I'd rather spend my leisure time doing what some people call my work and I call my fun.

In contrast [to trees and fish], oil, metals, and coal are not renewable; they don't reproduce, sprout, or have sex to produce baby oil droplets or coal nuggets.

The United States has long thought of itself as the land of infinite plenty, and historically we did have abundant resources. But now we are gradually exhausting our fisheries, our topsoil, our water. On top of that, we're coming to the end of world resources.

[T]he values to which people cling most stubbornly under inappropriate conditions are those values that were previously the source of their greatest triumphs.

The single most important problem is our misguided focus on identifying the single most important problem!

One person making a wrong decision affects the whole country.

The southward advance of native African farmers with Central African crops halted in Natal, beyond which Central African crops couldn't grow - with enormous consequences for the recent history of South Africa.