About 25,000 years ago, the Earth was a very different planet. It was deep in the midst of a geological period referred to as the "last glacial maximum," meaning the last time when the planet was so cold that glaciers reached down from the North Pole into North America, Europe, and Asia. With so much water frozen solid, the ocean levels were much lower. And that was good news for a huge population of bats who ruled the considerably larger Caribbean islands of that age. While there are still many bats in the Caribbean today, the population 25,000 years ago was a lot richer and more diverse.
Trinidad bat photo by Laurie Zuckerman
As you can see in this diagram, some of the islands were many times larger than they are at present, and they teemed with many species of bats. The fossil evidence for these bats surrounds the islands, and scientists have long wondered what them off. One theory was human hunting, and another was that the caves these bats loved were inundated with water as sea level rose.
Writing in a new paper published this week in Ecology and Evolution, biologists Liliana M. Dávalos and Amy L. Russell argue that the evidence overwhelmingly points to rising sea levels as the culprit. As the glaciers melted, sea levels rose so rapidly that the island bats couldn't find a new home quickly enough — and so they died out.
Dávalos and Russell note that this dieoff gives us a snapshot of what might happen to wildlife on Earth over the next few centuries as water levels rise rapidly. While we may not be certain how many inches the ocean will rise as the polar regions melt, we can be sure of one thing. Historical evidence demonstrates that sea level rises lead to extinctions. The question is only how bad they will be.
Read the full scientific paper at Ecology and Evolution