With time environmental issues got much more complicated. It is pretty easy, if you know what you are doing, to stop a company from pouring poison into a lake where kids swim. It is much harder to address all the myriad greenhouse gases emitted by different sources - from petrochemical refineries to hundreds of millions of peasants cutting down trees for their incredibly inefficient cook stoves.

As a student of conservation biology, I believe that characteristics with survival value will ultimately prevail. There is no survival value in pessimism. If you think failure is inevitable, that view will probably become self-fulfilling.

I suppose I'd characterize myself as having a faith-based optimism. My faith is parental and Darwinian.

An acre of windy prairie could produce between $4,000 and 10,000 worth of electricity per year - which is far more than the value of the land's crop of corn or wheat.

It is already too late to avoid mass starvation.

We've made some heroic efforts, but the Earth as a whole is in worse shape today than 30 years ago, ... There's been 30 more years of greenhouses gases, species extinctions and population growth.

By 1975 - and continuing to today - all Americans came to believe that they had a "right" to a safe, clean, healthy environment. When I grew up, no one seriously criticized the steel mills and paper mills for the deadly stench they produced - that was the smell of prosperity. In the modern society, no one would tolerate such conditions in an American city.