Nearly 100 fossil species pulled from a flooded cave in the Bahamas reveal a true story of persistence against all odds—at least until the time humans stepped foot on the islands.
The discovery shows how a variety of human activities pose a threat to the future of island biodiversity, with modern human-driven climate change not necessarily the most alarming.
Thirty-nine of the species included in a new study published in the Proceedings of the National Academy of Sciences no longer exist on Great Abaco Island in the Bahamas. Of those, 17 species of birds likely fell victim to changes in climate and rising sea levels around the end of the ice age, about 10,000 years ago. Twenty-two other species of reptiles, birds, and mammals survived those dramatic environmental changes only to vanish when humans first arrived on the island 1,000 years ago.
Exploring why some species were more flexible than others in the face of climate and human-driven changes could alter the way we think about conservation and restoration of species today, says lead author Dave Steadman, ornithology curator at the Florida Museum of Natural History at the University of Florida.
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Scientists fear that activities like habitat alteration and the introduction of invasive species could pose the greatest risk to island species.
“What we see today is just a small snapshot of how species have existed for millions of years,” says lead author Dave Steadman, ornithology curator at the Florida Museum of Natural History at the University of Florida.
“The species that existed on Abaco up until people arrived were survivors. They withstood a variety of environmental changes, but some could not adapt quickly or drastically enough to what happened when people showed up. So, there must be different mechanisms driving these two types of extinctions. What is it about people that so many island species could not adapt to? That’s what we want to find out.”
For species that were lost at the end of the ice age, climate change, habitat change, and rising seas, with resulting smaller islands, may have caused their populations to become too small to remain genetically viable, resulting in inbreeding.
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A January 2015 study found the Caribbean’s first humans depleted species as small as bats on Abaco. The new study shows several other species that endured until human arrival were lost to activities such as hunting and starting wildfires.
The new research shows how quickly humans can drastically alter habitats, says Hayley Singleton, a graduate student and study coauthor. Unlike during the ice age, modern climate change and other human-driven changes often go hand in hand.
“When humans change habitats at a rate that local species cannot keep up with, that can very quickly result in the losses,” she says. “Likewise, even small climate changes can affect migration and significantly impact habitats. So, you can have the perfect storm where climate and human-driven changes are occurring at the same time, like we’re seeing in places around the world today.”
Future research will explore whether there are fundamental genetic differences between the Bahamian species that persisted and those that were lost when humans arrived. In other words, scientists want to know if there’s a genetic basis for adaptability, Steadman says.
“The answer could help us predict what animals will be affected most by a changing climate and humans.”
Source: University of Florida