Reports of thousands of walrus forming unusual congregations on Alaska’s North Slope appear to confirm again the environmental challenges posed by relatively low fall ice coverage within arctic water.

Walrus need ice from which to dive in the relatively shallow water above the continent shelf; when it’s not there, they must come to land. With their typical foraging method disrupted, they will likely enter winter in poorer condition than is ideal.

The news of huge on-shore walrus gatherings comes shortly after the U.S. Fish and Wildlife Service took another step toward declaring the walrus an endangered or threatened species. The agency said last week that a petition to list the walrus presented a good case that the species could be threatened or endangered by the lack of ice. It opened public comment on the issue.

This is all troublesome news for a variety of reasons. Obviously, these are not ideal conditions for walrus or other ice-dependent marine mammals. The same ice trend also could reduce specific seal and polar bear populations. Whether it’s enough to truly endanger or threaten the survival of these species is debatable. Nevertheless, the federal government already has decided that polar bears, as a species, could be lost if current trends continue.

Reductions in marine mammal populations also could limit the numbers available to supply rural Native communities where the animals are hunted for food and skins.

Lower populations also are more likely to receive greater government protection against potential disruptions from economic developments such as oil drilling. That should lead Alaskans to want to monitor this issue closely.

Still, not all the news is dire. For the second year in a row, the arctic ice coverage is greater than the previous by a substantial margin. The low point came in 2007, when the late September ice extent dropped to 1.65 million square miles. Last year, the minimum ice coverage recovered to 1.74 million square miles. This fall, satellite monitoring indicates that this year’s minimum will settle at about 2 million square miles.

These are rapid, impressive gains that, in the short term, have brought ice coverage almost back to levels similar to those seen early in the decade. However, many scientists warn that the long-term trend is still toward less ice.

Alaskans should be watching these barometers of climate change carefully as the debate rages about what can or should be done.