Biodiversity and Conservation

Written and reviewed by Subhra Gupta, Humanities faculty at UniDrill (M.A. Sociology, University of Delhi · 7 years teaching Humanities). Based on NCERT Geography Class XI (Fundamentals of Physical Geography), Chapter 14.

Where is life richest, and who lives there?

Here is a puzzle in two numbers. The tropical rain forests hold about half of all the species on Earth. The tropical regions, which cover only about one fourth of the world's area, also hold about three fourths of the world's human population. The places richest in life are the places where the most people need food, fuel and land. That tension is the whole story of this chapter: what biodiversity is, why it matters, why it is shrinking, and what the world has agreed to do about it.

Why the tropics are richer

Biodiversity depends on vegetation, and vegetation depends on soil, and soil depends on weathering. The weathering mantle (the layer of broken-down rock) is the basis of diverse vegetation and therefore of biodiversity. What drives the weathering is the input of solar energy and water. So areas rich in sunshine and water have a deep weathering mantle, lush and varied vegetation and a wide spectrum of biodiversity. That is why biodiversity is consistently richer in the tropics. As you move towards the poles, you find larger populations of fewer and fewer species.

What is biodiversity?

The word joins bio (life) and diversity (variety). Biodiversity is the number and variety of organisms found within a specified geographic region. It covers the variety of plants, animals and micro organisms, the genes they contain and the ecosystems they form. It includes variability within species, between species and between ecosystems.

Some numbers help to place it in time and scale.

Beyond the textbook. For the exam: the number of species is placed between 2 million and 100 million, with 10 million as the best estimate. In reality: only about 2 million species have been formally named and described, so most species on Earth have not yet been catalogued, and the estimates rest on sampling. Why it matters: it explains why the textbook gives a range and not a single figure.

Three levels of biodiversity

Biodiversity can be discussed at three levels, each answering a different question.

Ecosystem boundaries are hard to draw, because the limits of communities and ecosystems are not rigid. That makes demarcation difficult and complex.

Pause and predict: which level of diversity is shown by (a) many varieties of one crop, (b) forest, grassland and wetland in one region, and (c) the number of bird species in a park?

Check your answer: (a) is genetic diversity, since the variation is within one species. (b) is ecosystem diversity, since different ecosystems are involved. (c) is species diversity, since it counts the different species in an area.

Why biodiversity matters

Biodiversity has helped human culture develop, and human communities have in turn shaped nature at genetic, species and ecological levels. It plays ecological, economic and scientific roles.

Why variety brings stability. Nothing in an ecosystem exists without a reason: every organism takes what it needs and contributes something useful to others. The more diverse an ecosystem, the better the chances that its species will survive adversity and attack, and the more productive it will be. Loss of species reduces the system's ability to maintain itself. Just as a species with high genetic diversity can adapt better to change, an ecosystem with high biodiversity has a better chance of adapting. The more variety of species in an ecosystem, the more stable it is likely to be.

Two views. For the exam: biodiversity has an economic value as a source of resources and an ethical value, since every species has an intrinsic right to exist and it is morally wrong to cause extinction deliberately. Another reading: conservation thinkers often separate the usefulness of nature to people from the value nature has in itself, and debate which should guide policy. The textbook notes that treating biodiversity as a resource to be drawn upon can itself harm it, and that it creates conflicts over how natural resources are divided and appropriated.

Loss of biodiversity

Human population growth has raised the consumption of natural resources and speeded up the loss of species and habitats. Over exploitation and deforestation are rampant to meet the needs of large populations. Because tropical rain forests contain 50 per cent of the species on Earth, destroying them is disastrous for the whole biosphere.

An example of the exotic species problem is the Hawaiian Islands, which have many unique plants and animals that are threatened by introduced species and land development.

Pause and predict: why is a forest hit by a new species brought from another continent often hurt more than a forest hit by a storm?

Check your answer: a storm is a natural disturbance that native species have evolved with. An exotic species is new to the system, so native species may have no defence against it, and the natural biotic community can suffer extensive damage.

Threatened species: the IUCN categories

The International Union for Conservation of Nature and Natural Resources (IUCN) has classified the threatened species of plants and animals into three categories for the purpose of conservation. The IUCN publishes information about endangered species worldwide as the Red List of threatened species.

Beyond the textbook. For the exam: the IUCN's three categories are endangered, vulnerable and rare. In reality: the current IUCN Red List uses a finer scale that includes Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened and Least Concern, and classifies species mainly on population size, rate of decline and range. Why it matters: if a question asks about the current Red List categories, use the finer scale, but for the textbook question the three above are the answer.

Conserving biodiversity

All forms of life are closely interlinked, so disturbance in one gives rise to imbalance in others. If species of plants and animals become endangered, the environment degrades, which may threaten human existence. Conservation therefore needs community involvement, and local institutions are needed. The textbook stresses that the critical problem is not merely conserving species or habitats but continuing the process of conservation.

The world conservation strategy suggests six steps.

The Wild Life (Protection) Act of 1972 and the biosphere reserves it supports are the main national tools in the chapter. National parks, sanctuaries and biosphere reserves are described in detail in the Class XI book on India's physical environment.

Mega diversity countries and hotspots

Some countries in the tropics hold a large share of the world's species diversity. They are called mega diversity centres. There are 12 such countries.

Hotspots are areas rich in species diversity that are also highly vulnerable. They are defined according to their vegetation, because plants determine the primary productivity of an ecosystem. Most, but not all, hotspots depend on species rich ecosystems for food, firewood, cropland and income from timber. Their problems vary: in Madagascar, about 85 per cent of the plants and animals are found nowhere else in the world, and in Hawaii unique species are threatened by introduced species and land development.

Beyond the textbook. For the exam: the IUCN identified biodiversity hotspots, defined by their vegetation. In reality: the hotspot idea was first put forward by the ecologist Norman Myers and is applied today by the organisation Conservation International. A region is a hotspot if it has at least 1,500 species of endemic vascular plants and has lost at least 70 per cent of its original natural vegetation. India includes parts of four hotspots: the Himalaya, the Indo-Burma region, the Western Ghats and Sri Lanka, and Sundaland. Why it matters: it explains why hotspots are chosen for both richness and urgent threat.

Exam traps

60-second revision

Where this chapter connects

• Previous: Movements of Ocean Water ends the water chapters; this chapter turns from the physical environment to the life it supports.
• Related: Natural Vegetation describes the forests and grasslands whose variety is the subject here, and Geomorphic Processes explains the weathering that builds the soil base for vegetation.
• Class XII link: Geographical Perspective on Selected Issues and Problems studies environmental pollution and land degradation, which are among the pressures on biodiversity.