It is not a sentimental, but ...

It is not a sentimental, but a grimly literal fact that unless we share this terrestrial globe with creatures other than ourselves, we shall not be able to live on it for long.
 Joseph Wood Krutch

Quotes from the same author

Technology made large populations possible; large populations now make technology indispensable.
 Joseph Wood Krutch
It is not ignorance but knowledge which is the mother of wonder.
 Joseph Wood Krutch
To those who study her, Nature reveals herself as extraordinarily fertile and ingenious in devising means, but she has no ends which the human mind has been able to discover or comprehend.
 Joseph Wood Krutch
An abundance of some good things is perfectly compatible with the scarcity of others; that life is everywhere precarious, man everywhere small.
 Joseph Wood Krutch
When a man wantonly destroys one of the works of man we call him a vandal. When he destroys one of the works of god we call him a sportsman.
 Joseph Wood Krutch