HAMMERHEAD sharks have fled, corals have turned white and giant barnacles are
dead. The overheated water around the Gal谩pagos Islands, caused by El
Ni帽o in the Pacific, is beginning to take a toll of the archipelago鈥檚
unique wildlife, as ecologists predicted
(This Week, 10 January, p 4).
In Brussels last week, a meeting of the Charles Darwin Foundation heard that
the next few weeks will be crucial. Climate experts originally predicted that
the current disruption of Pacific Ocean currents would tail off by May. But it
now looks likely to drag on.
Marine species have been hardest hit so far, faced with waters 5 掳C
warmer than usual for several months. During diving surveys in February, Ken
Collins, a marine biologist from Southampton University, saw many fishes from
warmer regions but no hammerhead sharks, which prefer cooler waters. 鈥淲hat was
startling was the almost total death of large barnacles and the extensive
bleaching of corals in shallow water,鈥� he adds. This happens when the green
algae that live in the tissues of corals become stressed and desert their
hosts.
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Marine iguanas, unique to the Gal谩pagos, are also in trouble because
the seaweeds they feed on have been replaced by inedible species. 鈥淭hey have
been getting thinner and in the past few weeks we have been seeing significant
mortality,鈥� says Robert Bensted-Smith, director of the Charles Darwin Research
Station on the island of Santa Cruz. Most of the islands鈥� seabirds have also
failed to breed, including the endemic blue-footed booby.
Some Gal谩pagos natives are thriving, however. 鈥淓l Ni帽o鈥檚 really
good for the giant tortoises,鈥� says Tom Fritts of the National Museum of Natural
History in Washington DC. Increased rainfall provides them with an abundance of
vegetation to eat. Annual rings laid down in the tortoises鈥� shells reveal growth
spurts corresponding to El Ni帽o years, says Fritts.
