Decli­ne in polar bear popu­la­ti­on in the sou­thern Beau­fort Sea

In Novem­ber U.S and Cana­di­an sci­en­tists published the results of a 10-year stu­dy peri­od focu­sing on the polar bear popu­la­ti­on dyna­mics in the sou­thern Beau­fort Sea. The results are alar­ming: During the peri­od of inves­ti­ga­ti­on from 2001 to 2010 the num­ber of polar bears in this regi­on drop­ped by about 40%.

The Beau­fort Sea is part of the Arc­tic Oce­an and is loca­ted north of Alas­ka and the Cana­di­an ter­ri­to­ries Yukon and Nor­thwest Ter­ri­to­ries. The stu­dy was moti­va­ted by the fact that a spa­ti­al and tem­po­ral decli­ne of sum­mer sea ice in the sou­thern Beau­fort Sea was noti­ced over the years. Ear­lier pro­jec­tions of a decli­ne in polar bear popu­la­ti­on due to the­se unfa­voura­ble ice con­di­ti­ons had alre­a­dy con­tri­bu­ted to the U.S. government’s decis­i­on in 2008 to regard the polar bear as a threa­ten­ed spe­ci­es. Now the results of the pre­sent stu­dy have con­firm­ed the­se ear­lier pro­jec­tions.

Espe­ci­al­ly in the years 2004 to 2006 a low sur­vi­val rate led to a 25-50% decli­ne in polar bear popu­la­ti­on in this regi­on. For very young indi­vi­du­als it was almost impos­si­ble to sur­vi­ve during this peri­od, as out of 80 cubs obser­ved in Alas­ka from 2004 to 2007 only 2 sur­vi­vors could be con­firm­ed. The reason for the low sur­vi­val rate is seen in a limi­t­ed access to seals, the polar bears favo­ri­te prey, cau­sed by the retrea­ting sea ice. In addi­ti­on the seal abun­dance its­elf decreased in the same peri­od. In 2007 the sur­vi­val rate of adults and cubs began to impro­ve again so that the popu­la­ti­on could at least be sta­bi­li­zed with ca. 900 bears towards the end of the sur­vey. Howe­ver, among sub­adults, tho­se who were recent­ly sepa­ra­ted from their mothers, sur­vi­val decli­ned throug­hout the enti­re peri­od.

So, as in 2004 still a suf­fi­ci­ent num­ber of 1600 indi­vi­du­als could be obser­ved, the popu­la­ti­on final­ly drop­ped to only 900 bears in 2010.

Source: Eco­lo­gi­cal Appli­ca­ti­ons

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