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Science 25 March 2005:
Vol. 307. no. 5717, pp. 1959 - 1961
DOI: 10.1126/science.1108485
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Reports

Introduced Predators Transform Subarctic Islands from Grassland to Tundra

D. A. Croll,1* J. L. Maron,2 J. A. Estes,1,3 E. M. Danner,1 G. V. Byrd4

Top predators often have powerful direct effects on prey populations, but whether these direct effects propagate to the base of terrestrial food webs is debated. There are few examples of trophic cascades strong enough to alter the abundance and composition of entire plant communities. We show that the introduction of arctic foxes (Alopex lagopus) to the Aleutian archipelago induced strong shifts in plant productivity and community structure via a previously unknown pathway. By preying on seabirds, foxes reduced nutrient transport from ocean to land, affecting soil fertility and transforming grasslands to dwarf shrub/forb-dominated ecosystems.

1 Department of Ecology and Evolutionary Biology, Island Conservation, University of California–Santa Cruz, Santa Cruz, CA 95060, USA.
2 Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
3 U.S. Geological Survey, Western Ecological Research Center, Santa Cruz, CA 95060, USA.
4 U.S. Fish and Wildlife Service, 95 Sterling Highway, Homer, AK 99603, USA.

* To whom correspondence should be addressed. E-mail: croll{at}biology.ucsc.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)