At risk! One-third of coral reefs face uncertain future

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By Rohan Arthur

Limited to shallow depths of the ocean, corals get nutrition largely through photosynthesis and produce sturdy living skeletons of aragonite called reefs. Important natural buffers against storm surges and coastal erosion, reefs support nearly 25 percent of all living species and at least 500 million people worldwide. More than 6.9 million tonnes of fish are harvested from reefs across the tropics every year.

A severely threatened ecosystem. More than a third of coral species are in danger of extinction. Reefs themselves are likely to change in form and function regardless of management. For example, Caribbean coral reefs succumbed to a suite of human disturbances, and three decades of careful management has had no impact in improving the algal wastelands that now dominate these reefs.

Even small increases in temperature causes a breakdown in a symbiotic relationship essential to the coral, resulting in bleaching, which eventually kills the coral. In 1998, an ocean-warming event killed nearly 90 percent of coral in places like Lakshadweep. Also worrying is the emerging threat of ocean acidification, which results in increasingly brittle coral skeletons and increasingly fragile reef frameworks. Overfishing, coastal erosion and pollution continue to be the biggest regional threats to reef. A growing demand for shark fins, groupers and sea cucumbers has seen a proliferation of a global export industry capable of rapidly driving certain populations to extinction.

Reducing overharvest, keeping sedimentation and pollution levels in check and preventing physical breakage of corals by anchors and ship hulls is a good start. Reefs may have an inherent buffer capacity to withstand disturbance, but some will succumb to global and regional processes regardless of what we do. Therefore, we have to apply a science-based triage for protecting resilient reefs. In India, this requires bridging the huge knowledge gap we have in understanding how our reefs function and what currently threatens them.

Rohan Arthur is a marine biologist with special interest in coral reefs and the effects of human interference and climate change on coastal ecology

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