school energy&environment

Extinction of species

Worst problem of the degradation of the earth certainly is the decrease in biodiversity, i.e. the disappearance of thousands of animal and vegetal species, which are fragile ecosystems. Biodiversity is our basic natural resource, our biological wealth, and the human species depends on it for survival; the disappearance of a species is an irreversible phenomenon, so that once it has disappeared it has disappeared forever. Researchers argue that the destruction of tropical forests will be the main reason for the extinction of thousands of species over the next decades. Some think that between 5 and 15% of the species that exist today will be dead by 2020. Others believe that over 15,000 species will die every year in tropical forests only. These figures only concern the fast extinction resulting from the destruction of habitats, not to mention the long-term ones due to the reduction and fragmentation of habitats. The future certainly does not look rosy: 98% of the species that are doomed to disappear live in tropical forests. Many species are so well adapted to live in small geographical areas as to be threatened with extinction if their habitats are damaged. For instance, the golden toad (Bufo periglamus), discovered as late as 1964, lives on the top of the Monteverde in Costa Rica. After about one hour’s cutting of the forest to produce timber, its only habitat would be fatally damaged and it would dye.
Endangered species
The species most at risk of extinction are as follows:

• predatory species, especially those at the highest levels of the food chain of an ecosystem, which consist of few individuals and are spread on large surfaces (such as the jaguar);
• large-size animals with a low birth rate (such as the gorilla);
• species living in specific areas only, such as the endemisms of islands or secluded mountains, where habitats can be quickly and easily destroyed (such as the lemurs of Madagascar);
• very specialised species with poor adaptability, colonisation and spreading (such as the Amazonian hummingbird, whose beak is specialised to reach the nectar of the flowers of some passionflowers).