ANCHORAGE, Alaska－Given a choice between giving birth on land or sea ice, Pacific walrus mothers most often choose ice.

Likewise, they prefer sea ice for molting, mating, nursing and resting between dives for food. Trouble is, as the century progresses, there's going to be far less ice around.

How well walruses cope with less sea ice is at the heart of a legal fight over whether walruses should be listed as a threatened species, giving them an added protection against human encroachments.

The US government in 2008 listed polar bears as a threatened species because of diminished sea ice brought on by climate warming. That year the Center for Biological Diversity petitioned to do the same for walruses.

However, the US Fish and Wildlife Service concluded in October 2017 that walruses are adapting and no one has proved that they "need" sea ice.

An Endangered Species Act listing would require the US Fish and Wildlife Service to designate critical habitat for walruses and plan for their recovery. Federal agencies, before issuing permits for development such as offshore drilling, would be required to ensure walruses and their habitat would not be jeopardized.

Inaccessibility protected walruses for decades, but a rapid decline in summer sea ice has made them vulnerable.

In the Chukchi Sea between Alaska and Russia, where Pacific walrus females and juveniles spend their summer, ice could be absent during that season by 2060 or sooner, according to the Fish and Wildlife Service.

Since 1981, an area more than double the size of Texas－1.58 million square kilometers－h(huán)as become unavailable to Arctic marine mammals by summer's end, according to the National Snow and Ice Data Center.

More open water already has meant more ship traffic. Walruses also could find more humans in their habitat with a reversal of US policy on Arctic offshore drilling. Former president Barack Obama withdrew most Arctic waters from lease sales, but President Donald Trump in April 2017 announced he was reversing Obama, a decision being challenged in court. The administration's proposed five-year offshore leasing plan includes sales in the Chukchi Sea.

AP