Sustainable Footprint

Foxes in Northern Henhouse

How Foxes in the Aleutian Henhouse Doomed Islands' Plant Life
By CHARLES PETIT
From New York Times 2005-03-29
Foxes may not graze, but a new scientific study describes how their arrival on Aleutian Islands destroyed rich grasslands and left only sparse tundra. The authors of the report, which appeared in Science last week, say this transformation shows how an entire ecosystem may go into a tailspin if just one new top carnivore shows up.
The inadvertent experiment began in the late 1700's and continued into the early 20th century as fur traders looking to expand their supply released non-native arctic foxes and, in some cases, red foxes on more than 400 Alaskan islands. Some died out, but many populations survived.
The botanical impoverishment that has resulted is the reverse of what usually happens when a new meat-eater comes along.
"Traditionally, the predator eats the grazer; the grazer no longer eats the green stuff; and the habitat gets more green," said Dr. Donald Croll, a professor of biology at the University of California, Santa Cruz, and the lead author of the report.
An example of the more usual routine is in Yellowstone National Park, where returning wolves, preying on sapling-browsing elk and confining the wary survivors to areas where they can see wolves coming, have touched off a resurgence of willow, aspen and other vegetation.
The contrary effect in the Aleutians, once sorted out, has a simple explanation. The grazers on these islands were grass- and seed-eating Aleutian geese, which are smaller cousins of Canada geese. The foxes drove the geese near extinction, which would have been a boon for grasses except that the foxes also feasted on the eggs and hatchlings of puffins, auklets and other ocean-feeding seabirds they found brooding in vast numbers almost everywhere.
Some islands lost almost all birds except for cliff-nesting species. And as ground-nesting birds faded, so did their nutrient-rich excrement, or guano, which had been a natural fertilizer.
The birds and grassy expanses should rebound in coming decades. For several years, Mr. Byrd and others in the refuge have been eradicating foxes with traps set along Aleutian shores in late winter and spring when, with birds away from nesting grounds, the hungry animals forage along the beach for crustaceans and washed-up edibles. Several thousand foxes have been eliminated and 40 islands have been cleared.

The whole story with some questions can be found in the chapter THEMATIC LESSONS: Foxes in Northern Henhouse.

back

top

Sustainable Footprint

Sustainable Footprint
Projectbureau e-linQ
Nieuw Eyckholt 292P
6419 DJ Heerlen
T (045) 574 11 81
E info@e-linq.nl
I www.e-linq.nl