Wildlife declines observed across Arctic.

• Position: EYE ON EARTH

A new international study of Arctic wildlife suggests that climate change and overharvesting are causing many species to dwindle, although populations in some areas are rebounding after years of protection efforts.

The Arctic Species Trend Index, released in March, tracked 965 populations of 306 different species--representing 35 percent of known Arctic vertebrate species--from 1970 through 2004. It found a 26-percent decline in vertebrates across the High Arctic, while species in the predominantly marine Low Arctic increased by an average of 46 percent. The Sub Arctic, the area most accessible to human development, hosts 3 percent fewer species, according to the report commissioned by the Circumpolar Biodiversity Monitoring Program, a scientific network organized by the eight Arctic countries.

Changes in wildlife populations are often due to natural cycles, but the Arctic is also undergoing impacts associated with increased human activity, including unsustainable rates of fishing and hunting, high concentrations of persistent toxic chemicals, and climate-related effects such as warmer average temperatures and reduced sea-ice extent. North American and Eurasian caribou populations, for example, have declined by about a third from their...