John Bruno, from the University of North Carolina at Chapel Hill, believes that while there may be isolated cases where reef health seems to correlate with proximity to human populations, a broader view tells a different story. "My general impression is that the global influences seem to have much stronger impact, but I'm really careful not to totally write off local impacts," he says. Bruno and his colleagues recently analyzed various research surveys conducted at more than 2,500 reefs. They found no overall correlation between reef condition and distance from human populations. However, ocean dynamics are so complicated that simple distance may not be a good measure of human impact at many locations, he says. Commercial fishing, for example, can be quite concentrated far from any human settlement.
Bruno and a large team of collaborators are working to develop a computer grid that more accurately estimates human influence at points around the globe, taking into consideration currents, fishing exploitation and other factors. For their part, the Scripps team continues analyzing their massive dataset from the Line Islands, and will return there in 2009. But, if past results are any indicator, the debate is likely to extend well beyond then—as is reef decline.
Mark Schrope, a freelance writer based in Melbourne, Florida, writes extensively on ocean topics.