Point by point - because Ithink this is important, not so much because of the species extinction rate issue but because of the underlying issues of a lot of people not undersanding biology and environmental science:

Okay, I'm no biologist, so maybe I'm just ignorant. How the hell do you rationally come up with a number that declares that 97 percent of species have not yet been discovered?

An "estimate" of anywhere from 2 to 100 million species? Oh, hell, call it 50 million.

Are you even listening to yourself? I've seen people pull numbers out of their asses in many fields, but most are at least subtle about it.

That was an estimate, not a declaration. There are many studies that have tried to determine how many species remain to be discovered, but it's no simple task, hence the wide range of estimates. It's like scattering an unknown number of marbles in a huge forest, picking up most of the marbles in few square meters and trying to figure out how many you haven't found yet in the remaining thousand square kilometers. You can make an educated guess, but when you don't know if they were evenly distributed or not, it's only a guess. But if the total number is important, you have to guess, and make every effort to guess as accurately as possible. You have to have a starting point.

Cripes, I wish I could do engineering like this.

"Hey, Brosz, how thick does that propellant tank wall have to be?"

"Oh, anywhere from a tenth of an inch to two feet. Let's settle on a foot."

"Swell. A hundred-ton propellant tank."

"Bet it won't burst, though."

And it would be nice if one could do biology, or any life science, like that.

"Hmm, let's see, if we allow 34,224 species to become extinct, the world will go on without any significant effect, but if 34,225 die out, the world ecosystems will totally collapse."

"Yeah, and if we permit x tons of CO2 to be emitted into the atmosphere every year, climate will be unaffected, but if it's x + 1% we will be thrown into a sudden oscillation that will rsult in an ice age that will end civilization as we know it."

Sorry, but it doesn't work that way. Best educated guesses have to be made, and actions taken based on these, using a "bad case scenario" (not worst case) for reference. Unexpected problems result if not. Some joker figured that a couple of rabbits in Australia couldn't possibly be a problem in 3 million square miles. And there are countless other such situations that we don't have much of a clue how they will turn out... maybe good, maybe indifferent, maybe bad, but efforts must be made to at least try to determine the consequences in advance.

To use an engineering example - you must be familiar with the concept of unexpected consequences: some engineer designed the foam panels on the space shuttle. It's light, soft stuff, and nobody ever thought of what might happen if a chunk broke off during launch. Those panels were engineered to the millimeter or better, they did a good job, but look what happened.

And when it comes down to it, if a thousand species, or ten thousand species, or fifty billions species become extinct that nobody ever saw or heard of, and the environment goes on without a hiccup, what the hell does that mean anyway? If the last specimen of an unknown tree falls in a forest, does it make a sound?

Tom, you get upset with people who freak out about anything to do with nuclear power, because they don't understand it properly.

Can you say "biodiversity"? Yes it has been used politically, but that doesn't make it an invalid concept.

There is a good discussion on biodiversity here but I imagine you will dismiss it as vaporware. I hope you read it and think about it.

Do you also realize that not only does this "30,000" number have to be accepted, but then they also have to prove that this extinction rate has changed due to human activity?

Compared to this kind of vaporware, the Fermi Equation is nailed down to the last decimal point.

And you're the people who laughed their asses off when the subject of "weapons unaccounted for" came up as possible evidence that they still existed somewhere.

Environmentalism is used as a political weapon, and to do so, it requires that humanity, and especially capitalist industrialism, has to be shown to be doing irreparable and massive damage. If the proof isn't there, assuming damage exists based on guesses is not sufficient.

I'm seeing a LOT of politically-motivated research that works like this lately.

Yes, environmentalism is used as a political weapon, but it is also used for many valuable scientific purposes. Don't throw the baby out with the bathwater.

Assuming damage doesn't exist or won't happen could be even more dangerous than the obverse.

Politically motivated research needs to be examined critically and discarded if it is shown to be invalid, but remember it happens on both sides.

We cannot afford to be paralyzed by worst case scenarios, but neither can we afford to rush blindly into the future without making our best effort at determining the consequences of our actions - before we take them.