Environment, Biodiversity & Sustainable Development – NDA Geography Notes

Introduction

The Earth is not just a collection of rocks, water, and air. It is a living system — billions of species interacting with each other and with their physical environment in ways so complex that scientists are still working to understand them. This chapter is about that living system — how it works, how human activity is affecting it, and what international efforts are being made to protect it.

For NDA, this chapter connects geography to environmental science and current affairs. Questions test whether you understand basic concepts — what greenhouse gases do, why acid rain is harmful, what biodiversity means, what conventions like Ramsar and Kyoto are about. These are not complicated ideas — they just need to be understood clearly once.

This chapter also has strong overlap with Biology and General Science sections of NDA — understanding it well helps across multiple subjects.

Understand the Topic

The Environment

The environment is everything that surrounds and affects a living organism — the air, water, soil, temperature, other organisms, and all the physical and chemical conditions of the place where it lives.

The natural environment consists of:

Abiotic components — the non-living parts: air, water, soil, temperature, sunlight, minerals.

Biotic components — the living parts: all plants, animals, fungi, bacteria, and other organisms.

These two components interact constantly. Plants absorb carbon dioxide and release oxygen. Bacteria break down dead organisms and return nutrients to the soil. Animals eat plants and each other, moving energy and matter through the system.

When this system is in balance, it is stable and self-sustaining. When human activities disturb the balance too rapidly, environmental problems arise.

The Biosphere

The biosphere is the zone of the Earth where life exists — from the deepest ocean trenches to the highest mountain peaks, from the soil to the lower atmosphere. It includes all living organisms and the environments they inhabit.

The biosphere is organised into levels:

Organism → Population → Community → Ecosystem → Biosphere

An organism is a single living being. A population is all organisms of one species in an area. A community is all species in an area. An ecosystem is the community plus all abiotic factors. The biosphere is all ecosystems together.

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Ecosystems

An ecosystem is a functional unit of the environment — a community of living organisms interacting with each other and with the physical environment as a system.

Food chains and food webs:

Energy enters most ecosystems through photosynthesis — plants capture sunlight and convert it to chemical energy stored in their tissues. This energy then passes from one organism to another through eating.

The feeding levels in an ecosystem are called trophic levels:

Producers (Autotrophs) — plants and other photosynthetic organisms that make their own food from sunlight.

Primary consumers (Herbivores) — animals that eat producers.

Secondary consumers (Carnivores) — animals that eat herbivores.

Tertiary consumers — animals that eat secondary consumers.

Decomposers (Saprotrophs) — bacteria and fungi that break down dead organic matter and return nutrients to the soil.

Primary consumers are NOT autotrophs. Primary consumers are heterotrophs — they eat other organisms. Autotrophs are the producers (plants) themselves. [NDA tested via CDS]

Decomposers are called saprotrophs — they break down dead organic matter through chemical digestion outside their body and absorb the products. [NDA tested via CDS]

At each transfer from one trophic level to the next, about 90% of energy is lost as heat — only about 10% passes to the next level. This is why food chains rarely have more than four or five links.

Most of the world’s biomass is in the oceans — primarily as phytoplankton. [NDA tested via CDS]

The Carbon Cycle

Carbon is the fundamental building block of all life. It moves continuously between living organisms and the physical environment in the carbon cycle.

Carbon enters the living world through photosynthesis — plants absorb carbon dioxide from the atmosphere. It returns to the atmosphere through respiration, decomposition, and combustion.

The problem today is that human activities — burning fossil fuels and deforestation — are adding carbon dioxide to the atmosphere much faster than natural processes can absorb it.

Greenhouse Effect and Global Warming

The Natural Greenhouse Effect:

The natural greenhouse effect is essential for life. Without it, the Earth’s average temperature would be about –18°C instead of the current +15°C.

How it works: the Sun’s short-wave radiation passes through the atmosphere and heats the Earth’s surface. The surface radiates heat back upward as long-wave (infrared) radiation. Greenhouse gases in the atmosphere absorb this outgoing radiation and radiate some back toward the surface — keeping it warmer than it would otherwise be.

Greenhouse Gases:

The main greenhouse gases are:

• Carbon dioxide (CO₂) — from burning fossil fuels and deforestation
• Methane (CH₄) — from wetlands, livestock, rice paddies, landfills, natural gas leaks
• Nitrous oxide (N₂O) — from agriculture, fertilisers, burning fossil fuels
• Chlorofluorocarbons (CFCs) — from refrigerants and aerosols; also destroy ozone
• Water vapour — most abundant greenhouse gas; not directly emitted by humans
• Ozone (O₃) — at ground level, a pollutant and greenhouse gas

CFCs have the longest atmospheric residence time among greenhouse gases — some can last over 100 years. [NDA tested via CDS]

Sources of methane:

• Wetlands = largest natural source of methane [NDA tested via CDS]
• Livestock (cattle digestion)
• Rice paddies
• Landfills (decomposition of organic waste)
• Natural gas leaks
• Coal mining

Biogas consists mainly of methane and carbon dioxide. [NDA tested via CDS]

Global warming = rise in global surface temperature caused by increased concentration of greenhouse gases. [NDA tested via CDS]

Effects of global warming:

• Rise in sea levels (melting of ice sheets — NOT icebergs)
• Increase in extreme weather events
• Shift in agricultural zones
• Loss of biodiversity
• New shipping routes as Arctic ice melts (may benefit Russia and northern nations)

Long-term sea level rise is caused by melting of ice sheets on land (Greenland, Antarctica) — NOT by melting icebergs. Icebergs are already floating — their melting does not significantly raise sea levels. [NDA tested via CDS]

Greenhouse effect in a glass building:

• Short-wave radiation from the Sun enters through the glass
• Long-wave infrared radiation from ground CANNOT exit through glass
• Heat is trapped inside — same mechanism as atmospheric greenhouse effect [NDA tested via CDS]

Carbon dioxide absorbs infrared radiation — this is what makes it a greenhouse gas. [NDA tested via CDS]

The role of a greenhouse gas is to let incoming sunlight pass through but stop outgoing infrared radiation. [NDA tested via CDS]

Acid Rain

What is acid rain?

Normal rainwater is slightly acidic — pH about 5.6 (due to dissolved CO₂ forming carbonic acid). When the pH falls below 5.6, it is called acid rain. [NDA tested via CDS]

Causes of acid rain:

The main cause is emission of sulphur dioxide (SO₂) and oxides of nitrogen (NOₓ) into the atmosphere — from burning coal and fossil fuels, vehicle exhaust, and industrial processes. These react with water, oxygen, and other chemicals to form sulphuric acid and nitric acid — which fall with rain.

Primary cause = dissolution of sulphur and nitrogen oxides in rain. [NDA tested via CDS]

Carbon dioxide also dissolves in rain but forms only mild carbonic acid — it does NOT make rain acidic enough to cause acid rain damage. Carbon oxides alone do NOT cause acid rain.

Effects of acid rain:

• Dissolves limestone and marble buildings (calcium carbonate reacts with sulphuric acid)
• Acidifies lakes and rivers — kills fish and aquatic life
• Weakens trees and kills soil organisms
• Leaches nutrients from soil

A major environmental issue in eastern Canada is acid precipitation. [NDA tested via CDS]

Eutrophication is NOT a measure to control pollution — it is itself a form of water pollution (excess nutrients causing algae blooms that deplete oxygen). [NDA tested via CDS]

Ozone Depletion

Already covered in Chapter 12 — brief summary:

• Ozone layer in stratosphere absorbs harmful UV radiation
• CFCs rise to stratosphere and destroy ozone molecules
• Ozone hole most pronounced over Antarctica
• Montreal Protocol (1987) = international agreement to phase out ozone-depleting substances
• World Ozone Day = 16 September

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Biodiversity

What is biodiversity?

Biodiversity is the variety of life on Earth at all levels — from genes to ecosystems.

Precise definition: the variability among living organisms from all sources including terrestrial, marine and other ecosystems, and the ecological complexes of which they are part — including diversity within species, between species, and of ecosystems.

Three levels of biodiversity:

• Genetic diversity — variation within a species
• Species diversity — variety of different species in an area
• Ecosystem diversity — variety of different ecosystems

Where is biodiversity highest?

Biodiversity is highest in tropical regions — particularly tropical rainforests. Over 50% of the world’s animal species are found in tropical rain forests. [NDA tested via CDS]

As you move toward the poles, biodiversity decreases.

Endemic species:

An endemic species is one confined to a particular region and found nowhere else in the world. The Nilgiri tahr is endemic to the Nilgiri Hills. [NDA tested via CDS]

Biodiversity Hotspots

A biodiversity hotspot is a region that is:

1. Rich in species — particularly endemic species
2. Highly threatened — having lost at least 70% of its original habitat

The concept was developed by Norman Myers in 1988. [NDA tested via CDS]

Important criteria for identifying hotspots:

• High species richness — particularly endemic species
• High degree of threat to habitat

India has several biodiversity hotspots:

• Western Ghats and Sri Lanka
• Eastern Himalayas (Indo-Burma hotspot)
• Sundaland (Andaman and Nicobar Islands)

Threats to Biodiversity

Major causes of biodiversity loss:

• Large-scale deforestation — destroys habitats
• Exploitation of forest produce — hunting, poaching, over-harvesting
• Encroachment in forest areas — human settlements expanding into forests
• Pollution — degrades habitats
• Invasive species — introduced species outcompeting native species
• Climate change — altering habitats and migration patterns

Sacred groves (forest patches protected by local communities for religious reasons) actually help biodiversity — they serve as refuges for species. Maintaining sacred groves is NOT a cause of biodiversity decrease. [NDA tested via CDS]

Afforestation helps groundwater recharge — it does NOT deplete groundwater. Loss of forests, excessive pumping, and concrete construction all deplete groundwater. [NDA tested via CDS]

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Conservation of Biodiversity

In-situ conservation — conserving species in their natural habitat:

• National parks
• Wildlife sanctuaries
• Biosphere reserves
• Sacred groves

Ex-situ conservation — conserving species outside their natural habitat:

• Zoos
• Botanical gardens
• Seed banks
• Gene banks

IUCN Red List

The IUCN (International Union for Conservation of Nature) publishes the Red List of Threatened Species — a comprehensive inventory of conservation status of species globally.

IUCN Red List categories (from most to least threatened):

• Extinct — no individuals remaining anywhere
• Extinct in Wild — only survives in captivity
• Critically Endangered — extremely high risk of extinction
• Endangered — very high risk of extinction
• Vulnerable — high risk of extinction
• Near Threatened — close to qualifying as threatened
• Least Concern — widespread and abundant

Red Sanders (Red Sandalwood) has been categorised as Endangered by IUCN. [NDA tested via CDS]

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Biosphere Reserves

A biosphere reserve is a special conservation area that integrates conservation with sustainable human use.

Each biosphere reserve has three zones:

• Core zone — strictly protected; no human activity
• Buffer zone — limited research and education
• Transition zone — sustainable development and human settlement

The concept was initiated by UNESCO in 1973–74 under the Man and Biosphere (MAB) Programme. [NDA tested via CDS]

India has 18 designated Biosphere Reserves. The first was the Nilgiri Biosphere Reserve (established 1986). [NDA tested via CDS]

NOT all 18 are included in the UNESCO World Network of Biosphere Reserves. [NDA tested via CDS]

Important International Conventions and Agreements

Agreement	Year	Subject
Brundtland Report	1987	Defined sustainable development
Montreal Protocol	1987	Ozone layer — phase out CFCs
Rio Earth Summit (UNCED)	1992	Agenda 21; CBD; UNFCCC
Kyoto Protocol	1997	Greenhouse gas emission reduction
Paris Agreement	2015	Temperature rise well below 2°C; NDCs
SDGs	2015	17 goals; 2015–2030

Ramsar Convention:

• About: Wetland preservation
• Signed: 1971, in Ramsar, Iran
• Sites listed under Ramsar = Ramsar sites [NDA tested via CDS]

Kyoto Protocol:

• About: Greenhouse gas emission reduction
• Adopted: 1997, Kyoto, Japan
• Based on: UNFCCC
• Committed developed countries to reduce emissions below 1990 levels

Paris Agreement:

• About: Climate change — keeping global temperature rise well below 2°C above pre-industrial levels
• Adopted: 2015, COP-21, Paris
• Each country submits its own targets (NDCs — Nationally Determined Contributions)

Montreal Protocol:

• About: Ozone layer protection — phasing out CFCs
• Signed: 1987, Montreal, Canada

Convention on Biological Diversity (CBD):

• About: Biodiversity conservation
• Adopted: 1992, Rio Earth Summit

Rio Earth Summit (1992):

• Full name: United Nations Conference on Environment and Development (UNCED)
• Location: Rio de Janeiro, Brazil
• Key outcomes: Agenda 21, CBD, UNFCCC

Brundtland Report (1987):
The most famous definition of sustainable development:
“Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” [NDA tested via CDS]

The Montreal Protocol is about ozone layer protection — NOT climate change emission reduction. Students often confuse it with Kyoto Protocol. [NDA tested via CDS]

Sustainable Development

Definition (Brundtland Commission, 1987):
Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Three pillars of sustainable development:

• Economic — growth that creates wealth
• Environmental — protecting natural resources and ecosystems
• Social — equity and human well-being

Sustainable Development Goals (SDGs):

• Adopted: 2015
• Number: 17 goals
• Timeline: 2015–2030
• Examples: No poverty, zero hunger, clean water, climate action, life on land, life below water

Recycling:
Recycling is NOT just the collection and separation of waste — it is the collection, separation, processing, and manufacture of new products from waste materials. Recycling reduces waste disposal costs. [NDA tested via CDS]

Xeriscaping:
Landscaping that saves water — using drought-resistant plants and efficient watering in garden design. [NDA tested via CDS]

Global Dimming:
The gradual reduction in the amount of global direct irradiance (sunlight) reaching the Earth’s surface — caused by increased particles and aerosols from pollution. [NDA tested via CDS]

Soil as a resource:
Soil is classified as an exhaustible but renewable natural resource — it can be depleted but also restored through proper management. Solar energy is inexhaustible. [NDA tested via CDS]

Pollution

Types of Pollution:

Air Pollution:

• Primary pollutants: emitted directly (SO₂, NOₓ, CO, particulates)
• Secondary pollutants: formed by reactions in atmosphere (ground-level ozone, smog)
• Smog: photochemical (formed when pollutants react in sunlight) or London smog (industrial smoke + fog)

Water Pollution:

• Eutrophication — excessive nutrients from fertiliser runoff cause algae to bloom; algae die and decomposition depletes oxygen; kills aquatic life

Methane from Landfills:
Landfills release methane — from decomposition of organic waste. [NDA tested via CDS]

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Coral Bleaching

Coral bleaching occurs when coral polyps experience stress — primarily from warming ocean temperatures. Corals expel the coloured algae (zooxanthellae) living in their tissues, turning white. Without the algae, corals lose their food source and may die.