we decide that any part of the influence of man is novel
and anomalous, carefully to consider the powers of all other animated
agents which may be limited or superseded by him.[1002] Many who have
reasoned on these subjects seem to have forgotten that the human race
often succeeds to the discharge of functions previously fulfilled by
other species. Suppose the growth of some of the larger terrestrial
plants, or, in other words, the extent of forest, to be diminished by
man, and the climate to be thereby modified, it does not follow that
this kind of innovation is unprecedented. It is a change in the state of
vegetation, and such may often have been the result of the appearance of
new species upon the earth. The multiplication, for example, of certain
insects in parts of Germany, during the last century, destroyed more
trees than man, perhaps, could have felled during an equal period.

It would be rash, however, to affirm that the power of man to modify the
surface may not differ in kind or degree from that of other living
beings; although the problem is certainly more complex than many who
have speculated on such topics have imagined. If land be raised from the
sea, the greatest alteration in its physical condition, which could ever
arise from the influence of organic beings, would probably be produced
by the first immigration of terrestrial plants, whereby the new tract
would become covered with vegetation. The change next in importance
would seem to be when animals first enter, and modify the proportionate
numbers of certain species of plants. If there be any anomaly in the
intervention of man, in farther varying the relative numbers in the
vegetable kingdom, it may not so much consist in the kind or absolute
quantity of alteration, as in the circumstance that a _single species_,
in this case, would exert, by its superior power and universal
distribution, an influence equal to that of hundreds of other
terrestrial animals.

If we inquire whether man, by his direct power, or by the changes which
he may give rise to indirectly, tends, upon the whole, to lessen or
increase the inequalities of the earth's surface, we shall incline,
perhaps, to the opinion that he is a levelling agent. In mining
operations he conveys upwards a certain quantity of materials from the
bowels of the earth; but, on the other hand, much rock is taken annually
from the land, in the shape of ballast, and afterwards thrown into the
sea, and by th