(46) Scientists jumped to the rescue with some distinctly shaky evidence to the effect that insects would eat us up if birds failed to control them
翻译：科学家们匆匆赶来救援，但证据是明显站不住脚的。大意就是，如果鸟不能控制这些虫子，虫子就会吃光一切。
解析：
1. 句子主干为Scientist jump to the rescue. With引导jump的伴随状语，to the effect that 是evidence的同位语从句。If从句是该同位语从句中的条件状语从句。
2. Jump to sth表示“匆匆......”, 例如jump to a conclusion表示“匆匆得出结论”； to the effect that 是固定搭配，表示“大意是...”
(47) but we have at least drawn near the point of admitting that birds should continue as a matter of intrinsic right, regardless of the presence or absence of economic advantage to us.
翻译：但是，我们至少比较一致的认可这样一种观点，即：无论鸟类对我们是否具有经济价值，他们都应该继续享有其固有的生物权利。
解析：
1. 句子主干是We have drawn near the point；Of admitting是介词短语做定语，修饰point，；之后的that...是admit的宾语从句；regardless of ...是作让步状语。
2. draw near the point of，意为“接近......”, as a matter of, 意为“作为......”, regardless of,意为，“不管，不顾”，引导让步状语。
(48) Time was when biologists somewhat over worded the evidence that these creatures preserve the health of game by killing the physically weak, or that they prey only on “worthless species”.
翻译：生物学家们曾一度滥用这个证据：这些生物通过残杀弱者来维持生物链条的健康发展，或者只是捕食“无价值的物种”。
解析：
1. 句子主干是“Time was when ...”. when引导表语从句，两个that从句是evidence的并列同位语从句
2. Time was when，意为“曾经，从前”，prey on，意为“捕食”
(49) In Europe, where forestry is ecologically more advanced, the Non-commercial tree species are recognized as members of native forest community, to be preserved as such, within reason.
翻译：欧洲的林业生态发展比较先进。，那些没有商业价值的树种被视为原始森林群落的成员而被合理保护。
解析：
1. 句子主干是the Non-commercial tree species are recognized as members of native forest community；Where引导定语从句修饰Europe，充当句子的地点状语。
2. be recognized as意为，“被看做”； within reason， 意为“合情合理的”
(50) It tends to ignore, and thus eventually to eliminate, many elements in the land community that lack commercial value, but that are essential to its healthy functioning.
翻译：这样的体系容易忽视、并最终灭绝了生物群落中的许多元素。然而这些元素虽然缺少商业价值，但对整个群落的健康运动却至关重要。
解析：
1. 句子主干是It tends to ignore and to eliminate...；两个that分别引导定语从句修饰elements，意义上为转折关系。
2. Tend to do sth.意为“倾向于做某事”; be essential to sth，意为“对......必要的”
