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Deer


Spring is arriving earlier and earlier on the northern coastal plain of the Arctic National Wildlife Refuge.

In 1990, by the time migrating caribou of the porcupine herd were ready to feed their calves, their principal forage species had already gone to seed, and they missed the period of maximum plant growth.

The Arctic


hd: pushed to the edge of the earth
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As temperatures increase worldwide, trees are finding suitable conditions for growth and reproduction further northward. The tree line is pushing toward the Arctic Ocean and, as a result, the area of permafrost and tundra available for Arctic plants and animals is steadily shrinking. Given a sufficient migration of the tree line, certain Arctic species may be pushed entirely off the continent.

Unfortunately, this scenario may be realized all too quickly. One way to visualize the potentially devastating loss of tundra under a scenario of warmer temperatures is to map current temperature gradients across the region. Such a map reveals that the tree line is currently located where average July temperatures are close to 11° C. Given 6° C of warming, the tree line can reasonably be expected to shift to regions where average July temperatures are currently 5° C (i.e., where temperatures are 6° C cooler than at present). A southern Arctic limit at the position of the 5° C July isotherm shows an almost complete loss of mainland tundra ecosystems.

Even with the most sophisticated models and computer programs to predict global weather patterns and plant growth, the final message is the same: massive reductions are expected in the land area available for tundra plants and animals, and the changes are expected to occur at a rate that precludes the evolution or adaptation of Arctic species to new conditions. For example, detailed climate models suggest that a doubling of greenhouse gas concentrations and the accompanying temperature increases will lead to a 30% reduction in the tundra available to Arctic species. At current rates of emission from wasteful use of coal, oil, and gas, concentrations are expected to double in the next century.

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