GLOBAL warming may thwart attempts to eradicate rats from the sub-Antarctic
island of South Georgia. Glaciers are melting so fast that the rodents will move
to new areas before they can be poisoned, with devastating consequences for
native birds.
Sailing ships brought rats to South Georgia more than 200 years ago. Since
then they have invaded two-thirds of the shoreline, which is covered with
tussock grass. When rats move in, they feed on the chicks and eggs of pipits and
burrowing seabirds, wiping them out.
This is producing profound changes in the landscape. 鈥淭he burrowing birds
improve soil quality by aeration and nutrient provision, so you can tell the
rat-infested areas from the unhealthy look of the grass,鈥� says Sally Poncet of
the South Georgia Baseline Environment Survey.
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Poncet and her colleagues are now trying to eradicate the rats to preserve
the island鈥檚 natural habitat. In small-scale trials, they are distributing
poisoned pellets, alongside 鈥済nawsticks鈥� designed to detect rat activity after
the poison has been taken. 鈥淲e have to wait two years before we can tell if the
trial has been successful,鈥� she says.
But it may already be too late to protect the one-third of the coastline that
is still rat-free. South Georgia is criss-crossed by glaciers which reach down
to the sea and act as a barrier to the army of advancing rats. But the region
has warmed by 0.5 掳C during the past century. This has caused many glaciers
to retreat rapidly, giving the rats the opportunity to spread to new areas.
Growing numbers of ships visiting the island may also bring rats to pristine
areas.