How Polar Bears Adapt to Climate Change北极熊如何适应气候变化

A group of several hundred polar bears in south-eastern Greenland often catch seals by waiting outside their prey’s breathing holes on blocks of floating freshwater ice from glaciers， in an example of the animals adapting to a loss of sea ice driven by climate change. 在格陵兰岛东南部，冰川断裂形成淡水浮冰，数百只北极熊经常在浮冰上守着海豹留下的呼吸孔捕猎。这是动物适应气候变化所致海冰流失的一个例子。

A group of polar bears in south-east Greenland have adapted to hunt via blocks of freshwater ice from glaciers when sea ice retreats in the warmer months. This suggests the animals may be more resilient to climate change than we thought， although loss of sea ice remains the greatest threat to their survival.

格陵兰岛东南部的海冰会在暖季消退，而那里有一群北极熊已经适应了暖季在冰川断裂形成的淡水冰上捕食。这表明，尽管海冰流失仍是北极熊生存的最大威胁，它们或许比我们想象的更能适应气候变化。

Polar bears often hunt seals by waiting near holes in blocks of floating ice where their prey come up to breathe. Seals are also slower on ice than in water， giving polar bears an advantage. But this is being threatened by climate change and the resulting sea ice loss. As a result， the animals are projected to decline by 30 per cent over the next three polar bear generations.

北极熊经常守在浮冰上的孔洞附近，等海豹上来呼吸时抓捕猎物。此外，海豹在冰上移动的速度比在水中慢，这为北极熊带来了可乘之机。然而，气候变化及其导致的海冰流失正威胁着这一捕食方式。预计接下来3代北极熊的数量将因此减少30%。

“We provide evidence for a previously-undocumented and highly-isolated subpopulation of polar bears on the south-east coast of Greenland surviving in a special way，” says Kristin Laidre at the University of Washington in Seattle. “They survive in fjords that are sea-ice free for more than eight months of the year because they have access to glacier ice on which they can hunt.”

华盛顿大学西雅图校区的克里斯廷·莱德雷表示：“我们提供的证据显示，格陵兰岛东南海岸存在一个之前未被记录且高度独立的北极熊亚群，它们的生存方式很特殊。1年中的8个多月里，它们能在没有海冰的峡湾里生存下来，因为它们能去冰川冰上捕食。”

Laidre and her colleagues analysed genetic samples from polar bears that they tracked from 2015 to 2019， which they combined with data from previous studies. In their first discovery， they found a few hundred polar bears in south-east Greenland are the most gen-etically isolated of their species.

莱德雷和同事分析了他们从2015年到2019年追踪的北极熊的基因样本，并将样本数据与之前的研究数据进行比对。他们的第一个发现是，格陵兰岛东南部的几百只北极熊是该物种中基因独立性最高的。

While tracking these animals， the team further discovered this genetically-isolated group hunts via floating blocks of freshwater ice， broken off from glaciers， for about 250 days of the year， when sea ice has melted. This probably enables the bears to live in the area， which has no sea ice for considerably longer than other polar bear habitats.

在追踪过程中，研究小组进一步发现，这群基因独立的北极熊在海冰融化期间（1年约250天），能在冰川断裂形成的淡水浮冰上捕食。大概就是这种捕食方式让这群北极熊得以在格陵兰岛东南海岸生存下来，毕竟该地区的无海冰期要远长于其他的北极熊栖息地。

While this suggests all polar bears are more resilient than we previously thought， glacial ice is largely limited to the animals around Greenland and Svalbard.

尽管这表明所有北极熊都比我们以前想象的更具适应力，但能借助冰川冰的基本仅限格陵兰岛和斯瓦尔巴群岛周围的北极熊。

“Glacier ice may help small numbers of polar bears survive for longer periods under climate warming， and may be important to prevent extinction， but it is not available for the vast majority of polar bears，” says Laidre.

莱德雷说：“冰川冰或许能帮助少数北极熊在气候变暖的情况下存活得更久，或许对避免物种灭绝很重要，但绝大多数的北极熊没有冰川冰可用。”

“Climate action is the single most important thing for the future of polar bears. Most polar bears in the Arctic depend on sea ice.”

“就北极熊的未来而言，气候行动才是最重要的事情。北极的大多数北极熊依赖海冰。”

According to Todd Atwood at the United States Geological Survey， the findings “offer a ray of hope that other refugia habitats may be available for polar bears to use， so that they can persist until greenhouse gas emissions are substantially mitigated and sea ice habitat is recovered”.

根据美国地质调查局托德·阿特伍德的说法，研究结果“带来了一丝希望——北极熊或许可以利用其他生物庇护所，如此便可坚持到温室气体排放量大幅减少，海冰栖息地得以恢复”。

“But ensuring the long-term persistence of a [wild] population of polar bears is ultimately dependent on conserving their sea ice habitat. That will require mitigating greenhouse gas emissions.”

“但要确保（自然环境中的）北极熊群体能长期生存，最终还是要靠保护海冰栖息地来实现。这就需要减少温室气体排放。”

The genetically-isolated bears may have adapted to hunting via freshwater ice， but this doesn’t make them immune to the effects of climate change.

这群基因独立的北极熊可能已经适应了在淡水冰上捕食，但这并不能使它们免受气候变化的影响。

“I suspect the Achilles’ heel for this group of bears will be ongoing warming that negatively affects the ringed seal population in the area. If the ringed seals don’t have breeding habitat， the main prey of the bears may disappear，” says Andrew Derocher at the University of Alberta in Canada.

加拿大阿尔伯塔大学的安德鲁·德罗谢表示：“如果该地区持续变暖，我认为这群北极熊会面临灭顶之灾，因为持续变暖会对环斑海豹的数量造成负面影响。如果环斑海豹没有繁育栖息地，那么这群北极熊的主要猎物可能就会消失。”

（译者单位：中国航天科工集团二院）