Cambiamenti climatici, gli orsi polari a rischio estinzione entro il 2100

Nel mondo ce ne sono tra i 22mila e i 31mila esemplari, ma l'innalzamento delle temperature potrebbe farli sparire prima della fine del secolo. L'allarme lanciato dal magazine Nature climate change

A polar bear plays on January 4, 2011 at Prague Zoo in the Czech capital. AFP PHOTO / MICHAL CIZEK (Photo credit should read MICHAL CIZEK/AFP via Getty Images)

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Il riscaldamento globale sta mettendo a rischio gli orsi polari

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Se la situazione non migliorerà, questi animali polari saranno quasi estinti entro la fine del secolo

A polar bear is fed with fish at the zoo in Hanover,Â northern Germany, onÂ February 8, 2012.Temperatures plunged to new lows in Europe where last two week-long cold snap has now claimed more than 220 lives and forecasters warned that the big freeze would tighten its grip at the next time. AFP PHOTO / JULIAN STRATENSCHULTE GERMANY OUT (Photo credit should read JULIAN STRATENSCHULTE/DPA/AFP via Getty Images)

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La notizia è stata riportata dal New York Times, che ha citato uno studio pubblicato sul magazine Nature climate change

Polar bear Vicks jumps in the pool of its enclosure at the Blijdorp Zoo, in Rotterdam, on 15 June 2012. AFP PHOTO / ANP / TOUSSAINT KLUITERS *** netherlands out - belgium out *** (Photo credit should read TOUSSAINT KLUITERS/AFP/GettyImages)

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Secondo Peter Molnar, uno degli autori dello studio, se le emissioni continuassero ai livelli 'business as usual' "ci sono poche chance" per gli orsi polari se non nella regione più a Nord dell'Artico

A polar bear cools off in the water pond of his enclosure at the zoo in Karlsruhe, southern Germany on August 18, 2012. AFP PHOTO / ULI DECK GERMANY OUT (Photo credit should read ULI DECK/AFP/GettyImages)

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Anche se gli orsi polari possono digiunare per un periodo prolungato si arriverà a un "punto in cui finiranno la loro energia", aggiunge Molnar

SAN FRANCISCO, CA - NOVEMBER 15: Pike, a 30 year old Polar Bear plays in man made snow at the San Francisco Zoo on November 15, 2012 in San Francisco, California. Two San Francisco Zoo Polar Bears, Pike (30) and Ulu (32)celebrated their birthdays with 10 tons of man made snow and special treats. (Photo by Justin Sullivan/Getty Images)

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"Non solo dovranno digiunare piu' a lungo e dovranno accumulare più energia per farlo, ma avranno maggiori difficoltà ad accumulare l'energia" necessaria per superare i lunghi lassi temporali senza cibo

A polar bear stands in his enclosure at the Tierpark Hagenbeck zoo in Hamburg, northern Germany, on February 9, 2013. Temperatures in the Hanseatic city were around the freezing point. AFP PHOTO / AXEL HEIMKEN GERMANY OUT (Photo credit should read AXEL HEIMKEN/DPA/AFP via Getty Images)

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In tutto il mondo ci sono tra i 22mila e i 31mila esemplari di orso polare

NORTH SPITSBERGEN, NORWAY - JUNE 06: A female polar bear and her two year old cub venture close to a visiting boat over the moving ice flow on June 6, 2012 in Vaigattfjellet, North Spitsbergen, Norway. North Spitsbergen expects a record 39,000 tourists this year as the region has been boosted by the exposure from recent television documentaries and was also the site of a tragedy last year when British teenager Horatio Chapple, 17, was attacked and killed near the Von Postbreen glacier on the island. (David Yarrow/Getty Images)

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Le 19 popolazioni di questa specie si distrubuiscono in tutta la regione artica: dal Polo Nord alle aree settentrionali di Alaska (Stati Uniti), Russia, Isole Svalbard (Norvegia), Groenlandia (Danimarca). Il 60%, però, si trova in Canada.

BERLIN, GERMANY - AUGUST 23: Two-year-old polar bear Wolodja shakes water from his fur while swimming in his enclosure at Tiergarten Berlin zoo on August 23, 2013 in Berlin, Germany. The zoo recently aquired Wolodja from a zoo in Moscow and zoo authorities are hoping he will pair with a female polar bear to impregnate her with a cub. Another polar bear cub, Knut, rose to world fame after he was born at Zoo Berlin zoo and was rejected by his mother. (Photo by Sean Gallup/Getty Images)

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Gli esemplari maschi adulti pesano mediamente dai 350 ai 700 chili e misurano dai 2,4 ai 3 metri di lunghezza

NEW YORK, NY - FEBRUARY 09: A polar bear is seen at the Bronx Zoo after a snow storm on February 9, 2013 in the Bronx borough of New York City. (Photo by James Devaney/WireImage)

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Le femmine, invece, sono grandi circa la metà e pesano tra i 150 e i 250 chili

Two of the three polar bear cubs born in last November, walk in their enclosure at the Moscow Zoo, on March 22, 2012. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP via Getty Images)

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Appena nati, i cuccioli appena pesano circa 1 o 2 chili, meno di un bambino. Ma dopo circa tre mesi arrivano a 20-25 chili

NORTH SPITSBERGEN, NORWAY - JUNE 06: A two year old polar bear cub ventures close to a visiting boat over the moving ice flow on June 6, 2012 in Vaigattfjellet, North Spitsbergen, Norway. North Spitsbergen expects a record 39,000 tourists this year as the region has been boosted by the exposure from recent television documentaries and was also the site of a tragedy last year when British teenager Horatio Chapple, 17, was attacked and killed near the Von Postbreen glacier on the island. (David Yarrow/Getty Images)

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Grandi e pesanti, gli orsi polari sono anche molto agili: sulla terra ferma possono raggiungere la velocità di 40 chilometri orari

Two polar bears play in the water in their enclosure at Moscow's zoo on December 10, 2015. / AFP / VASILY MAXIMOV (Photo credit should read VASILY MAXIMOV/AFP via Getty Images)

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Sono anche degli eccellenti nuotatori

A mother polar bear plays with one of her three cubs born in last November, at the Moscow Zoo, on March 22, 2012. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP via Getty Images)

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La femmina genera solitamente due cuccioli che nascono tra i mesi di novembre e gennaio. I cuccioli restano con la mamma nella tana fino all'arrivo della primavera