Man …………………………

The balance of nature is a very elaborate and very
delicate system of checks and counterchecks. It is
continually being altered as climates change, as new
organisms evolve, as animals or plants permeate to
new areas. But the alterations have in the past, for the
most part, been slow, whereas with the arrival of
civilized man their speed has been multiplied many
fold. Everywhere man is altering the balance of nature,
sometimes deliberately, sometimes unconsciously. In
five thousand years he has done more to alter the
biological aspect of the planet than has nature in five
million, and many of these changes have had
unforeseen consequences.