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How large is the extinction debt, and when will it be paid?
Measure how many species are committed to delayed extinction by past habitat loss and fragmentation, and how long until they are lost.
比较改动
选两个分支看看改了什么，再发起 PR 把工作带过去。
选两个不同的分支
PR 可以从任何一个分支合入任何另一个分支。