Reasons for loss of Biodiversity


  • Habitat loss and fragmentation: This is a primary cause which drives animals and plants to extinction. The habitat loss and fragmentation have been through changes of land use, in particular, the conversion of natural ecosystems to cropland, development of infrastructure projects like rails and roadways, increasing urbanisation and mining activities.As per the Living Planet report, there has been about a 30% decline in wetlands in the last 40 years. Wetlands have been primarily reclaimed for agriculture and urbanisation. Also, about 50% of the tropical and subtropical forests and 45% of the temperate grasslands have been converted for human use.Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. When large habitats are broken up into smaller fragments because of different human activities, mammals and birds which require large territories and certain animals with migratory habits are adversely affected, causing a decline in their population.
  • Over-exploitation of species: Unsustainable use of ecosystems and over-exploitation of biodiversity are a major reason behind biodiversity loss. Over-hunting or poaching of species, overfishing and overharvesting of plant products can quickly lead to a decline in biodiversity. Changing consumption patterns of humans is often cited as the key reason for this unsustainable exploitation of natural resources. Many species which got extinct in the past 5 centuries, like Steller’s sea cow, passenger pigeon, were subject to over-exploitation by humans.
  • Introduction of alien species: Plants, animals and microorganisms transported deliberately or unintentionally from an outside geographical region can cause great damage to native species by competing with them for food and shelter, spreading diseases unknown to them, causing genetic changes through the process of interbreeding with native species, and disrupting various aspects of their food chains and the physical environment. For example, in India Water hyacinth was introduced by the British for beautification. But over time, it has become an invasive species, clogging rivers, lakes and other water bodies, thus not allowing any aquatic life to grow and survive.
  • Environmental pollution: The accumulation of Pollution such phosphorus and nitrogen largely from excess fertilizers running off farmland, harmful chemicals firm urban and suburban runoff, industrial effluents etc. which are discharged into the natural water bodies. For example, oil spill off the port of Ennore in Chennai in 2017. Similarly, plastic pollution causes the death of animals. Also, air pollution from industries and vehicles has resulted in the death of many bird species in urban areas.
  • Global climate change: Climate change is projected to become a progressively more significant threat to biodiversity in the coming decades. Already, changes in the flowering and migration patterns as well as in the distribution of various species have been observed throughout the world. These changes have altered food chains and created mismatches within ecosystems where different species have evolved synchronised inter-dependence.
  • Co-extinctions: When a particular species becomes extinct, the plants and animals associated with it in an obligatory way also come under the danger of becoming extinct. For example, When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
  • Natural causes: Like floods, earthquakes and other natural disasters also cause loss of biodiversity.