Extinction

Extinction is the permanent disappearance of a species from Earth. When the last member of a species dies, the species is said to be extinct. Extinction is a natural part of evolution, but in modern times, the rate of extinction has accelerated dramatically due to human activities. In biological terms, extinction is the complete disappearance of a species, with no individuals remaining anywhere on Earth. It marks the end of that species’ evolutionary lineage.

1.0Types of Extinction

Biologists and conservationists recognise several categories or types of extinction:

1. Natural Extinction

This occurs as part of natural evolutionary processes. Species that are unable to adapt to environmental change eventually disappear.
Example: The extinction of dinosaurs due to natural catastrophes like asteroid impacts and volcanic activity.

2. Anthropogenic Extinction

Caused directly or indirectly by human activities, including deforestation, pollution, overhunting, and habitat destruction.
Example: Extinction of the Passenger Pigeon due to large-scale hunting in North America.

3. Mass Extinction

A mass extinction is a sudden, global event causing widespread loss of species across multiple habitats. These events have occurred several times in Earth’s history.

2.0The Five Major Mass Extinctions in Earth’s History

1. Ordovician–Silurian Extinction (≈440 million years ago)
2. • Caused by glaciation and sea-level fall.
   • About 85% of marine species died.
2. Late Devonian Extinction (≈365 million years ago)
3. • Triggered by oceanic changes and asteroid impacts.
   • Affected coral reefs and marine organisms.
3. Permian–Triassic Extinction (≈250 million years ago)
4. • Known as “The Great Dying.”
   • Around 96% of marine species and 70% of land species vanished.
4. Triassic–Jurassic Extinction (≈200 million years ago)
5. • Volcanic eruptions and climate change.
   • Allowed dinosaurs to dominate the Earth.
5. Cretaceous–Paleogene Extinction (≈65 million years ago)
6. • Likely caused by a massive asteroid impact.
   • Ended the reign of dinosaurs, paving the way for mammals.

3.0The Sixth Mass Extinction: Human Impact

Causes and Evidence

Scientists warn that Earth is undergoing a sixth mass extinction, driven by human activities. Species are disappearing at 100–1,000 times the natural rate due to deforestation, climate change, and pollution.

Current Rate of Species Loss

According to the IUCN, over 42,000 species are currently threatened with extinction, including:

• 27% of mammals
• 41% of amphibians
• 34% of conifers

4.0Causes of Extinction

Natural Causes

• Climate Change - Fluctuations in temperature and rainfall can make habitats uninhabitable for certain species.

• Volcanic Activity and Meteor Impacts - Massive eruptions or asteroid impacts can cause sudden environmental shifts, leading to widespread extinction.

• Competition and Evolutionary Pressure - Stronger or more adaptable species often outcompete others, leading to their decline.

Human-Induced Causes

• Deforestation and Habitat Destruction - Clearing forests for agriculture, mining, and urbanisation eliminates habitats and food sources.

• Pollution and Global Warming - Chemical waste, oil spills, and greenhouse gases disrupt ecosystems and threaten marine and terrestrial life.

• Overexploitation and Illegal Wildlife Trade - Unsustainable hunting, fishing, and trade drive many species toward extinction (e.g., rhinos and tigers).

• Invasive Species Introduction - Non-native species introduced intentionally or accidentally disrupt local ecosystems.
  Example: The brown tree snake in Guam wiped out native bird populations.

5.0Preventing Extinction: Conservation Strategies

1. In-situ Conservation

Protecting species within their natural habitats through:

• National Parks
• Wildlife Sanctuaries
• Biosphere Reserves

Example: Kaziranga National Park for the conservation of the one-horned rhinoceros.

2. Ex-situ Conservation

Preserving species outside their natural habitats through:

• Zoos and Botanical Gardens
• Seed Banks and Cryopreservation
• Captive Breeding and Reintroduction Programs

Example: The Arabian Oryx was successfully reintroduced into the wild after captive breeding.

3. Legal and Global Measures

• Wildlife Protection Act (1972) – Protects threatened species in India.
• CITES (Convention on International Trade in Endangered Species) – Controls international trade of endangered species.
• IUCN Red List – Classifies species based on extinction risk levels (e.g., Vulnerable, Endangered, Critically Endangered).

6.0Examples of Extinct Species

7.0Role of Humans in Preventing Extinction

Sustainable Practices

• Support eco-friendly products.
• Avoid illegal wildlife products.
• Promote reforestation and habitat conservation.

Public Awareness and Education

Education fosters appreciation for biodiversity and encourages participation in conservation movements.