The EconomistOctober 26th 2019 331S
mall boatscriss-cross Black Rock Reef
on their way to nearby seaweed and
pearl farms. Below, the blue lips of giant
clams open and close amid a jungle of mul-
ticoloured coral. At the sound of a distant
detonation—dynamite fishing, although
illegal, is common in the area—a small
shark swims hurriedly away. The reef lies
nestled off the town of Taytay, on the island
of Palawan in the Philippines. Its vivid
blues, pinks and greens are a welcome
sight given how many nearby corals died
because of unusually warm water almost a
decade ago—a blight that is becoming com-
monplace because of global warming.
The outlook for coral is dire. The Inter-
governmental Panel on Climate Change, a
unbody, predicted last month that a rise in
global temperatures of 1.5oC relative to pre-
industrial times would probably kill
70-90% of the world’s coral reefs. Given
that the planet has already warmed by
about 1oC, the countdown for corals has be-
gun. But the diversity of coral species andthe variety of habitats in which they thrive
mean that they will not disappear in a uni-
form way. Understanding why reefs like
Black Rock survive and recover from over-
heating is essential to conservation efforts.
Black Rock lies in the Coral Triangle, 6m
square kilometres of water in the heart of
South-East Asia that is home to perhaps
half of the world’s coral reefs (see map on
next page). The Triangle’s waters teem with
an abundance of life almost unmatched
elsewhere on the planet. More than 130mpeople depend on it for their food and live-
lihood. The reefs support myriad marine
species, and provide a spawning ground
for the largest tuna fishery in the world. Ac-
cording to a study involving the United Na-
tions Environment Programme, economic
benefits from the Coral Triangle were
worth $13.9bn in 2017. Tourism generated
45% of that, and commercial fishing 42%.
The rest came from coastal development,
which reefs help to protect by acting as
buffers against rough seas.
Coral consists of symbiotic communi-
ties of algae and tiny animals called polyps.
The polyps give the coral its structure. This
provides shelter to algae; they in turn gen-
erate sugars on which the polyps feed.
When temperatures rise, the polyps expel
the algae, causing coral to lose its colour
and die—a process known as bleaching.
Temperature is not the only critical vari-
able: corals are also sensitive to factors
such as light levels, dissolved chemicals
and changing currents.
These sensitivities explain why corals
are so vulnerable. In addition to climate
change, local stresses still abound. “It’s not
about managing the reefs, it’s about man-
aging the people,” says Peter Mumby of the
University of Queensland in Australia. In
the Philippines some 40m of them live
within 30km of a coral reef. Overfishing
disrupts reefs’ ecosystems. Coastal con-
struction can lead to the dumping of sedi-Coral in AsiaPolyp apocalypse
TAYTAY
Reefs face a deadly onslaught from pollution, overfishing and climate changeAsia
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