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Now listen to part of a lecture on the topic you just read about.
现在来听一段关于你刚刚听到的话题的演讲。
Unfortunately, we still don't know what is killing the yellow cedar.
很遗憾，我们仍然不知道是什么在扼杀黄杉。
None of the explanations discussed in the reading is adequate.
阅读中讨论的解释没有一个是适当的。
First, the cedar bark beetle.
首先，杉树树皮甲虫。
Well, the problem with this explanation is these healthy yellow cedars are generally much more resistant to insect infestation than the other tree species.
嗯，这个解释的问题在于这些健康的黄杉一般来说比其他树种对害虫入侵更有抵抗力。
For example, the bark and leaves of the yellow cedar are saturated with powerful chemicals that are poisonous to insects.
比如，黄杉的树皮和叶子上饱和着对于昆虫来说有毒的强力化学物质。
So healthy cedars are unlikely to suffer from insect damage.
所以健康的黄衫不会遭受昆虫破坏。
So how can we explain those dead cedars that were infested with beetles?
那么，我们该如何解释那些寄居着甲虫的死杉树呢？
In those cases, the beetles attack trees that were already damaged or sick, and would have probably died anyway.
在那些情况里，甲虫侵袭的是已经受损或者患病，也许不论如何都会死掉的树。
So the beatles are not the fundamental cause responsible for the decline of the yellow cedars.
所以，甲虫不是导致黄杉减少的根本原因。
Second, although bears damage some trees, they are not the cause of the overall population decline.
第二，虽然熊破坏了一些树木，它们不是总体数量减少的原因。
Yellow cedar population has been declining all across of the Northwestern coast of North America, both on the mainland and on islands just off the coast.
在北美西北部整个海岸线上的黄杉数量都在下降，不管是在大陆还是在离岸的岛屿上。
There are no bears on the islands, yet the islands cedars are still in decline.
那些岛屿上没有熊，而黄杉的数量依然在减少。
Since the decline occurs with and without bears, the bears cannot be responsible.
因为（数量）减少有没有熊都在发生，所以熊不会是其原因。
And finally, the theory about the roots suffering from frost damage.
最后，关于树根遭受霜冻害的假说。
Well, the reading passage forgot to take one fact into account.
嗯，阅读文章忘记了考虑一个事实。
Many more trees are dying at lower elevations where it is warm than at higher elevations where it is cold.
温暖的低海拔处比寒冷的高海拔处正在死去的树更多。
If freezing damage were responsible for the decline, we would expect to see more trees dying in the cold weather of high elevations.
如果冻害是（数量）减少的原因，我们将会看到在寒冷的高海拔地区更多的树死去。
Instead, more trees are dying in the relative warmth over the lower elevations.
反而，在相对温暖的低海拔处更多的树正在死去。
So, although the climate change may have made the cedar roots more sensitive than they used to be, this isn't what is killing them.
所以，尽管气候的变化可能已经使杉树的树根比以前更加敏感，但是这不是扼杀它们的事情。
