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https://www.pbs.org/newshour/science/wolves-greenthumbs-yellowstone
¡°The question is: Do these changes have anything to do with the wolf reintroduction?¡± MacNulty said. ¡°Is it due to wolves scaring elk out of areas that are risky? Is it due to wolves driving elk numbers down, so there are few elk around to feed on these aspen trees?¡±
But that¡¯s a tough link to prove, because there are so many environmental variables at play. Most significantly, a multi-year drought was in full swing right around the same time as the wolf reintroduction. Aspen and willow trees need a lot of moisture to grow. In fact, MacNulty says there has been a long-term drying trend in Yellowstone since records started to be kept in the late 1800¡¯s.
It¡¯s a source of active debate and there is no consensus on whether the aspen decline was caused by long-term drought, over-browsing by elk, or a combination of the two, MacNulty said.
Ãâó : °í·Á´ëÇб³ °íÆĽº 2024-07-12 17:21:31: