Monday, June 11, 2012

Extinction of Plants


Plant extinctions have followed the same pattern as animal extinctions. Destruction of environment, particularly on isolated islands, has led to the most dramatic losses. On Hawaii, for example, about 300 plant species have become extinct within the last 300 years. On St. Helena, only 20 of over 100 species of native plants survive and of these 15 are in danger of extinction. It is said that of Barbados all native trees were felled within 40 years of the island’s discovery by European.
Just as an animal species may depend on one plant for survival, the reverses may also be true. For instant, the dodo tree, once abundant in Mauritius, has been reduced to 13 very aged trees since the extinction of the dodo, which ate and dispersed its seeds.
Commercially valuable plants have often been exterminated by over exploitation. Mauritius ebony and Sanfernandez sandalwood are both extinct, examples of felling without provision for regrowth. The wine palm of Dominica, tapped to make spirit in a way that killed it, became extinct in the 1920s.
Habitat destruction is the greatest threat to plant and animal species worldwide. In some cases, such as felling of tropical forests or draining of wetlands, damage is frequently done under the impression that the environment is being improved for human food production or habitation. In others, lack of understanding of the importance of particular environment in the life cycles of certain species has led to their downfall. Drainage of mangrove swamps, nurseries for many kinds of fish.