Are humans a bigger threat than climate change?

A study of fossils and bones in a Bahamian sinkhole revealed that, of the species no longer alive today, 56 percent made it through a dramatic global warming, only to be killed off by humans. 

University of Florida/File
Fossils in a flooded cave reveal the impact of human activities on biodiversity. A recent National Science Foundation grant will allow University of Florida researchers to excavate in more caves, including this one on Crooked Island in the Bahamas.

Seventy-five percent of Americans believe that global warming is a “very” or “somewhat” serious problem, even if they continue to debate whether human activity is to blame. But it turns out that other species may face an even greater threat than climate change: humans themselves.

In 2004, professional research diver Brian Kakuk managed to inspect a Bahaman sinkhole whose layer of toxic water had put off other explorers – but had perfectly preserved fossils of species now extinct on Great Abaco Island. Mr. Kakuk and his colleagues published their findings Monday in the journal Proceedings of the National Academy of Sciences.

The fossils, which included complete skeletons of crocodiles and tortoises, “gave us an unparalleled snapshot of what the Ice Age life would have been like on a Caribbean isle,” the study’s lead author, David Steadman, told the Los Angeles Times.

In a word, it was tough. Dramatic climate changes during the Pleistocene-Holocene transition, roughly 10,000 years ago, condensed the island to just one-tenth of its former size as glaciers melted, seas rose, and the local flora turned tropical. All around the globe, the end of the ice age set off a vast sweep of extinction: that’s when legendary species like wooly mammoths and giant sloths made their exit.

For years, scientists have debated whether that bout of global warming is responsible for the extinctions, or whether mankind also helped, as climate change let us venture out to new territory: crossing the Bering Strait to the Americas, for instance.

But people have only lived in the Bahamas for the last 1,000 years, giving University of Florida researchers an opportunity to compare the sinkhole’s oldest fossils, deposited before the big melt, with post-Ice Age bones, and those of animals that died after humans came to the island.

Scientists hoped that seeing which species made it from one era to the next, then the next – and why they lived or died out – would hold clues about how animals adapted to the changing climate, and then to humans, who altered the environment even more by hunting and clearing land for agriculture.

Of the 95 species studied, 39 are now extinct. Some 44 percent of the extinctions resulted from changes in climate and rising seas: perhaps because smaller populations forced inbreeding, Dr. Steadman suggests. But the majority adapted and were getting along just fine, until humans changed the game: the remaining 56 percent were wiped out in the last 1000 years.

A $375,000 National Science Foundation grant will now help the team determine whether genetic differences played a role helping some animals adjust to homo sapiens better than others.

It’s possible that the answer will help preserve biodiversity, as animals today again face the twin challenges of global warming and human activity, what University of Florida master’s student and co-author Hayley Singleton calls “the perfect storm.” 

“If we’re losing that high of a percentage over a millennium, is anything going to be left by the time we get to the next ice age?” Steadman asked Live Science.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Are humans a bigger threat than climate change?
Read this article in
https://www.csmonitor.com/Science/2015/1020/Are-humans-a-bigger-threat-than-climate-change
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe