Island Life; Or, The Phenomena and Causes of Insular Faunas and FlorasWallace, Alfred Russel
Science
Island Life; Or, The Phenomena and Causes of Insular Faunas and Floras
Wallace, Alfred Russel
Biogeography; Glacial epoch; Island ecology
island and the coast of Africa, in a south-easterly direction, is a
profound oceanic gulf known to reach a depth of 2,860 fathoms, or 17,160
feet, while an equally deep, or perhaps deeper, ocean, extends to the west
and south-west, we shall be satisfied that St. Helena is a true oceanic
island, and that it owes none of its peculiarities to a former union with
any continent or other distant land.
_Change Effected by European Occupation._--When first discovered, in the
year 1501, St. Helena was densely covered with a luxuriant forest
vegetation, the trees overhanging the seaward precipices and covering every
part of the surface with an evergreen mantle. This indigenous vegetation
has been almost wholly destroyed; and although an immense number of foreign
plants have been introduced, and have more or less completely established
themselves, {295} yet the general aspect of the island is now so barren and
forbidding that some persons find it difficult to believe that it was once
all green and fertile. The cause of the change is, however, very easily
explained. The rich soil formed by decomposed volcanic rock and vegetable
deposits could only be retained on the steep slopes so long as it was
protected by the vegetation to which it in great part owed its origin. When
this was destroyed, the heavy tropical rains soon washed away the soil, and
has left a vast expanse of bare rock or sterile clay. This irreparable
destruction was caused in the first place by goats, which were introduced
by the Portuguese in 1513, and increased so rapidly that in 1588, they
existed in thousands. These animals are the greatest of all foes to trees,
because they eat off the young seedlings, and thus prevent the natural
restoration of the forest. They were, however, aided by the reckless waste
of man. The East India Company took possession of the island in 1651, and
about the year 1700 it began to be seen that the forests were fast
diminishing, and required some protection. Two of the native trees, redwood
and ebony, were good for tanning, and to save trouble the bark was
wastefully stripped from the trunks only, the remainder being left to rot;
while in 1709 a large quantity of the rapidly disappearing ebony was used
to burn lime for building fortifications! By the MSS. records quoted in Mr.
Melliss' interesting volume on St. Helena,[67] it is evident that the evil
consequences of allowing the trees to be destroyed were clearly foreseen,
as the following passages show: "We find the place called the Great Wood in
a flourishing condition, full of young trees, where the hoggs (of which
there is a great abundance) do not come to root them up. But the Great Wood
is miserably lessened and destroyed within our memories, and is not near
the circuit and length it was. But we believe it does not contain now less
than fifteen hundred acres of fine woodland and good ground, but no springs
of water but what is salt or brackish, which we take to be the reason that
Public-domain text, read in full here on John Shaqi.
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