When it comes to adapting to climate change, diversity is the mammal’s best defense. That is one of the conclusions of the first study of how mammals in North America adapted to climate change in “deep time” — a period of 56 million years beginning with the Eocene and ending 12,000 years ago with the terminal Pleistocene extinction when mammoths, saber-toothed tigers, giant sloths and most of the other “megafauna” on the continent disappeared.
“Before we can predict how mammals will respond to climate change in the future, we need to understand how they responded to climate change in the past,” said Larisa R. G. DeSantis, the assistant professor of earth and environmental studies at Vanderbilt who directed the study. “It is particularly important to establish a baseline that shows how they adapted before humans came on the scene to complicate the picture.”
The study found that the relative range and distribution of mammalian families remained strikingly consistent throughout major climate changes over the past 56 million years. This period began with an extremely hot climate, with a global temperature about six degrees hotter than today (too hot for ice to survive even at the poles) and gradually cooled down to levels only slightly higher than today. It was followed by a dramatic temperature drop and a similarly abrupt warming and finished off with the Ice Ages that alternated between relatively cold glacial and warm interglacial periods.
“These data clearly show that most families were extremely resilient to climate and environmental change over deep time,” DeSantis said.
Horses were consistently the most widely distributed family from the Eocene to the Pliocene (and remained highly dominant, just not number one, in the Pleistocene). In contrast, families with more restricted ranges maintained lower range areas. Thus, their work demonstrates that mammals maintained similar niches through deep time and is consistent with the idea that family members may inherit their ranges from ancestral species. The idea that niches are conserved over time is a fundamental assumption of models that predict current responses of mammals to climate change.
Edited from Diversity aided mammals’ survival over deep time.