What doesn't bring down the number of polar bears according to this passage?
根据这篇文章，是什么没有减少北极熊的数量？
They have pushed down the number of polar bears and seals while polar bears depend on sea ice for hunting seals.
它们导致了北极熊和海豹数量的减少，而北极熊依靠海冰捕食海豹。
According to a study in Nature Climate Change, the number of most polar bears will fall rapidly by 2080.
据《自然气候变化》的一项研究显示，到2080年，几乎大多数北极熊的数量都将急剧减少。
Another is that the number of humans who venture into polar bear territory remains somewhat low.
另一个理由则是，冒险进入北极熊领地的人还是少之又少的。
Nobody knows the exact number of polar bears.
没有人知道北极熊的确切数量。
A great number of polar owls, white geese, brant geese, Arctic foxes, walruses and other animals live here.
大量的白猫头鹰，白鹅，黑雁，北极狐，海象以及其它动物在这里生存。
When out of the water, Arctic seals are in danger of being eaten by the region's number one killer-the polar bear.
一旦离开了水，北极海豹就面临着被区域头号杀手——北极熊吃掉的危险。
The Dutch mountaineer, who already scaled Everest without supplementary oxygen and attempted K2 twice before, also has a number of spectacular polar expeditions to his credit.
这个荷兰登山者，已经无氧攀登了珠峰，在之前又尝试两次攀登K2，拥有非常丰富的极地探险经验。
The mode number of chromosomes also varies with the multiple polar spindle rates from 61 to 62 after simulated microgravity for 72hours.
伴随着纺锤体多极率的增加，微重力72小时后，细胞的染色体众数由61变为62。
The surface of the treated fibre contains more hydrophilic groups of oxygen and nitrogen. The increase of the number of polar surface groups accounts for the increase of fiber cohesion.
等离子体处理兔毛引起其表面性能变化的原因是由于表面极性基团增加的缘故。
Saturn's southern polar region is haunted by a number of dark storms in this image, including one storm at right of center with a slight brightening around its boundary.
在这张照片里，土星南极区域被一些黑色的风暴所骚扰，其中包括一个位于中心偏右的，边缘有些发亮的风暴。
Furthermore, polar coordinate targeting and a high-resolution fiberoptic camera enable an increased number of biopsies to be performed, enhancing facility workflow and throughput.
极性协调目标定位和高清晰度光纤相机，允许提高活检次数，提高工作流程和工作通量。
Furthermore, polar coordinate targeting and a high-resolution fiberoptic camera enable an increased number of biopsies to be performed, enhancing facility workflow and throughput.
极性协调目标定位和高清晰度光纤相机，允许提高活检次数，提高工作流程和工作通量。
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