What are the main threats to biodiversity?
Threats to Biodiversity
i) Habitat degradation and its loss: Tropical forests harbour more than 50% of the biodiversity. Deforestation is the main cause of species extinction in these forests. Forests and grass lands are continuously being changed to agricultural land. Natural wetland systems have been drained to establish croplands, resulting in the loss of aquatic species. Multistory-natural forests are converted into forests of teak, sal etc., biodiversity is changed. Repeated fires in the forests by locals, reduce the regeneration and lower the biodiversity.
ii) Invasion of nonnative species: The widespread introduction of exotic species by humans is a potent threat to biodiversity When exotic species are introduced to ecosystems and establish self-sustaining populations, the endemic species in that ecosystem that have not evolved to compete with the exotic species, may not survive. The exotic organisms may be predators,, parasites, or aggressive species that deprive indigenous species. For example Established exotic species, Nile perch reduced the endemic species of great African lakes Victoria, Malawi and Tanganyika. Lantana bushes, Eupatorium shrub, Parthenium, Hyacinth, introduced into our ecosystems, spread at the expense of wild species.
iii) Species interdependence: Clavaria major, exclusive tree on Mauritius, seeds germinate when pass through the abrasive gut of Dodo bird. These birds became extinct in 17th century, only a few old trees survive now. Clavaria became endangered species.
iv) Erosion of barriers: The rich diversity of unique species across many parts of the world exist only because they are separated by barriers, particularly seas and oceans, from other species of other land masses, particularly the highly fecund, ultra-competitive, generalist “super-species”. These are barriers that could never be crossed by natural processes, except for many millions of years in the future through continental drift. However humans have invented ships and aeroplanes, and now have the power to bring into contact species that never have met in their evolutionary history, and on a time scale of days, unlike the centuries that historically have accompanied major animal migrations. As a consequence of the above, if humans continue to combine species from different ecoregions, there is the potential threat that the world’s ecosystems will end up dominated by a very few, aggressive, cosmopolitan “super-species”.
v) Pollution: Pollutants enter environment. They enter the organisms through biomagnification reducing their life-span. As a result the predatory organisms that depend on them may harmed. Pollutants also change the quality of environment, which is a prerequisite for the survival of organisms.
vi) Over exploitation of resources: The overuse or misuse of resources threatens the earth’s biodiversity. Logging, hunting, poaching, fishing etc. reduce the species in ecosystems.
vii) Change in the global environment: A change in the environment threatens the species and ecosystems.