With climate change come earthquakes, flooding, droughts, disruptions in plant growth, and the extinction of large mammals—including horses. At least that’s what happened 50,000 years ago during the last great episode of global warming. And while the extinction of domestic horses is unlikely in this current situation of climate change, rising temperatures could still have significant effects on our horses.

“The major threats of current climate change to domestic horses would be the extreme climate in short time (such as drought, heat, snow, etc.), which need to be carefully monitored and prevented,” said Zhibin Zhang, PhD, a researcher in the Chinese Academy of Sciences Institute of Zoology, in Beijing. “And effects of the current climate warming on natural or biological disasters (which could affect domestic horse breeding and management) need to be further investigated.” 

Like many large mammalian species, horses suffered the effects of the rapid climate change that occurred during the late Pleistocene and early Holocene epochs. While it didn’t cause their total extinction, like it did for mammoths and frigid-zone rhinoceroses, it did lead them to migrate toward the North Pole in Eurasia, Zhang said. One species, the Equus capensis, did finally die out in the late Pleistocene, but the Przewalski’s and domestic horse (Equus caballus), as well as donkeys and onagers, survived.

Once displaced, they became principle prey to humans in these cooler regions—a phenomenon that might have been accentuated by the fact that so many other large mammal species had died out, Zhang said. While hunting further threatened species survival, the horses held out—probably due to their smaller size (which allowed them to live off less food than a mammoth could) and high fertility rates, he added.

“The climate warming would have changed the habitats of horses’ southern boundaries due to increased rainfall,” said Zhang. He said it eliminated some southern populations and pushed others to move north.

Zhang said a closer look at what happened to horses and other large mammals during the last great climate shift could help us better prepare for what could happen during the current one. That’s why he and colleague Xinru Wan, PhD, also of the Chinese Academy of Sciences Institute of Zoology, recently analyzed the effects of the temperature change on these animals 50,000 years ago.

The pair evaluated data on 2,440 radiocarbon-dated fossils or historical remains of large mammals from the late Pleistocene and Holocene epochs; these data are available online for scientists worldwide to access. Then, they compared the specimens’ ages to where they were found to get an overall picture of large mammal movement, proliferation, and reduction over tens of thousands of years.

They found that climate warming was associated with horses moving northward in both western and eastern Eurasia. Rainfall in Asia increased dramatically, with stronger Southeast and Indian monsoons. That altered the steppe habitats horses had thrived in for hundreds of thousands of years. Meanwhile, glaciers in northern Europe (mainly Scandinavia) were melting, leading to newly available grasslands and thereby opening opportunities for horses to survive there.

As such, the horses proved to be adaptable to the changing climate, they said, rather than victims of it. “Despite the effects of climate warming, horses survived to the middle Holocene,” they stated.

It was, however, that movement that led them right into the world of men, where they quickly became hunting targets. “Climate warming was not the key factor in causing the total or massive extinction of wild horses,” Zhang said. “Humans were.”

Excessive horse hunting during this new episode of climate change seems unlikely, Zhang said. However, the ancient horses’ reaction to climate change 50,000 years ago indicates that our modern horses could be affected by the increasing heat.

The study, “Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia,” will appear in an upcoming issue of the Proceedings of the Royal Society B: Biological Sciences