Edition 5, June 2010
Retreating Glaciers Pave Way For Increased Rat Invasions On South Georgia Island
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June 18th, 2010
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| South Georgia Island, Cumberland Bay. Image source |
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Melting glaciers on the sub-Antarctic island of South Georgia are opening the way for rats to invade new areas, where they threaten breeding birds.
AJ Cook and colleagues found that 97% of 103 coastal glaciers on South Georgia have retreated, and they are doing so at an increasing rate, from an average 8 metres a year in the 1950s to 35 metres a year at present. Some have retreated more than 1 km, one more than 4 km.
Brown rats (Rattus norvegicus) are expected to gain access to important breeding colonies of ground- and burrow-nesting birds.
Initially brought to the island on sealing and whaling vessels, rats already occupy 73% of the vegetated area, which covers just 8.6% of South Georgia (3542 km2). They live in tussac and Festuca grasslands.
South Georgia supports 30 million breeding pairs of seabirds, over 3 million fur seals and 100,000 elephant seals.
Rats are the main threat to the birds, eating eggs and the young of burrow-nesting South Georgia diving petrels, Antarctic prions and blue petrels, and ground-nesting songbirds and waterfowl such as the South Georgia pipit and yellow-billed pintail.
The authors call for rat eradication or erection of man-made barriers, with action needed before further ice barriers to rat migration are lost.
References
Cook AJ, Poncet S, Cooper APR, Herbert DJ, Christie D. 2010. Glacier retreat on South Georgia and implications for the spread of rats. Antarctic Science. doi:10.1017/S0954102010000064.