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Report: Most polar bears to die out by 2050

Sept. 8, 2007
Staff and wire reports

Two-thirds of the world’s po­lar bears will be killed off by 2050 — and the en­tire popula­t­ion gone from Alas­ka — be­cause of thin­ning sea ice from glob­al warm­ing in the Arc­tic, U.S. gov­ern­ment sci­en­tists fore­cast Fri­day.

Only in the north­ern Ca­na­di­an Arc­tic is­lands and the west coast of Green­land are any of the world’s 16,000 po­lar bears ex­pected to sur­vive through the end of the cen­tu­ry, said the U.S. Ge­o­log­i­cal Sur­vey, which is the sci­en­tif­ic arm of the In­te­ri­or De­part­ment.

A po­lar bear swims at the De­troit Zoo's Arc­tic Ring of Life ex­hib­it. (Cour­te­sy Mark M. Gas­kill, Phoe­nix Com­mu­ni­ca­tions)


USGS pro­jects that po­lar bears dur­ing the next half-cen­tu­ry will dis­ap­pear along the north coasts of Alas­ka and Rus­sia and lose 42 per­cent of the Arc­tic range they need to live in dur­ing sum­mer in the Po­lar Ba­sin when they hunt and breed. A po­lar bear’s life usu­ally lasts about 30 years.

The forecast is the latest of sev­eral stu­dies and re­ports doc­u­ment­ing threats to po­lar bear pop­u­la­tions.

“Pro­jected changes in fu­ture sea ice con­di­tions, if real­ized, will re­sult in loss of ap­prox­i­mately two-thirds of the world’s cur­rent po­lar bear popula­t­ion by the mid 21st cen­tu­ry,” the re­port said.

Po­lar bears de­pend on sea ice as a plat­form for hunt­ing seals, which is their pri­ma­ry food. They rarely catch seals on land or in open wa­ter. Be­cause the gen­er­al de­cline of Arc­tic sea ice ap­pears to be un­der­es­ti­mated, sci­en­tists said their fore­cast of how much po­lar bear popula­t­ions will shrink al­so may be on the low side.

“There is a def­i­nite link be­tween changes in the sea ice and the wel­fare of po­lar bears,” said USGS sci­ent­ist Ste­ven Am­strup, the lead au­thor of the new stud­ies. “As the sea ice goes, so goes the po­lar bear.”

Am­strup said 84 per­cent of the sci­en­tif­ic vari­ables af­fect­ing the po­lar bear’s fate was tied to changes in sea ice.

As of this week, the ex­tent of Arc­tic sea ice had fall­en to 4.75 mil­lion square miles — or 250,000 square miles be­low the pre­vi­ous rec­ord low of 5.05 mil­lion square miles in Sep­tem­ber 2005, ac­cord­ing to the Na­t­ional Snow and Ice Da­ta Cen­ter.

Sci­en­tists do not hold out much hope that the build­up of car­bon di­ox­ide and oth­er in­dus­t­ri­al gas­es blamed for heat­ing the at­mos­phere like a green­house can be turned around in time to help the po­lar bears an­ytime soon.

Po­lar bears have walked the plan­et for at least 40,000 years.

“In spite of any mitiga­t­ion of green­house gas­es, we are go­ing to see the same amount of en­er­gy in the sys­tem for at least 20, 30, 40 years,” Mark My­ers, the USGS di­rec­tor, said. Green­land and Nor­way have the most po­lar bears, while a quar­ter of them live mainly in Alas­ka and trav­el to Can­a­da and Rus­sia. The agen­cy said their range will shrink to no long­er in­clude Alas­ka and oth­er south­ern re­gions.

The find­ings of U.S. and Ca­na­di­an sci­en­tists are based on six months of new stud­ies, dur­ing which the health of three po­lar bear groups and their de­pendency on Arc­tic sea ice were ex­am­ined us­ing “new and tra­di­tion­al mod­els,” My­ers said.


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Homepage photo courtesy U.S. Fish & Wildlife Service


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Two-thirds of the world’s polar bears will be killed off by 2050 — and the entire population gone from Alaska — because of thinning sea ice from global warming in the Arctic, U.S. government scientists forecast Friday. Only in the northern Canadian Arctic islands and the west coast of Greenland are any of the world’s 16,000 polar bears expected to survive through the end of the century, said the U.S. Geological Survey, which is the scientific arm of the Interior Department.