This year’s extreme heat is putting
the world’s coral reefs under such severe stress that scientists fear
widespread die-offs, endangering not only the richest ecosystems in the ocean
but also fisheries that feed millions of people.
From Thailand to Texas, corals are
reacting to the heat stress by bleaching, or shedding their colour and going
into survival mode.
Many have already died, and more
are expected to do so in coming months. Computer forecasts of water temperature
suggest that corals in the Caribbean may undergo drastic bleaching in the next
What is unfolding this year is only
the second known global bleaching of coral reefs. Scientists are holding out
hope that this year will not be as bad, over all, as 1998, the hottest year in
the historical record, when an estimated 16 per cent of the world’s
shallow-water reefs died.
But in some places, including
Thailand, the situation is looking worse than in 1998.
Scientists say the trouble with the
reefs is linked to climate change.
For years they have warned that
corals, highly sensitive to excess heat, would serve as an early indicator of
the ecological distress on the planet caused by the build-up of greenhouse
“I am significantly depressed by the whole
situation,” said Clive Wilkinson, director of the Global Coral Reef Monitoring
Network, an organization in Australia that is tracking this year’s disaster.
According to the National Oceanic
and Atmospheric Administration, the first eight months of 2010 matched 1998 as
the hottest January to August period on record.
High ocean temperatures are taxing
the organisms most sensitive to them, the shallow-water corals that create some
of the world’s most vibrant and colourful seascapes.
Coral reefs occupy a tiny fraction
of the ocean, but they harbour perhaps a quarter of all marine species,
including a profusion of fish.
Often called the rain forests of
the sea, they are the foundation not only of important fishing industries but
also of tourist economies worth billions.
Parts of the northern Caribbean,
including the United States Virgin Islands, saw incipient bleaching this
summer, but the tropical storms and hurricanes moving through the Atlantic have
cooled the water there and may have saved some corals.
Farther south, though, temperatures
are still remarkably high, putting many Caribbean reefs at risk.