Map Projection

Geographic

Map Description

One direct measure of coral stress is the phenomenon of coral bleaching and mortality associated with widespread elevated sea surface temperatures (SSTs) during the last decade (Hoegh-Guldberg 1999). This is frequently associated with warm temperatures and has been widely predicted to increase in the future. Exposure for one month at temperatures 1 or 2 degrees Celsius higher than the mean averages at the warmest time of year is sufficient to cause the corals to bleach. This map shows the distribution of SST anomalies and coral bleaching events, during one of the largest El Niño events of this century, from late 1997 until mid-1998. Although some records of local coral bleaching date back decades, reports of widespread bleaching have been increasing in recent years. The most recent event was not only widespread, but was also more severe in many areas than earlier events. Actual coral death reached 95 percent in some locations. In a few places massive, centuries-old corals have died; in some other places there has now been at least a partial recovery, with loss of only a few corals.