🦋 Chapter 02 · Topic 04 · Threats to Biodiversity

Threats to Biodiversity — HIPPO Framework

The five major threats to biodiversity, invasive species in India, the Sixth Mass Extinction, and climate change impacts for UPSC & PSC exams.

The HIPPO Framework

The HIPPO framework, popularised by E.O. Wilson, identifies the five primary drivers of biodiversity loss in order of their overall impact:

Habitat Loss & Degradation — The #1 Threat

Destruction, fragmentation, or degradation of natural habitats. Caused by deforestation, agricultural expansion, urbanisation, mining, and infrastructure development. Affects more species than any other threat.

Invasive Species

Non-native species introduced (intentionally or accidentally) that outcompete, prey upon, or displace native species. Second most important cause of biodiversity loss globally.

Pollution

Chemical pollution (pesticides, heavy metals, industrial effluents), plastic pollution, noise pollution, and light pollution degrade habitats and directly harm organisms.

Population Growth (Human)

Growing human population increases demand for land, water, food, and energy — driving overexploitation of natural resources and habitat conversion.

Overexploitation

Unsustainable harvesting of species through hunting, poaching, overfishing, and collection for trade. Directly reduces population sizes below viable levels.

⚡ Exam Tip: Habitat loss is the single most important cause of biodiversity loss — always rank it first. Some sources add Climate Change as a 6th threat, making it “HIPPO-C” or simply noting it as an emerging threat.

Habitat Loss in Detail

Deforestation: India loses significant forest cover annually to agriculture, logging, and development
Habitat fragmentation: Large continuous habitats broken into smaller isolated patches — reduces gene flow and increases extinction risk
Edge effects: Fragmented patches have more “edge” relative to interior — edge habitats are more disturbed and support fewer interior-specialist species
Minimum Viable Population (MVP): The smallest population size that can persist in the wild without significant risk of extinction — fragmentation pushes populations below MVP
Wildlife corridors: Strips of habitat connecting fragmented patches — critical for maintaining gene flow (e.g., Elephant corridors in India)

🌿 India’s Forest Cover: According to India State of Forest Report (ISFR) 2021, India’s total forest and tree cover is 80.9 million hectares — 24.62% of geographic area. While this shows slight increase, quality of forests (dense vs. open) matters more than quantity.

Invasive Species in India

Invasive alien species (IAS) are among the most serious threats to India’s biodiversity, particularly in protected areas:

Invasive Species	Type	Impact in India	Affected Region
Lantana camara	Shrub (from Central America)	Invades forest understory; reduces native plant diversity; toxic to livestock	Across India’s forests, especially tiger reserves
Water Hyacinth (Eichhornia crassipes)	Aquatic plant (from South America)	Chokes water bodies; depletes oxygen; kills fish; blocks navigation	Kerala backwaters, Loktak Lake, Chilika Lake
Parthenium hysterophorus	Weed (from Mexico)	Allelopathic — suppresses native plants; causes allergies in humans and animals	Roadsides, agricultural fields across India
Prosopis juliflora (Vilayati Babool)	Tree (from Americas)	Invades grasslands; reduces water table; displaces native vegetation	Rajasthan, Gujarat, Deccan grasslands
Mikania micrantha (Mile-a-minute)	Vine (from South America)	Smothers native vegetation; major threat in NE India and Western Ghats	NE India, Western Ghats

The Sixth Mass Extinction

Earth has experienced five major mass extinctions in its history (the most recent being the K-Pg event 66 million years ago that wiped out non-avian dinosaurs). Scientists now warn we are in the midst of a Sixth Mass Extinction — the Holocene Extinction — driven entirely by human activities.

Current extinction rate is estimated at 1,000 times the natural background rate
Some estimates suggest up to 1 million species are currently threatened with extinction (IPBES 2019)
Unlike previous mass extinctions, this one is driven by a single species — Homo sapiens
Vertebrate populations have declined by an average of 68% since 1970 (WWF Living Planet Report 2020)
The term “biological annihilation” has been used by scientists to describe the scale of current losses

⚡ Key Fact: The current extinction rate is 1,000× the background rate — this is a frequently tested statistic. Some sources cite 100–1,000× depending on the taxa studied.

Climate Change as an Emerging Threat

Climate change is rapidly becoming one of the most significant drivers of biodiversity loss, interacting with and amplifying all other HIPPO threats:

Coral bleaching: Rising sea temperatures cause corals to expel symbiotic algae (zooxanthellae), leading to bleaching and death. India’s Lakshadweep and Andaman reefs are severely affected
Range shifts: Species moving poleward or to higher altitudes as temperatures rise — some cannot move fast enough
Phenological mismatch: Timing of biological events (flowering, migration, breeding) shifts out of sync with food availability or pollinator presence
Sea level rise: Threatens coastal and island ecosystems — mangroves, coral reefs, nesting beaches
Glacial retreat: Threatens Himalayan biodiversity and downstream freshwater ecosystems

Revision Checklist

✅ HIPPO: Habitat loss → Invasive species → Pollution → Population → Overexploitation
✅ Habitat loss = #1 threat to biodiversity globally
✅ Fragmentation → edge effects → reduced gene flow → below MVP
✅ Lantana camara: forest understory invader; toxic to livestock
✅ Water hyacinth: Kerala backwaters, Loktak Lake; depletes oxygen
✅ Parthenium: allelopathic weed; causes allergies
✅ Sixth Mass Extinction = Holocene Extinction; driven by humans
✅ Current extinction rate = 1,000× background rate
✅ ~1 million species threatened (IPBES 2019)
✅ Climate change: coral bleaching, range shifts, phenological mismatch

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