1.       Loss of habitat: - Destruction and loss of natural habitat is the single largest cause of biodiversity loss. Habitat fragmentation is the division of habitat into small and scattered patches due to development of roads, industries etc in an original large habitat.

2.       Introduction of exotic species (alien species new to particular area):- Exotic species threaten native flora and fauna directly by predating or by competition and indirectly by altering the natural habitat or the exotic species may be disease causing species which might cause epidemic and kill the entire native species. eg. Water hyacinth is a weed which causes clogging supply of O₂ and nutrients present in water bodies and hence cause suffocation.

3.       Pollution and Global warming: - Pollution and global warming alter the adaptability of various species thus adversely affecting the plant and animal species. They put a stress on ecosystem.

4.       Illegal practices like hunting and poaching: - Illegal trade of wildlife products by killing prohibited endangered animals commercially wild animals and hunted for their produces such as skin, tusk, fur and decoration purposes. eg. Dodo has become extinct because of hunting.

5.       Improper use of agrochemicals, pesticides, inequitable land distribution etc adversely affects the life of many species.