Coral Reefs May Be More Resilient Than Expected

"It appears that coral reefs are very resilient and can bounce back magnificently if subjected to good management practices and 10 years or so of pristine conditions," says Robert van Woesik, one of the authors of a new study showing that reefs off Palau, Micronesia, have recovered surprisingly well from a 1998 "bleaching" event, caused by high sea water temperatures. "The rare piece of good news in the problem of climate change is that good local management practices might aid recovery of coral reefs."

Van Woesik, a professor of biological sciences at Florida Institute of Technology, examined the recovery rates of reefs in Palau during three different periods following the 1998 bleaching -- in late 2001/early 2002, late 2002/early 2003, and late 2004/early 2005. Global climate models suggest that Micronesia is particularly vulnerable to climate change over the next millennia, and will be likely subjected to repeated thermal stress events and water temperatures considerably higher than historical averages.

Using underwater digital video cameras, van Woesik and his team examined the rate of coral recovery at 13 different sites, and found that recovery rates increased over time; notably, sheltered bay areas, which suffered less in 1998, appeared to support recovery of outer-reef, "wave-exposed sites," by providing a supply of coral larvae to the damaged reefs. The researchers also found that recovery rates were significantly higher between 2002 and 2004 than between 2001-2002.

Because Micronesia is at a great distance from large human population centers, van Woesik hypothesizes that the coral recovery rate is directly linked to human environmental factors -- a promising sign for recovery in other regions.

"Factors such as river pollution, sedimentation, and use changes -- such as fishing pressures -- are all controllable factors," says van Woesik. "They're added to global effects of greenhouse gas emissions that affect climate change. The take-home message is that we can accelerate the recovery rate of coral reefs by adapting human behavior and reducing local pressure on reefs; this research provides encouragement and incentive for local management.

"Clearly, action is required at both ends of the political spectrum -- both globally to reduce greenhouse emissions, but also locally to enhance reef resilience," says van Woesik.

Van Woesik's research appears in the April 2007 issue Coral Reefs, the journal of the International Society for Reef Studies. He will next set up research sites in several other locations, including the Great Barrier Reef and Mexico's Yucatan Peninsula.