那里有多少只北極熊?

那里有多少只北極熊?

The global polar bear population is currently about 26,000, according to the International Union for Conservation of Nature (IUCN). That's a rough estimate, but scientists have determined with 95% certainty that between 22,000 and 31,000 polar bears exist on Earth today.

根據(jù)國際自然保護聯(lián)盟(IUCN)的數(shù)據(jù)，目前全球北極熊的數(shù)量約為26,000只。這只是一個粗略的估計，但科學家們有95%的把握確定，現(xiàn)在地球上有22000到31000只北極熊。

These polar bears are divided into 19 subpopulations around the Arctic, although not very evenly. Some polar bear populations number fewer than 200 individual bears, while others consist of more than 2,000.

這些北極熊在北極地區(qū)被分為19個亞群，雖然分布并不均勻。一些北極熊的數(shù)量還不到200只，而另一些則超過了2000只。

Polar bears are grouped into 19 subpopulations living around the Arctic. outdoorsman/Shutterstock

Polar bears live in areas that fall under the jurisdiction of five countries: Canada (Labrador, Manitoba, Newfoundland, Northwest Territories, Nunavut, Ontario, Québec, Yukon); Denmark (Greenland); Norway (Svalbard, Jan Mayen); Russia (Yakutiya, Krasnoyarsk, West Siberia, North European Russia); and the U.S. (Alaska).

北極熊生活在五個國家管轄的地區(qū):加拿大(拉布拉多、馬尼托巴、紐芬蘭、西北領地、努納伏特、安大略、魁北克、育空);丹麥(格陵蘭島);挪威(斯瓦爾巴群島、揚馬延);俄羅斯(雅庫蒂亞、克拉斯諾亞爾斯克、西西伯利亞、北歐俄羅斯);和美國(阿拉斯加)。

Here are the 19 subpopulations of polar bears, along with an estimated size and trend for those with sufficient data:

以下是北極熊的19個亞種群，以及那些有足夠數(shù)據(jù)的估計大小和趨勢:

Are polar bears endangered?

北極熊瀕臨滅絕嗎?

A polar bear swims amid sea ice off the northern coast of Ellesmere Island in the Canadian Arctic. Isabel Kendzior/Shutterstock

Polar bears do face potentially existential threats, at least in some places. At the same time, however, a few populations have rebounded in recent decades from overhunting last century, leading some people to argue polar bears are actually thriving throughout their range. The late U.S. Sen. Ted Stevens of Alaska, for one, said in 2008 "there are now three times as many polar bears in the Arctic than there were in the 1970s," a claim that has periodically resurfaced since.

北極熊確實面臨潛在的生存威脅，至少在某些地方是這樣。然而，與此同時，近幾十年來，一些北極熊的數(shù)量已經(jīng)從上個世紀的過度捕獵中反彈，這使得一些人認為，實際上，北極熊在整個活動范圍內(nèi)都在繁衍。已故的阿拉斯加州參議員史蒂文斯曾在2008年表示，“現(xiàn)在北極的北極熊數(shù)量是上世紀70年代的三倍。”自那以后，這一說法周期性地浮出水面。

A polar bear walks across an ice floe in the Svalbard archipelago. (Photo: Chase Dekker/Shutterstock)

If the polar bear population has really grown so much since the 1970s, though, why is there so much concern for the species? Why still classify them as vulnerable or threatened today? For one thing, despite the encouraging rebound of some populations, there is little evidence to suggest polar bears are thriving overall.

然而，如果自20世紀70年代以來北極熊的數(shù)量真的增長了那么多，為什么人們會對這個物種如此關注呢?為什么今天仍然把它們歸類為脆弱的或受到威脅的?一方面，盡管一些北極熊的數(shù)量出現(xiàn)了令人鼓舞的反彈，但幾乎沒有證據(jù)表明北極熊的整體繁榮。

At least four polar bear populations are likely in decline, according to the IUCN Polar Bear Specialist Group (PBSG), but we have too little data to establish trends for another eight populations, and too little to even estimate a population size for four of those. And while their specific status is more muddled than the overall outlook for climate change itself, there is significant evidence to suggest many polar bear populations are in peril.

根據(jù)世界自然保護聯(lián)盟(IUCN)北極熊專家小組(PBSG)的數(shù)據(jù)，至少有四種北極熊的數(shù)量可能在下降，但我們的數(shù)據(jù)太少，無法確定另外八個種群的趨勢，甚至無法估計其中四個種群的數(shù)量。雖然它們的具體狀況比氣候變化本身的整體前景更加混亂，但有重要的證據(jù)表明，許多北極熊數(shù)量處于危險之中。

How is climate change affecting polar bears?

氣候變化如何影響北極熊?

Polar bears rely on sea ice to travel, hunt seals and breed. FloridaStock/Shutterstock

To understand why polar bears are vulnerable to climate change, you have to know what polar bears eat — and how they get it. Polar bears are apex predators and a keystone species in their Arctic habitats, and their favorite food by far is seals. They specifically target ringed and bearded seals due to their high fat content.

要理解為什么北極熊容易受到氣候變化的影響，你必須知道北極熊吃什么——以及它們是怎么吃到的。北極熊是頂級掠食者，也是北極棲息地的關鍵物種，到目前為止，它們最喜歡的食物是海豹。他們專門針對環(huán)紋海豹和髯海豹，因為它們脂肪含量高。

The average yearly minimum of Arctic sea ice is now shrinking by 13.2 percent per decade. Kathryn Hansen/NASA

In 2019, Arctic sea ice tied for its second-lowest extent on record. This decline is bad for several reasons, since Arctic sea ice performs key services for Earth like reflecting solar heat and influencing ocean currents. It's even more directly important for polar bears, since less sea ice can mean fewer chances to catch seals.

2019年，北極海冰面積達到了歷史上的第二低。這種下降有幾個不好的原因，因為北極海冰為地球提供了關鍵服務，比如反射太陽熱量和影響洋流。這對北極熊來說更為直接重要，因為海冰的減少意味著捕獲海豹的機會減少。

The decline of sea ice is forcing many polar bears to burn more energy in search of food. Baranov E./Shutterstock

The effects of climate change vary by location, and sea-ice decline seems to be affecting some bears more than others so far. Western Hudson Bay had roughly 1,200 polar bears in the 1990s, for example, but that has since fallen to about 800, and as Polar Bears International (PBI) notes, trends in their body condition, survival and abundance have been linked to sea-ice conditions. Bears in Southern Hudson Bay have also suffered a 17% decline since 2011-2012, according to PBI, and their body conditions have similarly been linked to a longer ice-free period.

氣候變化的影響因地點的不同而不同，到目前為止，海冰的減少似乎對某些熊的影響要大于其他熊。例如，在20世紀90年代，西哈德遜灣大約有1200只北極熊，但現(xiàn)在已經(jīng)降到了800只左右。而且，正如國際北極熊協(xié)會(PBI)所指出的，它們的身體狀況、生存和數(shù)量的變化趨勢都與海冰狀況有關。根據(jù)PBI的數(shù)據(jù)，自2011-2012年以來，南哈德遜灣的北極熊數(shù)量也減少了17%，它們的身體狀況也同樣與更長的無冰期有關。