Loss of Biodiversity

Loss of biodiversity means the decline or disappearance of the variety of life forms present in an ecosystem, region, or on Earth as a whole.

• Loss of biodiversity can disturb ecosystem balance and may lead to the extinction of species.
• Extinction may occur naturally over long periods, during mass extinction events, or as a result of human activities.

Types of extinction

The present biodiversity crisis is often described as an ongoing mass extinction driven mainly by human activities, with extinction rates estimated to be around 100 to 1000 times higher than earlier natural rates.

The four major causes of biodiversity loss are commonly grouped as the Evil Quartet.

Human causes

• Habitat destruction due to development, agriculture, and deforestation is a major driver of biodiversity decline.
• Hunting and over-exploitation reduce populations faster than they can recover.
• Invasive alien species spread rapidly because they may lack natural predators in the new habitat.

Natural causes

• Natural disasters such as forest fires and earthquakes can also cause biodiversity loss.
• However, the present-day large-scale decline in biodiversity is mainly linked to human activity.

Ecological effects

• Reduced biodiversity lowers plant productivity in ecosystems.
• It disturbs environmental processes such as nutrient cycling, species interactions, and ecosystem functioning.
• Ecosystems with fewer species often show lower resistance to disturbances such as climate variation or disease spread.

• Biodiversity loss involves the decline or complete disappearance of life forms, which severely disrupts ecosystem balance and drives species toward extinction.
• The current global biodiversity crisis is an ongoing, human-driven mass extinction event, with rates accelerating 100 to 1,000 times faster than historical natural background rates.
• Modern species loss is primarily caused by the "Evil Quartet": Habitat Loss and Fragmentation, Over-exploitation, Alien Species Invasion, and Co-extinction.
• Human activities like deforestation shrink natural habitats, while introduced alien species multiply rapidly without natural predators and outcompete indigenous wildlife.
• Reduced ecosystem biodiversity directly leads to lower plant productivity, altered nutrient cycling, and significantly decreased resistance to climate variations and diseases.
• The IUCN Red List systematically tracks these threats by grading species' extinction risks across defined categories, ranging from Least Concern (LC) to Critically Endangered (CR) and Extinct (EX).