Wednesday, February 08, 2006

GBR bleaching announcements "premature"

Tom Goreau writes:

As I suspected, the HotSpot in the Great Barrier Reef is now cooling, not intensifying or spreading, so the claims made by some that widespread bleaching is imminent were premature. The temperatures reached moderate bleaching conditions only in a small part of the southernmost GBR. As of now there seems to be no major regional bleaching threat to the GBR, although the warm season is not yet over, and it could get hot again in the coming month.

One reason for this mistaken prediction is that although NOAA dedicates a web site to the Goreau-Hayes HotSpot method, they do not cite any of the original publications that showed that such conditions must remain for a month. As a result many people see the maps of areas that are instantaneously at or above the threshold, and do not understand that they must wait for them to remain at that level for a month before saying bleaching is about to happen.

Even though most of the GBR may be lucky this year, the long term temperature trends for sites across the GBR and around the world, documented in the Global Coral Reef Alliance satellite sea surface temperature data base since 1982, are clearly upward, and serious bleaching is likely to recur, if not this year, within a few more years. It is worth noting that the long term monitoring program of the GBR shows that the average live coral cover is steadily declining, and is now only about 20%. A single major bleaching event could kill most of the remaining corals. But it will probably not be this year, unless there is a sharp rise in temperature in the next few weeks.

(see Hot polyps, 31 Jan)

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