Biodiversity and Conservation

What this chapter is about

Biodiversity refers to the variety of living organisms found on Earth at all levels of biological organisation. This chapter introduces the concept of biodiversity, its measurement, the patterns it shows across the planet, and why it matters for ecosystem functioning and human survival. A Class 12 student encounters this topic because understanding life's diversity is essential for appreciating ecological balance and the urgent need to protect it.

The chapter covers the three levels of biodiversity (genetic, species and ecological), explains how species richness varies with area and latitude, and discusses the causes of biodiversity loss. It also examines different strategies for conservation, including in-situ methods like protected areas and ex-situ methods like seed banks and zoos. After studying this chapter, a student should be able to define biodiversity, explain its importance, analyse threats to it, and suggest scientifically sound conservation measures.

Conservation biology applies ecological principles to preserve species and habitats. India, recognised as one of the world's mega-biodiversity countries, provides numerous examples of both threats and successful conservation efforts that make this chapter directly relevant to Indian students.

Key ideas

• Biodiversity is the totality of genes, species and ecosystems in a region; it can be measured at genetic, species and ecosystem levels.
• Species-Area relationship: The number of species (S) in a region increases with area (A) according to S = cA^z, where c is a constant for the taxonomic group and z typically lies between 0.1 and 0.35 for smaller areas but may approach 0.6–1.2 for very large continental areas.
• Latitudinal gradient: Species richness generally increases from the poles towards the tropics; tropical rainforests hold the highest diversity due to greater solar energy, stable climate and longer evolutionary time.
• Biodiversity loss is driven primarily by habitat destruction, over-exploitation, alien species invasions, and co-extinctions that follow when one species disappears.
• Importance of biodiversity: Ecosystems with higher diversity show greater productivity, better resistance to disturbance, and faster recovery; biodiversity also provides direct economic value (food, medicine, timber) and indirect ecological services (pollination, nutrient cycling).
• In-situ conservation protects species in their natural habitat through national parks, wildlife sanctuaries, biosphere reserves and sacred groves.
• Ex-situ conservation safeguards species outside their habitat in zoos, botanical gardens, gene banks and cryopreservation facilities.
• The Convention on Biological Diversity (CBD), adopted in 1992, commits nations to conserve biodiversity, use it sustainably, and share benefits equitably.

Formulas and facts to remember

1. Species-Area equation: S = cA^z, where S = species richness, A = area, c = y-intercept constant, z = slope (regression coefficient).
2. Typical z-value for islands or small regions: 0.1–0.35; for entire continents: may exceed 0.6.
3. Mega-diversity nations: 12 countries, including India, Brazil, Colombia, Indonesia and Australia, together contain about 70 % of the world's species.
4. India has about 45 000 plant species and over 91 000 animal species described so far; it is one of 17 mega-biodiversity countries.
5. Hotspots: Regions with exceptionally high endemism and serious habitat loss; India lies partly in the Western Ghats-Sri Lanka and the Himalaya hotspots.
6. IUCN Red List categories (from highest to lowest threat): Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern.
7. Rivet-popper hypothesis (Paul Ehrlich): Each species in an ecosystem is like a rivet in an aircraft; losing a few may go unnoticed, but continued loss eventually causes collapse.
8. Sacred groves in India (e.g., in Meghalaya, Rajasthan, Maharashtra) are community-protected forest patches that conserve endemic flora and fauna.

Worked examples

Example 1 — Applying the species-area relationship

A survey of beetles in a 10 km² forest patch finds 120 species. If the regression constant z = 0.3 and c = 30, predict the number of beetle species in a 100 km² forest in the same region.

Solution

Step 1: Write the species-area equation. S = cA^z

Step 2: For A = 100 km², substitute values. S = 30 × (100)^0.3

Step 3: Calculate (100)^0.3. 100 = 10², so (100)^0.3 = 10^(2 × 0.3) = 10^0.6 ≈ 3.98

Step 4: Multiply. S = 30 × 3.98 ≈ 119.4

Predicted species richness ≈ 119 species.

Note: The larger area here shows similar richness because the increase follows a logarithmic pattern; a ten-fold area increase raises species count only about 2-fold when z = 0.3.

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Example 2 — Classifying conservation strategies

A wildlife authority plans the following actions for a threatened frog species found only in a single wetland in Kerala: (a) Declare the wetland a wildlife sanctuary. (b) Collect eggs and rear tadpoles in a breeding centre, releasing adults back into the wild. (c) Store frozen sperm samples in a gene bank.

Classify each action as in-situ or ex-situ conservation.

Solution

(a) Wildlife sanctuary — In-situ: the species is protected in its natural habitat.

(b) Captive breeding and release — Ex-situ (breeding centre is outside the natural habitat) combined with reintroduction (returns organisms to the wild).

(c) Cryopreservation in a gene bank — Ex-situ: genetic material is stored outside the natural environment for future use.

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Example 3 — Identifying causes of biodiversity loss

In a coastal district, mangrove forests are cleared for shrimp aquaculture ponds. An exotic shrimp species escapes and competes with native prawns. Local fisherfolk report declining catches of wild fish.

Identify the causes of biodiversity loss operating here.

Solution

1. Habitat destruction: Clearing mangroves removes nursery grounds for many marine species.
2. Alien species invasion: The escaped exotic shrimp competes with native species for food and space.
3. Over-exploitation: Intensive aquaculture and fishing pressure reduce wild fish populations.
4. Co-extinction (potential): Species dependent on mangroves (certain crabs, molluscs, shore birds) may decline as their habitat disappears.

Common mistakes

• Confusing species richness with species diversity → Species richness is the number of species; diversity also considers relative abundance (evenness).
• Thinking a higher z-value always means more species → z describes the rate of increase with area, not the absolute number; c also matters.
• Believing national parks allow all traditional activities → National parks have stricter restrictions than wildlife sanctuaries; limited human activity is permitted.
• Assuming ex-situ conservation alone can save a species → Long-term survival requires habitat restoration and in-situ protection; ex-situ acts as an insurance.
• Treating all introduced species as invasive → Only those that spread aggressively and harm native species are termed invasive; many exotics remain benign.

Quick revision

• Biodiversity = variety of genes + species + ecosystems.
• Species-area relationship: S = cA^z; more area generally means more species, but the rise is not linear.
• Tropics hold the highest species richness; poles the lowest.
• Four main drivers of loss: habitat loss, over-exploitation, invasive aliens, co-extinctions.
• In-situ = protect in natural habitat; ex-situ = conserve outside (zoos, gene banks).
• India is a mega-biodiversity country with two global biodiversity hotspots within its borders.