George Perkins Marsh quotes:

Man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords.

Sight is a faculty; seeing is an art.

The equation of animal and vegetable life is too complicated a problem for human intelligence to solve, and we can never know how wide a circle of disturbance we produce in the harmonies of nature when we throw the smallest pebble into the ocean of organic life.

Wherever modern Science has exploded a superstitious fable or even a picturesque error, she has replaced it with a grander and even more poetical truth.

All Nature is linked together by invisible bonds and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life.

Apart from the hostile influence of man, the organic and the inorganic world are ... bound together by such mutual relations and adaptations s secure, if not the absolute permanence and equilibrium of both ... at least a very slow and gradual succession of changes in those conditions. But man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords.

The great question, whether man is of nature or above her.

The improvement of forest trees is the work of centuries. So much more the reason for beginning now.

We have now felled forest enough everywhere, in many districts far too much. Let us restore this one element of material life to its normal proportions, and devise means for maintaining the permanence of its relations to the fields, the meadows and the pastures, to the rain and the dews of heaven, to the springs and rivulets with which it waters down the earth.

When not protected by law, by popular favor or superstition, or by other special circumstances, [birds] yield very readily to the influences of civilization, and, though the first operations of the settler are favorable to the increase of many species, the great extension of rural and of mechanical industry is, in a variety of ways, destructive even to tribes not directly warred upon by man.

Man has too long forgotten that the earth was given to him for usufruct alone, not for consumption, still less for profligate waste.