We have an obligation to live in harmony with God's creation.
- Bruce Babbitt

Everything you do, and everything you do not do,
is your legacy to future generations.
- Jonathan Lockwood Huie

Treat the earth well.
It was not given to you by your parents,
it was loaned to you by your children.
We do not inherit the Earth from our Ancestors,
we borrow it from our Children.
- Native American traditional

A man is ethical only when life, as such, is sacred to him,
that of plants and animals as that of his fellow men,
and when he devotes himself helpfully to all life that is in need of help.
- Albert Schweitzer

Be gentle with the earth.
- Tenzin Gyatso, the 14th Dalai Lama

Further reading:

Plant Trees For Your Grandchildren

The World We Leave Our Children

The Seeds You Plant

All Life