Enlist four causes that may lead to the loss of biodiversity.
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Solution
The
world is facing accelerated rates of species extinctions, largely due to human
activities. There are four major cause of biodiversity losses, called as ‘The
Evil Quartet’.
Habitat loss and fragmentation: It is the most important cause
driving animals and plants to extinction.
When people cut down trees, fill a
wetland, plough a grassland or burn a forest, the nature habitat of a species
is changed or destroyed. These changes can kill or focus out many plants,
animals and microorganism as well as disrupt complex interaction the species. The
amazon rain forest harbouring 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 man y habitats by pollution
also threatens the survival of many species. Pollution may reduce and eliminate
populations of sensitive species. For example, pesticide linked decline of
fish-eating birds and falcons.
Large habitats and broken into small fragments in
habitats fragmentation. It is due to various human activities like human
settlements, building of roads, digging of canals etc. Forest patched having
croplands, orchards, plantations and urban settlements on their outskirts are examples
of fragmented habitats. Animals requiring large territories and migrating
animals are badly affected, leading to population declines.
Over-exploitation: Humans
have always dependent on nature for food and shelter, but when need turns to
greed, it leads to over-exploitation of nature resources. It means, biological
systems should not be exploited beyond the degree of their renewability. Overexploitation
of a particular species reduces size of its population to an extent so that it
become vulnerable to extinction. Dodo, Steller’s sea cow and Passenger pigeon
have become extinct in the last 500 year due to overexploitation by humans.
Alien
species invasions: New species entering a geographical region are called exotic
or alien or non-nation species. When alien species are introduced
unintentionally or deliberately for whatever purpose, they may cause
disappearance of nation or indigenous species through changed biotic
interactions. For examples, carrot glass is a weed which came into-India as a
contaminant with imported wheat. It has occupied all open areas extermination
many herbs and shurbs.
Co-extinctions: there are many obligate associations
amongst different species in ecosystems. When one of them become extinct, the
plants and animals species associated with it in an obligatory way also become
extinct. For example, coevolved plant-pollinator mutualism will result in
extinction of one partner if the other is eliminated in nature. If the host
fish become extinct, all the parasites exclusively found on it will also become
extinct.