When Bernhard Riegl began surveying coral reefs off the Puerto Rican island of Vieques a few years ago, he was prepared for the worst. For nearly 60 years, the U.S. Navy had used the island as a live-fire training ground for bomber pilots, naval gunners, and assault troops, who battered the area with tons of explosives. So the marine biologist wasn't surprised when, on dives, he saw "shrapnel scattered around, this crater right in the reef, and a bomb sticking out of some coral."
But things weren't as bad as they seemed, Riegl and his colleagues report in the current issue of the Journal of Coastal Research. Surveys show that the reefs around Vieques are actually in slightly better shape than corals protected by nearby marine parks. "It wasn't quite what some people expected," says Riegl, a researcher at Nova Southeastern University in Dania, Florida.
That doesn't mean that the Vieques reefs have had it easy. As at other Caribbean islands, disease and hurricanes appear to have devastated reefs in the island's shallower waters. But overall, such natural disturbances appear to have done more damage than past military activity, the study concludes. "Germs and storms, rather than bombs ... seem to have taken the worst toll," the authors write.
Riegl's team compared 24 coral plots at Vieques with six sites at the nearby island of St. Croix, where marine parks protect some reefs. Comparing features such as coral abundance and diversity, they found "surprisingly little differentiation" between the two islands--although some Vieques reefs were slightly more abundant. They also found few differences between sites squarely within the Vieques bombing range and those outside of it--although Riegl says it is clear that in a few places reefs were pulverized by explosions.
Ironically enough, the bombings might actually have helped protect the reefs, because the Navy closed much of the island to residential and tourist development during its occupation, says Riegl. And after the Navy left in 2003, much of the free-fire zone was turned into a wildlife refuge. As a result, Vieques avoided the polluted runoff and sediment from land-based development that have seriously damaged reefs elsewhere in the Caribbean.
"The take-home message seems to be that the most glaring problems--like bombing--might not be as serious in the long term as the quiet or silent problems, like runoff and development," says David Niebuhr, a marine biologist who has done fieldwork at Vieques and now runs education programs at the Mote Marine Laboratory in Sarasota, Florida.
That's true, but the new study may paint too bright a picture, says Edwin Hernández-Delgado, a marine biologist at the University of Puerto Rico, Río Piedras. He says other researchers have found that corals are less common in heavily bombed parts of the range and that nobody knows how thousands of unexploded shells may affect marine life. "These are major issues that need to be addressed" by scientists, he says, if they want to get "a more complete picture of long-term, sustained impacts of military operations."