When humans first arrived on the shores of what is now the Bahamas, they must have been greeted by giant tortoises, crocodiles, waving palms, and hardwoods like myrtle. But all that changed quickly. A new study reports that human arrival dramatically altered the landscape, destroying most of the old forests and driving large reptiles to extinction.
The first settlers of the Caribbean, a Taíno people called Lucayans, arrived from South America and the Antilles. The exact timing of arrival of the settlers on the northernmost of these islands is not yet known. The region has few archaeological records, but some human remains have been found by divers in sinkholes on Great Abaco Island, Bahamas, dating to after 1100 CE.
In addition to human remains, divers found fossils of tortoises, crocodiles, and hardwood trees—all absent from Great Abaco’s ecosystems today. This absence got a team of researchers thinking about ancient ecosystems of the island.
History in Sediments
Scientists dug into Blackwood Sinkhole on Great Abaco Island and brought up sediments that have remained undisturbed for ages. The oxygen-poor environment of the sinkhole preserved organic materials (like bits of vegetation, pollen, and charcoal residues) that can be dated and analyzed to infer the time when they were deposited. The team used sediment cores about 30 meters long, which were able to provide a continuous history of the island for the past 3,000 years.
The data showed that up to about 1,000 years ago, tropical hardwoods like myrtles and palms occupied the island. Around the year 830, the amount of charcoal in the sediment core increased abruptly. “That’s really our signal for people arriving on this island,” said Patricia Fall of the University of North Carolina at Charlotte and lead author of the new study. This date is earlier than what was thought for human arrival on this island. When they arrived, people burned and cleared land for agriculture and hunting.
Within about a hundred years of their arrival, humans not only destroyed the ancient hardwood forests but also radically altered populations of indigenous animals on Great Abaco. They hunted Albury’s tortoise, the island’s largest land herbivore, to extinction and decimated the island’s population of Cuban crocodiles. “This shows how fragile our ecosystems are and how fast we can have an impact on our natural landscape,” said Fall.
The new study was published in March in the Proceedings of the National Academy of Sciences of the United States of America.
With human habitation, pines, mangroves, and grasses took root on the island. This vegetation was more adapted to fire than hardwoods but not nearly as resilient to the intense and severe hurricanes that struck the islands starting around 1500. This reduced resiliency has resonance today, researchers say, with more frequent and intense hurricanes predicted in the coming years. “We may see it is harder for the pine-dominated island ecosystem to come back,” said Fall.
The results of the sinkhole study are far-reaching, say researchers. “What resonated with me was the scale of human modification of the environment,” said Matthew Peros of Bishop’s University in Sherbrooke, Canada, who studies climate change and archaeology and was not involved in the research. People arrived, and there was a quick and massive impact on the environment, he said, contributing evidence of how people have had an enormous and long impact on shaping ecosystems.
Knowledge of humanity’s history of shaping a landscape is useful for environmental management today, Peros added. “We don’t know what the future will hold; this information may give us some clues as to what it’s going to be,” said Peros.
—Lakshmi Supriya ([email protected]), Science Writer