Hot Spot Areas

Recent research contradicts a long-held belief that marine species are unlikely to become extinct as a consequence of human activities thanks to their vast geographic ranges. Analyses of the geographic ranges of 3235 species from four phyla (reef fish, corals, snails, and lobsters) has revealed that between 7.2% and 53.6% of each taxon have highly restricted ranges, rendering them vulnerable to extinction. Restricted-range species are clustered into centres of endemism, most commonly referred to as 'hotspots'. The 10 richest hotspots cover a negligible area of the world's ocean, and only 16% of the world's coral reefs, but include between 44.8 and 54.2% of these restricted-range species.

Worryingly a lot of these hotspots occur in regions where reefs are being severely affected by people, potentially leading to numerous extinctions. Hence, restricted range species are common in the sea, and widespread reef degradation could lead to a gathering wave of extinctions, just as is happening on land. The actual risk to marine biodiversity could be even worse. Although a low fraction (7%) of corals were found to have restricted ranges this should be treated with caution because species were identified by morphology. Corals and many other marine organisms with similar morphology conceal substantial genetic differences, even across regions without obvious barriers to gene flow. Future studies may therefore reveal much hidden speciation not obvious from the colonies' morphology that could revise the conclusion that coral species are generally widespread. Extinction risk could be greater than suggested by our findings.

Furthermore 80% of these marine biodiversity hotspots are adjacent to known terrestrial centres of biodiversity themsleves threatened by a variety of human activities.