There has been a lot of talk about how global warming might affect coral reefs, and it seems clear that different reefs will be affected differently. It makes sense to concentrate on saving those reefs that can be saved, rather than wasting resources on reefs that are likely to die anyway. But how do you tell which is which? Well that might have got a little bit easier.
Spatial ecologist Joseph Maina of Macquarie University in Sydney, Australia, and his colleagues have performed a global assessment of areas most susceptible to bleaching. They have examined satellite and tidal data to identify where water is getting warmer. They have also looked at factors that might make it possible for coral to cope with temperature increases. This includes things like high, swift tides, cooling currents, existing large temperature variations that existing corals can already cope with. They also considered destructive factors such as run-off from rivers. All of this work has allowed them to generate a map which shows that some reefs have a brighter future than others.
Reunion in the Indian Ocean comes out best. Using a scale where 1 means maximum stress and 0 means minimum stress, Reunion had a score of 0.13. Key Largo in Florida had a very good score of 0.25 for climactic stress, but it has been badly affected by runoff and over-fishing so it’s total stress level is a high 0.80. That means it would be a good candidate for better protection, since its low climactic score means it has a good potential to respond and recover.
The team’s findings seem to imply that the most likely winners are in the Pacific, northern Red Sea, East Africa, the Caribbean, and parts of the Indian Ocean around Sri Lanka, Reunion and Mauritius. Unfortunately South-east Asian reefs appear disproportionately among the potential losers. Lombok has Indonesia’s best scores, but they are only 0.74, which is very high stress.
Some people feel this information will allow conservationists to focus on areas that can be saved. But others are not convinced and point out that it is too hard to tell which corals will bleach in future. For example, John Bruno, a marine ecologist at the University of North Carolina, Chapel Hill, points out that “The Bahamas bleached in 1998 but not in 2003, while the Virgin Islands bleached in 2010 but not before, and that’s just in the Caribbean.”
But at least this map will add to the debate about what can be done to save coral reefs.
You can read more about the research on Science’s website.