When European explorers arrived in the Caribbean 500 years ago, they not only upended the lives of the indigenous peoples they met, but also changed entire ecosystems. A new study suggests that lizards and snakes that live on some islands may have become extinct by 70 percent. It was not only the colonists who were responsible for this, but also the cats, mice and raccoons they brought with them.
The findings suggest that it's not humans themselves that are causing problems for vulnerable species, but that we're seeing very different effects, depending on how those humans interact with their environment," said Erle Ellis, "I'm a geographer at the University of Maryland at Baltimore County and wasn't involved in this study." He added: "The new findings are crucial for future conservation efforts." ”
Compared to popular animals such as giant pandas, scientists know very little about the lifestyle of lizards, snakes and other reptiles. They know less about the early history of these animals. However, there is a growing recognition that these species play a key role in ecosystems, pollinating plants, spreading seeds, eating small animals such as insects, and being eaten by larger animals themselves, some even changing landscapes by burrowing into the ground.
So Corentin Bochaton, an zooarchaeologist at the Institute of Human History Sciences, traveled to biodiversity hotspots in the Caribbean. He and his colleagues visited 6 previously excavated caves on Guadeloupe, a group of islands under French administration in the eastern Caribbean. After sifting through different layers of mud on the cave floor and carefully studying the results of previous excavations, they collected tens of thousands of bone fragments, some as small as 3 millimeters.
Of the 43,000 fossils unearthed, the researchers identified 16 different types of lizards and snakes. They divided the fossils into four groups: 32000-11000-year-old fossils, 11650-2540-year-old fossils, 2450-458-year-old fossils (this time after the arrival of the island's indigenous people, before the arrival of European explorers), and fossils from 458 to the present.
The team reports today in the journal Science Advances that at least 4 species of snakes and 5 species of lizards lived on an island 11,000 years ago, but none of them are there now. They were eventually replaced by 4 other species of lizards, two of which first appeared around 2,000 years ago and the other two after Europeans. Those new species are likely to come from elsewhere in the Caribbean.
Pochaton and his colleagues then tracked guadeloupe's nearly 40,000-year evolutionary history of snakes and lizards. They found that before the arrival of Christopher Columbus in 1493, at least 13 species of reptiles flourished and spread through at least 76 populations. For thousands of years, neither climate change nor the presence of indigenous peoples was a problem.
But in the 350 years since European settlement, about half of the population has disappeared, and at least 3 species of snakes and 5 species of lizards have gone extinct. Some islands have lost as much as 70% of their reptiles. "These lizards are likely to have been victims of invasive animals that came with Europeans, such as mongooses and cats, or became extinct after their habitats were replaced by sugar cane fields and pastures," the researchers said. Iguanas and 5 other newly arrived lizard species took their place. "This pattern is likely to be repeated on other islands in the Caribbean." ”
It's unclear what these losses mean for the island ecosystem, but the findings are a bit troubling, with Jonathan Losos saying, "I'm an evolutionary ecologist at Washington University in St. Louis and wasn't involved in this new study." That's because he and other scientists have spent most of their careers studying the interaction between ecology and evolution in the reptiles that live in the Caribbean today. "The current situation has only existed for a few centuries, and we have a very biased view, considering the relatively short history of these animals in the region," he explains. ”
"These results also support a growing theory among scientists that biodiversity can continue to coexist with humans when they manage land with sustainable development common among indigenous people," Elris said. ”