Environment & Ecology – NDA Geography Notes

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 scientists are still working to understand. This chapter covers that living system: how it works, how human activity affects it, and what international efforts protect it.

NDA tests this chapter through questions on greenhouse gases, acid rain, biodiversity conventions, and sustainable development concepts. These questions reward clear understanding over memorisation: the concepts connect logically.

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The Environment and the Biosphere

The environment is everything that surrounds and affects a living organism: air, water, soil, temperature, other organisms, and physical and chemical conditions.

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

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

The biosphere is the zone of the Earth where life exists: from the deepest ocean trenches to the highest mountain peaks. It is organised as:

Organism → Population → Community → Ecosystem → Biosphere

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

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Ecosystems and Trophic Levels

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

Energy enters most ecosystems through photosynthesis: plants capture sunlight and convert it to chemical energy. This energy passes through trophic levels:

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

Primary consumers (Herbivores): animals that eat producers. Primary consumers are NOT autotrophs: they are heterotrophs.

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 soil. Decomposers are called saprotrophs.

At each trophic level transfer, about 90% of energy is lost as heat: only 10% passes to the next level. This is why food chains rarely exceed four or five links.

Most of the world’s biomass is in the oceans: primarily as phytoplankton.

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The Carbon Cycle

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

Carbon enters the living world through photosynthesis: plants absorb CO₂ from the atmosphere. It returns through respiration, decomposition, and combustion.

Human activities: burning fossil fuels and deforestation: add CO₂ to the atmosphere far faster than natural processes can absorb it.

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Greenhouse Effect and Global Warming

The Natural Greenhouse Effect

The natural greenhouse effect is essential for life. Without it, 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 absorb this outgoing radiation and radiate some back toward the surface: keeping Earth warm.

The role of a greenhouse gas –  let incoming short-wave solar radiation pass through, but block outgoing long-wave infrared radiation.

Carbon dioxide absorbs infrared radiation: this is what makes it a greenhouse gas.

How a glass greenhouse building works: same mechanism: short-wave radiation enters through glass; long-wave radiation from the warm interior cannot exit; heat is trapped.

Greenhouse Gases

Gas	Sources	Key Fact
Carbon dioxide (CO₂)	Burning fossil fuels; deforestation	Absorbs infrared radiation
Methane (CH₄)	Wetlands; livestock; rice paddies; landfills	Wetlands –  largest natural source
Nitrous oxide (N₂O)	Agriculture; fertilisers; burning fossil fuels	—
CFCs	Refrigerants; aerosols	Longest atmospheric residence time; also destroy ozone
Water vapour	Evaporation	Most abundant GHG; not directly emitted by humans
Ozone (O₃)	Ground-level; photochemical reactions	Pollutant at ground level

CFCs have the longest atmospheric residence time among greenhouse gases: some last over 100 years.

Biogas consists mainly of methane and carbon dioxide.

Global Warming Effects

• Rise in sea levels from melting of ice sheets on land (Greenland, Antarctica): NOT from melting icebergs. Icebergs are already floating: their melting does not significantly raise sea levels.
• Increase in extreme weather events
• Shift in agricultural zones
• Loss of biodiversity
• New shipping routes as Arctic ice melts

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Acid Rain

Normal rainwater has pH approximately 5.6 (slightly acidic due to dissolved CO₂ forming carbonic acid). When pH falls below 5.6, it is called acid rain.

Causes of acid rain: Emissions of sulphur dioxide (SO₂) and oxides of nitrogen (NOₓ) from burning coal, vehicle exhaust, and industrial processes. These react with water, oxygen, and other chemicals to form sulphuric acid and nitric acid: which fall with rain.

Carbon dioxide alone does NOT cause acid rain: it only forms mild carbonic acid. Acid rain requires SO₂ and NOₓ.

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.

Eutrophication is NOT a measure to control pollution: it IS itself a form of water pollution (excess nutrients from fertiliser runoff causing algae blooms that deplete oxygen and kill aquatic life).

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Ozone Depletion

• The ozone layer in the stratosphere (15–35 km) absorbs harmful UV radiation
• CFCs rise to the 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

Biodiversity is the variability among living organisms from all sources: including terrestrial, marine, and other ecosystems: encompassing 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

Biodiversity is highest in tropical regions: particularly tropical rainforests. Over 50% of the world’s animal species are found in tropical rainforests.

Endemic species: species confined to a particular region and found nowhere else in the world. The Nilgiri tahr is endemic to the Nilgiri Hills.

IUCN Red List categories (most to least threatened):

Extinct → Extinct in Wild → Critically Endangered → Endangered → Vulnerable → Near Threatened → Least Concern

Red Sanders (Red Sandalwood) has been categorised as Endangered by IUCN.

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Biodiversity Hotspots and Threats

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. India has three biodiversity hotspots: Western Ghats and Sri Lanka | Eastern Himalayas (Indo-Burma) | Sundaland (Andaman and Nicobar Islands).

Major causes of biodiversity loss: Large-scale deforestation | exploitation of forest produce | encroachment in forest areas | pollution | invasive species | climate change.

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.

Afforestation helps groundwater recharge: it does NOT deplete groundwater. Loss of forests, excessive pumping, and large-scale concrete construction all deplete groundwater.

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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.

Biosphere Reserves:

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. India has 18 designated Biosphere Reserves: the first was the Nilgiri Biosphere Reserve (established 1986). NOT all 18 are included in the UNESCO World Network.

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International Environmental Agreements

★ IMPORTANT The most common NDA trap: Montreal Protocol –  ozone layer (NOT climate change). Kyoto Protocol –  greenhouse gas emissions. Students repeatedly confuse these two.

Agreement	Year	Subject	Key Detail
Brundtland Report	1987	Sustainable development definition	“Meets present needs without compromising future generations”
Montreal Protocol	1987	Ozone layer: phase out CFCs	NOT about climate change
Rio Earth Summit (UNCED)	1992	Broad environmental agenda	Agenda 21; CBD; UNFCCC
Kyoto Protocol	1997	Greenhouse gas emission reduction	Committed developed countries below 1990 levels
Paris Agreement	2015	Climate change: temperature target	Well below 2°C; NDCs (Nationally Determined Contributions)
SDGs	2015	17 goals; 2015–2030	No poverty, zero hunger, climate action, etc.
Ramsar Convention	1971	Wetland preservation	Signed in Ramsar, Iran; Ramsar sites –  listed wetlands
Convention on Biological Diversity (CBD)	1992	Biodiversity conservation	Rio Earth Summit outcome

Brundtland definition of sustainable development (1987): “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

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Sustainable Development

Three pillars: Economic (growth creating wealth) | Environmental (protecting natural resources) | 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 – collection + separation + processing + manufacture of new products from waste materials. Reduces waste disposal costs.

Xeriscaping – landscaping that saves water: using drought-resistant plants and efficient watering.

Global Dimming – gradual reduction in sunlight reaching Earth’s surface: caused by increased aerosols and particles from pollution.Soil – exhaustible but renewable natural resource: it can be depleted but restored through proper management. Solar energy is inexhaustible.

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