气候变暖让灰熊弃荤从素改吃浆果

灰熊本是食肉动物，但是现在阿拉斯加科迪亚克岛的灰熊却放弃了鲑鱼而转而以浆果为主食，变成了“素食者”，这是怎么回事呢？

Grizzly bears have stopped eating salmon in favour of elderberries after being forced to make a choice due to climate change. Warming temperatures meant that the berries are ripening earlier than usual, at exactly the same time as the freshwater streams on Alaska’s Kodiak Island are overflowing with sockeye salmon.

由于气候变化的影响，灰熊被迫做出艰难抉择，放弃鲑鱼改吃接骨木果。温暖的气候使得浆果成熟期提前，与此同时，阿拉斯加科迪亚克岛的淡水河流里也挤满了红鲑。

The island's brown bears typically feed first on salmon in early summer, followed by elderberries later in the season, in late August and September.

往年，岛上的棕熊在夏初先吃了鲑鱼，然后在八月末和九月吃接骨木果。

"What you have is a scrambling of the schedule," said William Deacy, a biologist at Oregon State University that studied the phenomenon.

研究这个现象的俄勒冈州立大学的生物学家威廉•迪西称：“如今的生物成熟期十分混乱。”

"It's essentially like if breakfast and lunch were served at same time and then there is nothing to eat until dinner.

“这就好比早餐和午餐同时送上来，那么晚餐前就什么都没得吃了。”

"You have to choose between breakfast and lunch because you can only eat so much at a time."

“你必须在早餐和午餐间做抉择，因为你一次只能吃那么多。”

The study found that during the unusually warm summer of 2017, the bears, which would traditionally kill up to 75 percent of the salmon, were nowhere to be seen near the streams.

研究发现，在2017年，夏季异常温暖，但流水旁却不见灰熊的踪影。照往常来说，它们这时候可要吃掉高达75%的鲑鱼。

Instead, they were in the hills busy munching on berries, which contain less protein and therefore take less energy to break down, causing them to gain weight more quickly.

但是，它们一反常态，跑到山上大吃浆果。浆果里面的蛋白质含量低，消化分解所需能量少，因此它们长胖的速度也加快了。

Biologists warned that changes caused by a warming planet were behind the bears' unusual behavior and could affect the entire ecosystem.

生物学家们警告称，灰熊不寻常的行为背后反映的是全球变暖所带来的变化，可能会影响整个生态系统。

The researchers found that the forests around the streams suffered because the bears’ fish carcasses were no longer there to enrich the soil.

研究人员发现，没有灰熊吃剩的鱼骸来给土壤增肥，河流周围的森林已经受到了影响。

"Bears switched from eating salmon to elderberries, disrupting an ecological link that typically fertilizes terrestrial ecosystems and generates high mortality rates for salmon," the study said.

研究表明：“灰熊不吃鲑鱼改吃接骨木果的行为不仅破坏了滋养陆地生态系统的生态链，还促成了鲑鱼的高死亡率。”

On average, red elderberries are said to be ripening two and a half days earlier every decade.

据称，平均每十年，红接骨木果成熟的时间会提前两天半。

If the pattern continues, they will regularly overlap with the salmon by 2070.

如果再这样下去，到2070年，鲑鱼和接骨木果的成熟期将会定期重合。

The study was published in the Proceedings of the National Academy of Sciences.

这项研究成果已在《美国科学院学报》上发表。