Reef deaths are our fault - January 09, 2008
The reasons behind the troubled state of coral reefs are explored by a swathe of new studies. Unsurprisingly they conclude it is all our fault.
One huge study on coral reefs in 13 countries has shown the impact of growing human populations. Monitoring of reef life at 322 sites in the Caribbean found that the number of people living nearby was the main driver of coral death and loss of fish biomass (press release 1).
“It is well acknowledged that coral reefs are declining worldwide but the driving forces remain hotly debated,” says Camilo Mora, of Dalhousie University, Halifax, Canada
Previously the finger has been pointed at other sources including global warming. “In essence, all the factors — climate change, overfishing, agricultural land use — affect the reefs the same amount. And all these factors are related to each other because they are caused by humans,” says Mora (press release 2).
Reuters thinks the study shows that new and larger-scale approaches are needed to save reefs. The paper should appear soon in Proceedings of the Royal Society of London B.
In other reef news, a paper in Nature Geoscience says that the increasing acidity of the oceans due to global warming will be bad not only for coral but for another important part of the reef ecosystem - crustose coralline algae.
As the New York Times points out, these algae secrete calcium carbonate like corals, and act as “mortar to help hold reefs together”. In experiments Ilsa Kuffner of the USGS found increased levels of carbon dioxide “severely inhibited” the growth of the algae.
“Scientists have already shown that coral growth may decrease as the ocean pH declines. This new evidence shows that other essential reef-builders, the crustose coralline algae, may be even more sensitive than the corals,” Kuffner says (press release).
And another study reported in the Washington Post says that pollution is not to blame for reefs dying. This study concluded that although nitrogen from fertilisers is damaging, most of this damage occurs after a reed is already dead or dying. “Pollution has been seen as one of the major culprits in the loss of coral reefs around the world, but our study indicates that it cannot explain the widespread changes we are seeing, which leave climate change and overfishing as the major culprits,” study author Tim McClanahan told the Post.
Strangely, no journal is listed for this study an no-one else seems to have picked up on it.
Those looking for good deeds in a naughty world, though, might care to check out this week’s Nature feature about a so-far quite successful reef protection scheme in Colombia.
Image: US FWS
Comments
In case there is some interest in the actual publications. The first shows that brown algae are not stimulated by either nitrogen or phosphorus. Brown algae are the common algae on many degraded reefs.
The second estimates the rate of reef decay (loss of calcium carbonate) due to the addition of nutrients.
McClanahan, T. R., M. Carreiro-Silva, and M. DiLorenzo. 2007. Effect of nitrogen, phosphorous, and their interaction on coral reef algal succession in Glover’s Reef, Belize. Marine Pollution Bulletin 54:1947-1957.
Carreiro-Silva, M., T. R. McClanahan, and W. E. Kiene. 2005. The role of inorganic nutrients and herbivory in controlling microbioerosion of carbonate substrate. Coral Reefs 24:214-221.
Posted by: Tim McClanahan | January 9, 2008 08:18 PM