Question

Why are (i) alien species invasion and (ii) loss of habitat and fragmentation, considered to be the major cause of loss of biodiversity? Explain with help of one example each.

Answer 1

Hint: Biodiversity is the vast array of species of micro-organisms, algae, fungi, plants, and animals occurring on the earth either terrestrial or aquatic habitats or the ecological complexes of which they are apart.

Complete answer: Destruction of habitats and fragmentation :
Habitats are destroyed by various human activities developmental work, deforestation, pollution cleanliness, etc.
Developmental work: human settlements, harbors, dams, reservoirs, roads, railway lines, croplands, pastures, plantations, industries, mines, etc. have reduced the natural habitats of wildlife.
Deforestation: deforestation deprives wildlife cover and food. This leads to a decrease in the population of species
Example -The most dramatic examples of habitat loss come from tropical rain forests. Once covering more than 14 percent of the earth’s land surface, these rain forests now cover no more than 6 percent. They are being destroyed fast.
The Amazon rain forest (it is so huge that it is called the ‘lungs of the planet’) harboring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle
Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines.

Alien species invasions:
When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive and cause decline or extinction of indigenous species.
Example -The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.

Note: The other causes of loss of biodiversity include co extinction, overexploitation, forest fires, etc.