A tiny, uninhabited Caribbean island has proved to hold an unexpected cornucopia of biological diversity, according to researchers who returned last week from a two-week expedition there.
Navassa Island, a U.S. territory with an area of only 1.9 square miles, holds at least 800 species of flora and fauna, many of which are found nowhere else in the world, according to a team from the Center for Marine Conservation in Washington, D.C.
The waters around the isolated island "may possess some of the most pristine and healthy coral reefs in the United States, and perhaps in the whole of the Caribbean," said marine biologist Nina Young, a co-leader of the expedition.
Caribbean waters are still sparkling clear in many areas and land masses retain much of their natural beauty, but experts fear that the situation will deteriorate rapidly. With a population of 40 million people on a landmass that, in aggregate, is no larger than Oregon, the islands are becoming tattered around the edges.
Coral reefs have been severely damaged by disease and bleaching throughout much of the Caribbean. Black spiny sea urchins suffered a catastrophic die-off in the 1980s, perhaps foreshadowing the fate of a variety of species threatened by pollution and human encroachment.
Undisturbed for Centuries
Navassa's ecology, in contrast, is probably very similar to the ecology of the whole Caribbean region hundreds of year ago, before humans invaded the area.
Navassa was discovered in 1504 when Christopher Columbus, stranded on Jamaica, sent crew members to Hispaniola by canoe for help. They landed on the island on their way, but quickly departed when they found it had no fresh water.
Mariners largely avoided Navassa for the next 350 years until U.S. sea captain Peter Duncan landed and claimed the island--and its large deposits of guano (bird droppings)--for the United States in 1857. The guano was mined for use as fertilizer until the end of the century, when the island was abandoned to the booby birds.
The U.S. built a lighthouse on Navassa in 1917 when the sea passage between Cuba and Haiti became an important route for ships heading to and from the Panama Canal. The lighthouse was automated in 1929 and the island again became uninhabited.
Today, the main visitors are ham radio operators, who arrive occasionally to broadcast from the territory, which is accorded "country" status by the International Radio Relay League. Those visitors have left their mark on the island, scattering litter at the one landing site and carving their names and call signs into the rocks.
A Massive Coral Reef
Navassa is, essentially, a massive coral reef that has been lifted from the water to form a huge mesa. It has no beaches. Instead, sheer cliffs rise abruptly from the water, climbing 30 to 70 feet above sea level and looking like the White Cliffs of Dover, according to ichthyologist Michael Smith, who led the expedition with Young.
The only access to the island is via a narrow indentation on the leeward side, where a steel-cable ladder hangs down to the ocean. "You bring your boat close to it and jump for the ladder," Smith said. Smith's team, however, was ferried to the island by helicopter from a Coast Guard cruiser anchored offshore.
The limestone surface of the mesa has been eaten away by rainfall, so that "it looks like Swiss cheese, but with hardly any cheese," Smith said. On much of the island, "you jump from rim to rim over the pits," he added, so travel is very slow.
"It's a remarkably small place," he said. "It's quite odd that there are so many species there."
Before visiting the island, the team studied records from visits to Navassa by teams from the Smithsonian Institution and Harvard University in the 1920s and 1930s. Their surveys showed about 150 species on the island, but they studied only plants, birds and reptiles.
Including insects, mosses, lichens and so forth in their tally, the Center for Marine Conservation team found more than 800 species on the land. As many as 250 of those may be found only on Navassa, Smith said. Specimens of each have been brought back for accurate identification.
Island species include a large number of poisonous scorpions, as well as poison wood trees, distant relatives of poison oak and poison sumac. Fortunately, no one was stung by the scorpions, but several expedition members developed severe reactions to the trees.
Most of the species they found were the types one would expect on an island--mosses, lichens, insects, sea birds and goats and rats introduced by humans. Surprisingly, they also found dogs. Unlike goats and rats, which can obtain enough water from plants and other food sources, dogs need a regular source of fresh water, which the island does not have. "It's a complete mystery how they could survive there," Smith said.