The symbolism - and the substantive significance - of planting a tree has universal power in every culture and every society on Earth, and it is a way for individual men, women and children to participate in creating solutions for the environmental crisis.

Making consumer choices that reward eco-friendly products and companies is a great way to start.

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

The truth is that climate change is presenting the greatest challenge humanity has ever faced.

Politics has become a game of meaningless, mindless battles, conducted by unscrupulous methods and people, designed to transform even the most serious policy debates into sport.

Our insatiable drive to rummage deep beneath the surface of the earth is a willful expansion of our dysfunctional civilization into Nature.

There's lots about politics I don't feel comfortable with. To talk about the politics of future ideas is impossible in soundbite form.