I think the cost of energy will come down when we make this transition to renewable energy.

No one should be able to enter a wilderness by mechanical means.

The only way forward, if we are going to improve the quality of the environment, is to get everybody involved.

We won't have a society if we destroy the environment.

It seems that every time mankind is given a lot of energy, we go out and wreck something with it.

Birds are indicators of the environment. If they are in trouble, we know we'll soon be in trouble.

By polluting clear water with slime you will never find good drinking water.

If we do not permit the earth to produce beauty and joy, it will in the end not produce food, either.

Keep close to Nature's heart... and break clear away, once in awhile, and climb a mountain or spend a week in the woods. Wash your spirit clean.

Our world faces a true planetary emergency. I know the phrase sounds shrill, and I know it's a challenge to the moral imagination.