easy english这是高一课本中的年一句话,不理解句子成分The effect this will have on the local wildlife protection.The effect this 俩名词放一起?THAT有省略吗?还有：The English spoken in USA is different from that(为什么不用WHICH )spoken in England.

The effect 是 subject
this是一个pronoun, 代替前面所讲过的一个事情。

this应该是前文的某个成分的抽象指代，但绝对不是代指本句的the effect。这句话是：这（前文代指的事物）会对当地野生动物保护产生影响……。
这里的that指代的是前文的The English，而非一个定语从句，故不能用which替代，因为which作代词时是没有实际意思的，而that则可确确实实地替代前面的成分。这句话理解为：The English spoken in the US is different from the English spoken in England.

"The effect" {subject} and "this" {noun} can be used together due to the grammatical acceptance of this type of sentence structure.
Another example will be "The feeling this song brings out is peaceful." In which "The feeling" is the subject and "this song" is the noun.
For "The English spoken in USA is different from that spoken in England." Using "which" instead if "that" is not possible,"that" is a replacement for "the English" and cannot be replaced with "which" {a prerogative pronoun}.
This sentence actually means:
The English spoken in the US is different from the English spoken in England.