Arctic Ecosystems Being Nibbled Away
The Arctic’s fragile ecosystems are threatened by disturbances from petroleum development to ecotourism. New research shows that even small disturbances may permanently damage tundra: for instance, the single pass of a heavy tank-like tracked vehicle can drain an Arctic meadow.
“In the increasingly accessible Arctic, we need to be wary of relatively small and seemingly insignificant disturbances. Some of the most productive landscapes are being slowly ‘nibbled’ away,” says Bruce Forbes of the University of Lapland in Rovaniemi, Finland, who did this work with two coauthors. This is the first circumpolar assessment of how small-scale human disturbances affect Arctic ecosystems.
The Arctic — lands poleward of the tree line — has large populations of wild caribou and domesticated reindeer and provides critical nesting habitat for immense numbers of shore and water birds. The most controversial threat to Arctic ecosystems is oil and natural gas development. The U.S. may pump oil in Alaska’s Arctic National Wildlife Refuge, Canada is likely to extract gas just east of the refuge, and Russian and northern European energy companies are already operating in the Arctic. Other threats to Arctic ecosystems include mining, military activities, heavy reindeer grazing, and recreational activities such as camping, hiking, and off-road vehicle use.
Based on recent existing studies, Forbes and his co-authors evaluated how well Arctic ecosystems recover from human disturbance. The most extreme disturbances completely remove the tundra’s plant layer, and only the smallest, wettest patches recovered on their own within 20-75 years. For instance, dry patches more than three feet across still had bare centers even after 20 years, largely due to wind erosion.
The researchers also found that lasting changes can result from disturbances that leave the plant layer intact. One of the most widespread disturbances in the Arctic is heavy-tracked vehicles; driving them through an area only once during the summer can be enough to cause long-term damage. Dwarf shrubs can die, meadows can drain rapidly and dry out, and the permafrost that most tundra ecosystems depend on can melt. While summer traffic is banned in the North American Arctic, winter traffic can also be damaging if the snow cover is thin.
Similarly, pedestrian trampling can decrease plant biodiversity, for example, favoring willows and rapidly growing grasses over most other plants and can flatten the hummocks and hollows that give geographical diversity — and thus plant diversity — to the landscape.
“A wide range of small disturbances resulted in…reduced species diversity,” say Forbes and his colleagues. “In addition to the more obvious and large-scale effects associated with petroleum development, mining, and military activity, the explosive growth of ecotourism is affecting all sectors of the Arctic. We suggest that serious consideration should also be given to the less visible effects of seemingly benign recreational activities that inevitably accompany tourism development.”
Forbes, B.C., J.J. Ebersole, and B. Strandberg. 2001. Anthropogenic disturbance and patch dynamics in circumpolar arctic ecosystems. Conservation Biology 15(4):954-969.