Which argument? That if a species is truly on the verge of extinction, you would not want to be the one to make it extinct, however, you would want to be reimbursed for doing the right thing?
I do think there may be situations that society may need to pay people for losses incurred when society deems it important. That's what the political process is about. However, if all a person is concerned about is being reimbursed for doing a good deed, it's not much of a good deed, is it?
Why must every species of critter on Earth continue to have descendants forever?
I'd really like to know.
You speak as if this is some kind of huge benevolent concession on your part. In fact compensation for property which is taken for public use is REQUIRED by the Constitution. Perhaps you've heard of it? I know that most enviro-pagans wish it didn't exist, and pretend that it doesn't, anyway....