The terrestrial index shows an overall decline of 10%, despite increasing in the late 1970s to mid-1980s. The terrestrial index is the only one shown because the marine index that comprises 40% of the ASTI populations is heavily biased by the Eastern Bering Sea populations, and the freshwater index that comprises only 14% of the ASTI populations is not considered robust enough to allow for analysis. The terrestrial index comprises the largest dataset with 46% of the total number of ASTI populations.
The terrestrial index is fairly stable until the early 1990s, after which there is a steady decline, despite an overall dramatic increase in goose populations over the same time period. The overall moderate decline in the terrestrial index is largely a reflection of declines (-28%) in terrestrial High Arctic populations (mostly herbivores, e.g., Caribou, Lemmings), whereas terrestrial Low Arctic populations (e.g., Lesser Snow Geese) have increased by 7% and Sub Arctic populations have declined (-5%) slightly. The increase in the Low Arctic is due, in part, to the strong increase of goose populations. It could also reflect ecological responses to climatic changes whereby species with more southerly distributions have moved north and are now thriving, while the northernmost, typical High Arctic species have nowhere to move to. However, evidence for this is not conclusive and cumulative factors might be involved.
figure-8
For the period 1970-2004 (High Arctic, n=25 species, 73 populations; Low Arctic, n=66 species, 166 populations; Sub Arctic, n=102 species, 204 populations.)
