Gleick's claim is simply not supported by the evidence. The butterfly may produce a typhoon but it also may avert a typhoon. The natural system is extremely resilient. I make no such assumption, but you are in trouble with your eco folk if you are placing primary value on the human species. I do so, but if you want to join me, you have no argument with me but with those who see human beings as having no more value than snail darters.
Past experience shows that when people do that they come up with solutions.
The future of our planet is in the balance. The second quote is hardly support for the first. If I say that you must be careful when you cross the street or you may be hit by a car, I have not said that you have already been hit by a car. There certainly is consensus that the ecological effects of our actions must be taken into account or else there will be dire consequences. Lots of people and corporations are working on reducing resource consumption and avoiding environmental damage.