那里有多少只北极熊?

那里有多少只北极熊?

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.

根据国际自然保护联盟(IUCN)的数据，目前全球北极熊的数量约为26,000只。这只是一个粗略的估计，但科学家们有95%的把握确定，现在地球上有22000到31000只北极熊。

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.

这些北极熊在北极地区被分为19个亚群，虽然分布并不均匀。一些北极熊的数量还不到200只，而另一些则超过了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).

北极熊生活在五个国家管辖的地区:加拿大(拉布拉多、马尼托巴、纽芬兰、西北领地、努纳伏特、安大略、魁北克、育空);丹麦(格陵兰岛);挪威(斯瓦尔巴群岛、扬马延);俄罗斯(雅库蒂亚、克拉斯诺亚尔斯克、西西伯利亚、北欧俄罗斯);和美国(阿拉斯加)。

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

以下是北极熊的19个亚种群，以及那些有足够数据的估计大小和趋势:

Are polar bears endangered?

北极熊濒临灭绝吗?

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.

北极熊确实面临潜在的生存威胁，至少在某些地方是这样。然而，与此同时，近几十年来，一些北极熊的数量已经从上个世纪的过度捕猎中反弹，这使得一些人认为，实际上，北极熊在整个活动范围内都在繁衍。已故的阿拉斯加州参议员史蒂文斯曾在2008年表示，“现在北极的北极熊数量是上世纪70年代的三倍。”自那以后，这一说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世纪70年代以来北极熊的数量真的增长了那么多，为什么人们会对这个物种如此关注呢?为什么今天仍然把它们归类为脆弱的或受到威胁的?一方面，尽管一些北极熊的数量出现了令人鼓舞的反弹，但几乎没有证据表明北极熊的整体繁荣。

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.

根据世界自然保护联盟(IUCN)北极熊专家小组(PBSG)的数据，至少有四种北极熊的数量可能在下降，但我们的数据太少，无法确定另外八个种群的趋势，甚至无法估计其中四个种群的数量。虽然它们的具体状况比气候变化本身的整体前景更加混乱，但有重要的证据表明，许多北极熊数量处于危险之中。

How is climate change affecting polar bears?

气候变化如何影响北极熊?

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.

要理解为什么北极熊容易受到气候变化的影响，你必须知道北极熊吃什么——以及它们是怎么吃到的。北极熊是顶级掠食者，也是北极栖息地的关键物种，到目前为止，它们最喜欢的食物是海豹。他们专门针对环纹海豹和髯海豹，因为它们脂肪含量高。

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，北极海冰面积达到了历史上的第二低。这种下降有几个不好的原因，因为北极海冰为地球提供了关键服务，比如反射太阳热量和影响洋流。这对北极熊来说更为直接重要，因为海冰的减少意味着捕获海豹的机会减少。

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.

气候变化的影响因地点的不同而不同，到目前为止，海冰的减少似乎对某些熊的影响要大于其他熊。例如，在20世纪90年代，西哈德逊湾大约有1200只北极熊，但现在已经降到了800只左右。而且，正如国际北极熊协会(PBI)所指出的，它们的身体状况、生存和数量的变化趋势都与海冰状况有关。根据PBI的数据，自2011-2012年以来，南哈德逊湾的北极熊数量也减少了17%，它们的身体状况也同样与更长的无冰期有关。