杏吧原创

Snow goose invasion points to Arctic thaw

A warming climate has improved the birds' Siberian nesting site, leading to plagues of the birds invading the Washington state town of Stanwood

In February, birders from across Washington state flocked to the town of Stanwood, population 5068, for the area鈥檚 second annual Snow Goose Festival. Set up to boost the local economy, events this year included a pancake breakfast, birdwatching tours, wine tasting and live music from a local bluegrass band.

For festival organiser Laura Byers, the big attraction is the sheer number of geese that come to call at Stanwood 鈥 a number that has skyrocketed in recent years. 鈥淭he fields are white with them,鈥 she says. But the booming population is not universally welcome, and may in fact be a stark warning of trouble brewing elsewhere: global warming.

The invasion has prompted local farmers to declare war on the birds. 鈥淭hey鈥檙e like locusts,鈥 says Ted Oien, whose dairy farm located just 3 kilometres from the festival grounds has been ravaged by thousands of geese. Oien reckons the birds ate $10,000 worth of grass off his fields last winter. 鈥淭hey keep everything mowed down to nothing,鈥 he says. 鈥淚t鈥檚 hard to run a dairy operation when you don鈥檛 have grass to feed your cows.鈥

While the lesser snow goose (Chen caerulescens) is a familiar sight in Washington, the number of birds visiting each winter has doubled to 83,000 in just 10 years. Mike Davison, a biologist with the state鈥檚 Department of Fish and Wildlife, says the culprit is climate change on a distant, windswept island in the Arctic Ocean. 鈥淲hether you call it global warming or a moderation in temperatures in a specific geographic area, it has caused them to be very successful in nesting,鈥 he says.

The subpopulation of snow geese that calls on Stanwood each year breeds exclusively on Wrangel Island off the north-east coast of Siberia. The birds can only breed in large numbers if Wrangel鈥檚 winter snowpack melts early enough, which historically occurred about once every four years. 鈥淣ow they have been getting access consecutively for five years,鈥 says Davison.

According to John Walsh, a climate scientist with the International Arctic Research Center in Fairbanks, Alaska, Wrangel is indeed warming up, especially during the breeding season. Using data collected by NASA satellites, Walsh says there has been an average increase of 2 掳C on Wrangel for the months of March, April and May since 1977.

The figures are consistent with changes in the Arctic as a whole, which has been warming much faster than the global average. 鈥淏ased on what鈥檚 been going on across the sea in Alaska, all signs point to a week or two advance in the spring snowmelt,鈥 says Walsh.

Oien and other local farmers don鈥檛 care what has caused the boom; they just want the geese to stop invading. Despite firing noisemakers called 鈥済oose bombs鈥 and inviting local hunters to bag as many birds as they can, their efforts have barely made a dint in the gathering flocks.

On 18 April, state and federal biologists will hold a public meeting to discuss other options. But if Davison is right, an unexpected consequence of climate change has now come home to roost.