larger animals live closer to the poles, because they are better equipped to face the cold. Thus, dwarfing could be a product of evolution and an adaptive response to warmer temperatures.
The second hypothesis suggests that the higher concentration of CO2 in the atmosphere decreased the nutrient concentration in plants, so mammals had to shrink. Carroll declared that she would opt for a combination between these two hypotheses.
“I lean towards a theory that combines a bit of both explanations. I think it is possible that there were many droughts, which decreased the amount of nutrients available for plants and this then had an impact on the rest of the food chain.”
Nowadays, global warming might have a similar impact to mammals. Researchers have already observed that dwarfing started affecting some mammal species, such as the woodrat. Unfortunately, we have to wait and see what other consequences climate change might have on the environment.
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