Coral mass bleaching extent 2002

The purpose of this study was to document the extent of bleaching of the 2002 large-scale (2,000 km) bleaching event on the GBR, for comparison against SST and other bleaching events.

Aerial surveys were conducted at a flying height of 160 m over 11 days between 3 March and 20 March 2002 and covered a total of 641 reefs. Data are visually estimated bleaching status of whole reefs. The surveys were conducted soon after the hottest period was over, a compromise between ensuring that bleaching on reefs was advanced but before major mortality had set in. The data allowed comparison of GBR-wide spatial patterns of bleaching between 1998 and 2002. In both events, more inshore than offshore reefs bleached.

In 2002, ~54% of reefs bleached to some extent with 18% strongly bleached (compared with ~42% of reefs bleached to some extent in 1998 with ~18% strongly bleached). These statistics and the fact that nearly twice as many offshore reefs bleached in 2002 compared to 1998 (41 vs. 21%, respectively) makes the 2002 event the worst bleaching event on record for the GBR.