Here's a little line I pulled from the following article:
World examines "impossible" goal to halt extinctions
"The world has made some progress since 2002, such as in expanding protected areas for wildlife. But U.N. studies say extinction rates are running up to 1,000 times higher than those inferred from fossil records in the worst crisis since the dinosaurs were wiped out 65 million years ago."
I hate to play Devil's Advocate here: I'm invested in environmental causes as well, and I'm not making light of the very real and detrimental impact mankind is having on the ecosystem. But as someone that values fact and solid science over histrionics I kinda have to point this out...
Our fossil records have given us a wealth of information, and I personally find paleontology fascinating. But on the whole, they aren't very detailed at all. We're not even seeing 1% of the animals that ever existed. We can look at fossils of trilobites, stegosaurs and the like, but with us missing so much of the record it's very difficult to place these species into context. We can infer what role a creature or plant served in the ecosystem based on analysis of its features (it's clear stegosaurs weren't carnivores, for example), but we almost never get to see anything in the way of internal organs which can be vital in deciphering what these organisms were actually like. Nature throws us curve balls all the time, and it takes a very sophisticated eye to catch some of them. But there's not enough left to see in extinct animals to catch those, see? And without a detailed analysis of all the organisms that existed in a given time and location -- not just megafauna, but plants, insects, bacteria, and other subtle things that are vital to the ecosystem -- we can only make broad inferences about what an ecosystem was like and what organisms that comprised it might have done. Often we have to fill in gaps with educated guesses ("This was a herbivore, so there had to have been plants around")... filling in pieces of great puzzles most of whose pieces are long gone. Since most organisms that have ever existed have left us absolutely no trace of their existence, we can't really determine at what rate they went extinct. (I'd make an exception for the K-T Event, in which a great number of plants and animals went extinct; however, the KTE can't be considered typical of extinctions.)
So statements like "Extinction rates are running up to 1,000 times higher than those inferred from fossil records" sound like the sort of alarmist pseudo-science people tend to throw out all the time. For me to buy this I'd have to see strong evidence for it, and from what I've seen it just isn't there. And just as I roll my eyes at such declarations, there are a double handful of skeptics out there that know enough science to rip such assertions to shreds.... and with a lot more relish than I have. This doesn't do anything to help the environmental movement. But it does give opponents ammunition to use against it, and makes environmentalists look like left-wing fringers and worryworts relying on faulty science. It doesn't matter if this is the case or not, if that's how we're perceived that's bad for us. That's why we have to ground our assertions in hard science and verifiable fact, things not so easily dismissed.
And, again, I'm not some pundit trying to deny or downplay humanity's impact on the ecosystem. But isn't it enough to simply point out the facts of what we're doing, instead of comparing current trends to almost entirely theoretical models of past extinctions?