Mr. Darwin carefully observed the effects produced by planting a
few hundred acres of Scotch fir, in Staffordshire, on part of a very
extensive heath which had never been cultivated. After the planted
portion was about twenty-five years old he observed that the change in
the native vegetation was greater than is often seen in passing from
one quite different soil to another. Besides a great change in the
proportional numbers of the native heath-plants, twelve species which
could not be found on the heath flourished in the plantations. The
effect on the insect life must have been still greater, for six
insectivorous birds which were very common in the plantations were not
to be seen on the heath, which was, however, frequented by two or three
different species of insectivorous birds. It would have required
continued study for several years to determine all the differences in
the organic life of the two areas, but the facts stated by Mr. Darwin
are sufficient to show how great a change may be effected by the
introduction of a single kind of tree and the keeping out of cattle.
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