Environmental and ecological change and impact assessment

1 Introduction to Ecosystem – Structure (Biotic and Abiotic Components)

An ecosystem is a natural unit in which all living organisms (plants, animals, microorganisms) in an area interact continuously with each other and with their physical environment (air, water, soil, temperature) to form a balanced system. The term was first proposed by British botanist Arthur Tansley in 1935. A pond, a forest, a desert, even a small garden in your home—all are examples of ecosystems.

Two main components of an ecosystem

2 Functions of ecosystem – food chain, food web and energy flow

Energy in an ecosystem flows in one direction—from the sun to producers, then to various categories of consumers—while nutrients are recycled in a cyclical manner. This energy-transfer pathway is called a food chain.

In real nature, organisms aren't part of just one food chain—many food chains interconnect to form a complex network called a food web. This network makes ecosystems more stable and resilient—if one food source is depleted, organisms can switch to another.

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Energy flow – from the sun through producers, herbivores, carnivores and decomposers and back to mineral nutrient reserves

10% Law

According to this law, formulated by ecologist Raymond Lindeman, on average only 10% of energy is transferred from one trophic level of a food chain to the next—the remaining 90% is lost through respiration, movement, and heat. This is why food chains usually have no more than 4–5 trophic levels, and the population of top predators (e.g., tigers, eagles) is always much smaller than that of producers.

3 Types of ecosystems – terrestrial and aquatic

Ecosystems on Earth are broadly divided into two categories—terrestrial and aquatic, which are further divided into several subtypes.

4 Biogeochemical cycles – carbon, nitrogen and water cycles

Biogeochemical cycles are the natural processes by which essential elements on Earth (carbon, nitrogen, water, etc.) are continuously cycled between living organisms, the atmosphere, the hydrosphere, and the lithosphere—these cycles make life possible indefinitely, because matter is not destroyed, but merely transformed and transferred from one form to another.

Carbon Cycle

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🖼️ Global carbon cycle — flow of carbon (in gigatons) between the atmosphere, vegetation, soil, oceans, and fossil fuel reserves

During photosynthesis, plants absorb carbon dioxide (CO₂) from the atmosphere and convert it into organic compounds; this carbon is returned to the atmosphere as CO₂ during respiration, combustion (burning fossil fuels), and decomposition. Since the Industrial Revolution, human activities (combustion of coal, petrol, and natural gas) have significantly disrupted this cycle—more carbon is being emitted into the atmosphere than can be naturally absorbed, which is the root cause of climate change (detailed in the next topic).

Nitrogen Cycle – A Brief Review

About 78% of the atmosphere is nitrogen gas, but most organisms cannot use it directly. Biological nitrogen-fixing bacteria such as Rhizobium (see Chapter 9) convert it into a form usable by plants, which moves through the food chain, and is eventually returned to the atmosphere through decomposition and denitrification.

Water Cycle – A Brief Review

The sun's heat evaporates water from oceans, rivers, and lakes, forming clouds that return to the earth as rain—this water returns to groundwater, rivers, and then the oceans, completing the cycle. For an arid state like Rajasthan, any disruption to the water cycle (such as erratic rainfall patterns) has a direct and serious impact on water security (detailed in Topic 13).

5 Climate Change – Causes and Greenhouse Effect

The greenhouse effect is essentially a natural and life-supporting process—if it weren't there, the Earth's average temperature would be around -18°C, too cold for life. Certain gases in the atmosphere (carbon dioxide, methane, nitrous oxide, water vapor) partially trap heat from the Sun from escaping into space, keeping the Earth's temperature habitable (about 15°C on average)—much like a glass greenhouse prevents heat from escaping.

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🖼️ Greenhouse gases keep the Earth's surface warm by redirecting long-wave radiation — without greenhouse gases, the temperature would be -18°C, currently 15°C

6 Climate Change – Global and Indian Impacts

The impact of climate change is no longer just a future concern, but a present reality – its effects are clearly visible globally and in India.

Global impact

• Temperature rise: The Earth's average temperature has risen by about 1.1–1.2°C since the Industrial Revolution, and at the current pace it could rise by 2.5–3°C by 2100.
• Melting glaciers and sea level rise: Polar ice and mountain glaciers (such as the Himalayas) are melting rapidly, causing sea levels to rise and increasing the risk of coastal areas and island nations being submerged.
• Extreme weather events: More frequent and intense cyclones, droughts, floods and heat waves.
• Biodiversity loss: Many species are facing the threat of extinction due to changing temperatures and habitat loss.

Impact on India

• Monsoon vagaries: Unpredictable changes in rainfall patterns—extreme floods, prolonged droughts.
• Melting Himalayan glaciers: Water sources of major rivers like Ganga, Yamuna, Brahmaputra in danger.
• Threat to coastal areas: Coastal metropolises like Mumbai, Chennai, Kolkata may be affected by sea-level rise.
• Impact on agriculture: Irregular monsoons and rising temperatures affect crop productivity, especially in rain-fed agricultural areas.

7 Air pollution – sources, effects and control

Air pollution refers to the presence of harmful substances (gases, dust particles) in the atmosphere that are detrimental to human health, vegetation, and the environment. Many Indian cities are among the most polluted in the world, with air quality in northern India reaching severe levels, especially during winter.

Air pollution control measures

• Promotion of clean energy sources (solar, wind); BS-VI emission standards for vehicles and promotion of electric vehicles.
• National Clean Air Programme (NCAP): Launched in 2019, aims to reduce PM concentrations by 40% by 2026.
• Strict enforcement of industrial emission standards and expansion of air quality monitoring system (AQI).

8 Water and soil pollution

Water pollution and soil pollution are serious problems affecting two other important components of the ecosystem – water and land – which have a direct impact on food security and human health (see Chapters 7 and 8).

Major sources of water pollution

• Industrial Effluents: Chemical waste from factories released directly into rivers without treatment.
• Domestic sewage: Untreated sewage from urban areas flowing into rivers and lakes – most of India's major rivers (including the Ganga and Yamuna) are affected by this.
• Agricultural Runoff: Excessive use of chemical fertilizers and pesticides, which flow into water sources with rainwater – this causes eutrophication (uncontrolled growth of algae due to excess nutrients and lack of oxygen).

Major sources of soil pollution

• Excessive use of chemical fertilizers and pesticides – damages the natural fertility and microbial diversity of the soil.
• Unsafe disposal of industrial and mining waste – accumulation of heavy metals (lead, cadmium, mercury) in the soil.
• Plastic waste – which takes hundreds of years to decompose naturally – affects the water-holding capacity and fertility of the soil.

9 Environmental Impact Assessment (EIA) – Process and Importance

Environmental Impact Assessment (EIA) is a scientific and regulatory process that assesses the potential impact of a major development project (such as a dam, highway, industrial unit, mining) on ​​the environment, biodiversity, and local communities before granting permission, in order to strike a balance between development and environmental protection.

10 India's Environmental Policy and Legal Framework

India has developed a comprehensive legal and institutional framework for environmental protection, which has been strengthened from time to time in response to changing challenges.

11 Global environmental agreements – Paris Agreement and COP conference

Climate change is a global challenge that cannot be solved by the efforts of any one country – that is why several international climate agreements have been reached under the leadership of the United Nations.

Major global agreements

• Kyoto Protocol (1997): The first global agreement to set legally binding emissions reduction targets for developed countries.
• Paris Agreement (2015): Aims to limit global temperature rise to well below 2°C above pre-industrial levels, preferably 1.5°C – each country sets its own Nationally Determined Contributions (NDCs).
• COP (Conference of Parties): An annual global conference held under the United Nations Framework Convention on Climate Change (UNFCCC) where decisions on climate policy are made.

12 Desertification – Global and Indian Perspectives

Desertification is the process by which the productive capacity of arid, semi-arid, and sub-humid lands gradually declines due to climate change and human activities (overgrazing, deforestation, unbalanced irrigation, inappropriate agricultural practices), eventually turning the land into a desert-like barren state. This is distinct from the 'expansion' of actual desert across a landmass—it is the gradual erosion of existing fertile land.

13 Environmental challenges of Rajasthan – desertification, water crisis and air pollution

Rajasthan, India's largest state (by area), faces some of the country's most severe environmental challenges due to its unique geographical location—about 60% of the state's land area lies within the Thar Desert, making it one of the most densely populated deserts in the world.

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🖼️ Thar Desert of Rajasthan – sand dunes and vegetation lines coexist, showing the dynamic process of desertification and land use change

Current status of desertification (latest data)

• A positive sign: Rajasthan is the only state in the drylands to have recorded a reduction of about 387,000 hectares in the area of ​​land degradation since 2003-05 – a major reason for this is the gradual conversion of sandy lands to crop-production systems.
• Yet concerns remain: About 20.53% of the state's land area is found to be moderately, 11.67% highly and 6.65% extremely vulnerable to desertification – this vulnerability is particularly high in the southern and eastern parts of the state.
• Wind erosion is the biggest cause of land degradation in western Rajasthan, accounting for about 56% of the total land eroded there.
• Interesting changes: Rainfall patterns in western Rajasthan have changed in recent years—with some arid areas experiencing unusually high rainfall and increased flooding, reflecting the complex and sometimes contradictory impacts of climate change.

Water crisis

Rajasthan is India's most water-scarce state—it covers approximately 10.4% of the country's total geographical area, but has only 1.16% of the country's total water resources. Overexploitation of groundwater (especially for irrigation) has led to dangerously low groundwater levels in many districts of the state.

air pollution

Major cities in Rajasthan, such as Jaipur, Jodhpur, and Kota, are also affected by vehicle emissions, construction activities, and industrial pollution—deteriorating air quality, especially in winter. Natural dust storms in desert regions pose an additional challenge.

14 Rajasthan's environmental conservation efforts and solutions

Despite these serious challenges, Rajasthan has developed several effective environmental conservation models by combining centuries-old traditional knowledge and modern technology, which are appreciated at the national and international levels.

traditional water conservation systems

• Johad: A traditional rainwater harvesting structure in Rajasthan—small earthen dams that store rainwater and raise groundwater levels. Through the efforts of Rajendra Singh (known as the "Water Man") and the Tarun Bharat Sangh, hundreds of johads in the Alwar region were revived, restoring many dying rivers (such as the Arvari).
• Stepwell and Tanka: Underground water storage structures that have been used for centuries to collect rainwater in arid regions.
• Oran: Sacred village forest land, which is community-owned – a unique Rajasthani model of traditional 'community forest conservation', which plays an important role in biodiversity conservation.

Modern conservation initiatives

• Aravalli Green Wall Project: An ambitious project to combat desertification by carrying out large-scale tree plantation in the degraded parts of the Aravalli mountain range, inspired by the famous 'Great Green Wall' of Africa.
• Solar and wind energy expansion: Rajasthan, with its abundant sunshine and open desert terrain, has become one of India's largest solar energy producers—the Bhadla Solar Park (Jodhpur) is among the largest solar parks in the world. This clean energy expansion directly contributes to climate change mitigation.
• Desert Development Programme: A joint initiative of the Central and State Governments, which promotes sustainable development, pasture management and soil conservation in desert districts.
• Social Forestry Schemes of Forest Department Rajasthan: Tree Plantation and Forest Conservation Programmes with the participation of rural communities.