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？

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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。

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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。

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La Polar has made a number of management changes recently, and new investors will have the opportunity to appoint three new board members at a special meeting on July 8th.

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Coke says it will distribute more than one billion white cans and roughly the same number of seasonal red cans, which also include polar-bear images.

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When Cluster II passes through these so-called polar cusps, instruments on board each of its satellites will measure the magnetic field, electrical current and number of charged particles within the tetrahedron.

ECONOMIST: Birds of a feather