I have no doubt that the fundamental problem the planet faces is the enormous increase in the human population

No one will protect what they don't care about, and no one will care about what they have never experienced.

The truth is: the natural world is changing. And we are totally dependent on that world. It provides our food, water and air. It is the most precious thing we have and we need to defend it.

Instead of controlling the environment for the benefit of the population, perhaps we should control the population to ensure the survival of our environment

What humans do over the next 50 years will determine the fate of all life on the planet.

Anyone who believes in indefinite growth on a physically finite planet is either mad or an economist

The World is full of wonders, but they become more Wonderful, not less Wonderful when Science looks at them.

The question is, are we happy to suppose that our grandchildren may never be able to see an elephant except in a picture book?

How could I look my grandchildren in the eye and say I knew what was happening to the world and did nothing.

Bringing nature into the classroom can kindle a fascination and passion for the diversity of life on earth and can motivate a sense of responsibility to safeguard it.

I just wish the world was twice as big and half of it was still unexplored.

We can all agree that children are ugly.

Of all the comforting objects in this world, few things are as reassuring and accepting as books.

As a child crawls up into his daddy's lap, we too can climb into our Father's arms and tell Him all that is in our hearts.

If our tears do not lead us to act then we have lost the reason of our humanity, which is compassion.

Market prices are always wrong.

As my mother once said: The boys throw stones at the frog in jest. But the frogs die in earnest.

Reason is not what decides love.

Some disappointment is always the price of brave dreaming.

Genius consists not in making great discoveries, but in seeing the connection between small discoveries.