[求助]GWD1-Q9 to Q12:一个句子翻译

haha666

Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption

翻译：虽然没人量化过人类扰乱造成的迷路率的变化，但我们没理由怀疑这种效果和SH山喷发造成的后果有质的区别。

请教两个问题：

1：没看到比较级，为什么这里有“than”？

2：这句话是人类活动产生的后果和火山喷发的后果作比较，是effect caused by human‘s activity compared with that  by eruption ，为什么原文中用了what？

[此贴子已经被作者于2009/8/3 21:51:22编辑过]

ellendong

different than 是固定搭配，不是比较
What 这里是引导从句.
example:

what you have done is different than what I had thought.

haha666

thanks for your response

第一个问题解决了

但第二个问题，我知道what是引导从句，但我觉的这里并不需要用what啊，用that不就行了？

the effect would be qualitatively different
                    than that was seen in the .....