The main causes of biodiversity loss include land ‑use change, changing levels of atmospheric carbon dioxide, changing climate, biological invasion and nitrogen deposits (air pollution). The causes of biodiversity loss are many and varied, and often interrelated.

Habitat loss
Habitat refers to the area where species seek food got shelter and reproduction the greatest threat to wild plant and animals species is due to destruction or alteration of their habitat if an animal habitat is destroyed or disrupted, it must adapt to the new change, move elsewhere or die. When it is forced out of its territory and if it finds a suitable habitat there is a possibility that the habitat already in use consequently it must compete with the local population of the same species as well as other animals the other option a that it must migrate into a marginal habitat where it may succumb to predation, starvation or disease . Some organism such as pigeon, house sparrows, rodent (like rat and mice) and deer flourish in the modified habitats provided by human activities but many other do not. Some habitats are move vulnerable to species extinction, these are called fragile habitats. Coral reefs, Oceanic island and mountain top are important fragile habitats.

Habitat destruction is recognised today as the most significant threat to global biodiversity and bears responsibility for much of the species loss worldwide This include:
- Felling of forest for land use(eg clear felling for development agriculture), large scale logging and small scale patchwork agriculture. Shifting cultivation alone is believed to be responsible for 70% of deforestation in Africa, 50% of Deforestation in Asia and 35% of Forest deforestation in America.
- Destruction of Mangrove sites for agriculture
- Mining and destruction of corals
- Conversion of wetlands for land use
- Over extraction of timber and fuel wood
- Human induced buring of habitats (eg forest firing for shifting cultivation and firing grasslands to improve fodder for cattle)
- Damming of rivers
- Siltation and Sedimentation of freshwater bodies
- Pollution also disturb the natural habitat considerably. Industrial wastes cause severe impact, particularly on the aquatic habitat. For example: during the 1950s and 1960s , Insecticides particularly chlorinated hydrocarbons, reduced the populations levels of several birds such as bald eagle and brown pelican.
Human Wild Life Conflict
People use some plant and Animals species at a greater rate than the species can replace themselves. Nine of the world’s major ocean fisheries are declining because of too much fishing as well as water pollution and habitat destruction, eg Southern bluefin tuna, the Atlantic halibut and the Pacific and Atlantic salmon.
Current logging rates threaten to eliminate mahogany and many other trees species that take many years to grow and mature.
the $10 billion a year market in wildlife — For pets, folk medicines, gourmet foods, decorative objects and other uses — threatens elephant and rhino, sea horses and colorful corals, tropical plants and birds, bears, pandas and tigers.
Selective Destruction Of Species
The selective destruction of one species of an existing fauna can produce equally unfortunate results. The perfect demonstration of unexpected. Consequences of such selective destruction can be explained to you by the example of Passenger pigeon. The passanger pigeon (Ectopistes migratorious ) was probably most abundant bird on earth as recently as the middle of the 19th century. Their flocks darkened the sky during migration and one such flock alone was 400 km long and had no less than two billion birds . so huge was their numbers that the branches of trees would break under the weight of the perching birds. It tools hours for the flocks to pass through a place . there used to be as many as 90 nests per tree throughout a stretch of forest of about 5km width and 67km length.
In 1871, an estimated 136 million passenger pigeons nested in a 2,299sq. Km area of central Wisconsin, USA. An immense tonnage of dropping fertilised the forests where passenger pigeons roosted. Today there is not even a single passenger pigeon on the earth . you must be wondering why this extinction occured . This happened because millions of passenger pigeons were killed for food every year
Domestication Of Selective Species
Humans have taken care of the living beings which are useful to them through extensive breeding programme, to derive maximum benefit of their products. During the process, the species have lost certain useful characteristics so much so that these forms cannot survive on their own in nature . a very good example is corn , which is pampered so kuch by humans that if is left on its own,its cannot survive.
Today human has large herds of domestic animals. These animals can also play a significant part in the reduce ruin of animal populations by overgrazing the kand, thus destroying the vegetation on which both thay and the wild animals depend. The native wildlife of a particular area is capable of utilising tye native plant life much more efficiently than introduced domestic cattle and is thus much less likely to convert fertile areas into deserts.
The other important parameter is that tge domestic cattle are carriers of several disease which can transmit to wild animals. For example, the steady rehabilitation of the greta indian Rhinoceros was seriously hampered by the rider diseases which they contracted from they contracted firm the local domestic cattle.
Use Of pesticides.
Pesticides harm insect pollinators , including managed honey bee populations, which can in turn reduce crop yields. Runoff seeping into rivers , lakes and coastal environment can produce negative impacts on entire aquatic ecosystems.
several pesticides banned in the united states are still exported to developing countries such as DDT, DDE and PCBs. These substances mimic or interface with normal hormones in living organisms. Reproductive abnormalities have been found in alligators, terns, salmon and gulls exposed to high levels of chemical from pesticides and animal hormones in their environment.
Global Climate Change
Substantial evidence demonstrate that people are contributing to measurable changes in the global climate , threatening life, by buri burning fossils fossils such as oil, natural gas and coal and by burning trees, we have dramatically increased the amount of CO2 in the atmosphere . while scientist do not know the exact effects of increased CO2 , they predict that it will lewd to higher overall global temperatures , increasing sea levels and changes in climate patterns.

The changed atmospheric condition that result from global warming could create greater numbers of intense storms and prolonged drought . on the other hamd , the expected speed of climate changes coupled with direct loss of natural habitat May prevent some species from adapting quickly enough. They are likely to become extinct , locally or more broadly and their roles in natural systems will be lost forever.