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201519Apr11:27

Polar bears weak­ened by pol­lu­tion as well as cli­mate change

Infor­ma­tion
pub­lished 19 April 2015 | mod­i­fied 29 Jan­u­ary 2017
Archived

Threats to polar bearsCli­mate change caus­ing habi­tat loss and reduced food is the main prob­lem for polar bears, but plas­tic waste and other pol­lu­tants are grow­ing risks.

Greenland’s polar bears have a thy­roid prob­lem. Their endocrine sys­tems, too, are being dis­rupted. In both cases the cul­prit agency is envi­ron­men­tal pol­lu­tion by a range of long-​lived indus­trial chem­i­cals and pesticides.

Kristin Møller Gabrielsen of the Nor­we­gian Uni­ver­sity of Sci­ence and Tech­nol­ogy in Trond­heim and col­leagues report in the jour­nal Envi­ron­men­tal Research that they exam­ined the liver, mus­cle and kid­ney tis­sues taken from seven polar bears killed by Inuit hunters in East Green­land in 2011 and analysed the effect of more than 50 con­t­a­m­i­nants in plasma sam­ples from these polar bears (Ursus mar­itimus), to see what effect organohalo­gen com­pounds could have on the bears’ thy­roid systems.

All mam­mals have thy­roid sys­tems, and these are phys­i­o­log­i­cally essen­tial for growth, devel­op­ment, repro­duc­tion, stress response, tis­sue repair, metab­o­lism and ther­moreg­u­la­tion (an animal’s abil­ity to keep its body tem­per­a­ture within lim­its): dis­rup­tion at any stage of life can be dam­ag­ing, but thy­roid reg­u­la­tion is vital in the ear­lier stages of life.

But the researchers found high con­cen­tra­tions of plas­tic pol­lu­tion and pes­ti­cide con­t­a­m­i­na­tion in the crea­tures’ tis­sues, many of which could affect the hor­monal systems.

Retreat­ing ice
Polar bears face an uncer­tain future: the Arctic’s most iconic preda­tor depends on sea ice for access to the most nour­ish­ing prey — seals − but thanks to global warm­ing dri­ven by green­house gases dis­charged by humankind since the start of the Indus­trial Rev­o­lu­tion, the ice is in retreat. This is a threat, espe­cially, in the spring when polar bears gain most of their annual fat reserves by con­sum­ing seal pups before com­ing ashore for the sum­mer. The bears can and do for­age on land for small prey, eggs, berries and so on. Research con­ducted at Spits­ber­gen showed such type of for­ag­ing devel­op­ment in polar bears. This video shows suc­ces­sive vis­its by polar bears to a bar­na­cle goose colony, west coast of Spits­ber­gen, Sval­bard. Bears walk from nest to nest to eat the eggs, leav­ing behind the upset nest own­ers. Other bird species that are pre­dated on this video are eider and glau­cous gull. The video sum­marises 20 hours of polar bears feed­ing in the colony through­out the 2012 breed­ing season:


(Video: Youtube; Author: Jouke Prop; The video speed is 5x nor­mal. The field work was by Jouke Prop, Eva Wolters, Tom van Spanje, Oebele Dijk and Thomas Oudman.)

But new research sug­gests that this is unlikely to help them much.

The health of the Arc­tic polar bear is being attacked from all fronts, but among many other fac­tors is the expo­sure to envi­ron­men­tal con­t­a­m­i­nants,” said Maria Jesus Obre­gon, of the Bio­med­ical Research Insti­tute in Madrid, one of the authors.

A wide vari­ety of organochlo­rine com­pounds and pes­ti­cides have an effect on the thy­roid hor­mones in plasma, tis­sues and deio­d­i­nase enzymes, which are in charge of sta­bil­is­ing the thy­roid hor­mones in tissues.”

The biggest prob­lem that con­fronts the polar bear is still cli­mate change, loss of habi­tat and a more pre­car­i­ous food sup­ply. But as a marine mam­mal, the bear is exposed to a huge range of pol­lu­tants deliv­ered by mod­ern indus­try, trans­port and commerce.

Polar bears are listed as a threat­ened species under the United States Endan­gered Species Act and are clas­si­fied as “Vul­ner­a­ble” with declin­ing pop­u­la­tions on the IUCN Red List of Threat­ened Species™.

Con­ser­va­tion guide­lines
Researchers in Feb­ru­ary cal­cu­lated that in 2010, around eight mil­lion tons of plas­tic waste ended up in the world’s oceans.

A sec­ond team of researchers has framed guide­lines for the con­ser­va­tion of the polar bear, and pro­posed 15 mea­sures that could deter­mine the fac­tors impor­tant in sav­ing the crea­ture from ulti­mate extinction.

They report in the jour­nal Sci­ence of the Total Envi­ron­ment that they ques­tioned 13 spe­cial­ists from four nations to pro­pose ways of mea­sur­ing polar bear health. Not sur­pris­ingly, cli­mate change topped the list of threats, but the list also included nutri­tional stress, chronic phys­i­o­log­i­cal stress, dis­eases and par­a­sites, and increas­ing expo­sure to com­peti­tors. Expo­sure to con­t­a­m­i­nants was the third largest threat.

We still don’t know to what extent envi­ron­men­tal changes will affect polar bear health and there­fore its con­ser­va­tion,” say the authors.



(Source: Cli­mate News Net­work arti­cle by Tim Brad­ford, 17.04.2015)


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