Extinction is the permanent disappearance of a species from Earth. It is a natural process that has occurred throughout geological history, as seen in the extinction of dinosaurs about 65 million years ago. However, in the present age, human activities have accelerated extinction rates to alarming levels, far exceeding the natural background rate. The loss of species threatens not only biodiversity but also the ecological balance and resources essential for human survival. The major causes of extinction can be grouped into natural and anthropogenic factors.
1. Habitat Loss and Fragmentation
The most significant cause of species extinction is the destruction of natural habitats. Expanding agriculture, deforestation, mining, urbanization, and infrastructure projects reduce the living space for wildlife. Habitat fragmentation isolates populations, making them more vulnerable to genetic decline and inbreeding. For instance, the fragmentation of tiger habitats in India has led to declining populations and increased human–wildlife conflicts.
2. Overexploitation
Overhunting, overfishing, and overharvesting of plants and animals for food, medicine, timber, and trade have driven many species to extinction. The dodo bird of Mauritius was hunted to extinction in the 17th century. Similarly, excessive hunting of passenger pigeons in North America wiped out the species. In India, species like the Indian bustard and pangolin are critically endangered due to hunting and trade.
3. Pollution
Pollution of air, water, and soil has severely impacted species survival.
- Industrial effluents and sewage degrade aquatic habitats, leading to fish kills and loss of aquatic biodiversity.
- Pesticides and chemicals poison ecosystems, affecting birds and insects (e.g., the decline of vultures in India due to diclofenac poisoning).
- Plastic pollution in oceans entangles marine species like turtles, dolphins, and seabirds.
Pollution not only kills directly but also reduces reproduction and weakens species over time.
4. Climate Change
Global warming and climate change are altering habitats and species distribution. Rising temperatures, melting ice caps, sea-level rise, and shifting rainfall patterns force species to adapt, migrate, or perish. Polar bears are threatened as Arctic ice melts, while coral reefs are bleaching due to ocean warming and acidification. Species with narrow ecological ranges, such as alpine plants, face higher extinction risks as their habitats shrink.
5. Invasive Species
The introduction of non-native species often threatens local biodiversity by outcompeting, preying upon, or spreading diseases among native species. For example, the brown tree snake introduced to Guam caused the extinction of several bird species. In India, invasive weeds like Lantana camara and Eichhornia (water hyacinth) have degraded habitats, pushing native species towards decline.
6. Diseases
Emerging infectious diseases, often linked to human activities and climate change, pose new threats to wildlife. For example, the chytrid fungus has caused the extinction of several amphibian species worldwide. Similarly, rinderpest outbreaks historically wiped out populations of wild ungulates in Africa.
7. Small Population Size and Genetic Factors
Species with small populations face extinction risks due to inbreeding, reduced genetic diversity, and inability to adapt to environmental changes. Such populations are also vulnerable to random events such as natural disasters. The cheetah, for example, has very low genetic diversity, making it highly susceptible to diseases and habitat changes.
Conclusion
The extinction of species is driven by a combination of human-induced and natural factors. Habitat destruction, overexploitation, pollution, climate change, invasive species, diseases, and genetic problems all contribute to biodiversity loss. The rapid rate of extinction in the modern era is largely due to human pressures on ecosystems. Preventing extinction requires global cooperation in habitat conservation, pollution control, sustainable use of resources, and protection of endangered species. Conserving species is not only an ethical responsibility but also essential for maintaining ecological balance and ensuring the survival of humankind.
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