📚 What is Environment & Environmental Science?
The environment is the sum total of all living (biotic) and non-living (abiotic) components that surround and affect an organism. It includes air, water, soil, climate, plants, animals, and human-made structures.
Environmental Science is an interdisciplinary field that combines biology, chemistry, physics, geology, and social sciences to study the environment and find solutions to environmental problems.
Why Study Environmental Science?
- Understanding how nature works and how humans impact it
- Climate change, pollution, deforestation are global crises needing informed citizens
- India's Supreme Court made it mandatory for all undergraduate students (2003)
- Helps make sustainable choices in technology and daily life
📚 Ecosystems — In Complete Detail
An ecosystem is a functional unit of nature where living organisms interact with each other and with their physical environment. The term was coined by A.G. Tansley in 1935.
Components of an Ecosystem:
| Component | Type | Details |
|---|---|---|
| Abiotic (Non-living) | Physical & Chemical factors | Sunlight (energy source for all life), temperature, water, soil, minerals, air, humidity, pH, wind. These determine WHICH organisms can survive. |
| Producers (Autotrophs) | Biotic — make their own food | Plants, algae, phytoplankton. Use photosynthesis: CO₂ + H₂O + Sunlight → Glucose + O₂. They are the foundation of every food chain. |
| Consumers (Heterotrophs) | Biotic — eat other organisms | Primary (herbivores: deer, rabbit), Secondary (small carnivores: frog, snake), Tertiary (top predators: eagle, lion), Omnivores (eat both: bear, human) |
| Decomposers (Saprotrophs) | Biotic — break down dead matter | Bacteria, fungi. They recycle nutrients back into soil, completing the nutrient cycle. Without them, dead matter would pile up endlessly. |
Types of Ecosystems:
| Category | Sub-types | Characteristics |
|---|---|---|
| Terrestrial | Forest, Desert, Grassland, Tundra | Forests: highest biodiversity. Deserts: extreme heat, low water. Tundra: extremely cold, permafrost. |
| Freshwater | Rivers, Lakes, Ponds, Wetlands | Low salt content (<0.5%). Wetlands are "kidneys of Earth" — filter water naturally. |
| Marine | Oceans, Coral Reefs, Estuaries | Covers 71% of Earth. Coral reefs = "rainforests of the sea" (highest marine biodiversity). |
Food Chain — Who eats whom:
Each level is called a Trophic Level:
- T1: Producers (plants) — capture solar energy
- T2: Primary consumers (herbivores) — eat producers
- T3: Secondary consumers (carnivores) — eat herbivores
- T4: Tertiary consumers (top predators) — eat carnivores
Food Web: In reality, animals eat multiple things. Interconnected food chains form a food web (more accurate representation).
10% Rule (Lindeman's Law of Energy Transfer):
Herbivores get: 1,000 kcal (10%)
Small carnivores get: 100 kcal (10% of 1,000)
Top predators get: 10 kcal (10% of 100)
This is why food chains rarely have more than 4-5 levels!
Ecological Pyramids — graphical representation of trophic levels:
| Pyramid Type | What it shows | Shape |
|---|---|---|
| Pyramid of Energy | Energy at each level | Always upright (energy always decreases upward) |
| Pyramid of Numbers | Number of organisms | Usually upright. Can be inverted (1 tree supports many insects) |
| Pyramid of Biomass | Total mass of organisms | Upright in terrestrial. Can be inverted in aquatic (tiny phytoplankton support large fish) |
Biogeochemical Cycles — how elements cycle through ecosystems:
- Carbon Cycle: CO₂ absorbed by plants (photosynthesis) → animals eat plants → respiration releases CO₂ → decomposition releases CO₂ → fossil fuels burn releases CO₂. Human activity is adding TOO MUCH carbon.
- Nitrogen Cycle: N₂ in atmosphere (78%!) → bacteria "fix" it into usable forms → plants absorb → animals eat → decomposition returns to soil → denitrifying bacteria release N₂ back.
- Water Cycle: Evaporation → Condensation (clouds) → Precipitation (rain/snow) → Runoff/Infiltration → back to oceans/groundwater.
📚 Natural Resources
Natural resources are materials and energy found in nature that humans use for survival and development.
| Type | Definition | Examples |
|---|---|---|
| Renewable | Replenished naturally in a short time | Solar, wind, water, biomass, geothermal, tidal |
| Non-renewable | Finite, takes millions of years to form | Coal, petroleum, natural gas, minerals, nuclear fuels |
Forest Resources (detailed):
- Forests cover approximately 31% of Earth's land area
- Functions: Produce oxygen (O₂), absorb carbon dioxide (CO₂), regulate climate, provide habitat for 80% of terrestrial biodiversity, prevent soil erosion, maintain water cycle, provide timber/medicine/food
- Threats: Deforestation (13 million hectares/year lost), forest fires, mining, urbanization, overgrazing, shifting cultivation
- Deforestation consequences: Climate change (less CO₂ absorption), biodiversity loss, soil erosion and floods, desertification, disrupted water cycle
- Conservation: Afforestation (planting new forests), reforestation (replanting cleared forests), sustainable harvesting, protected areas, community forestry programs, social forestry
Water Resources (detailed):
- 97% of Earth's water = saltwater (oceans). Only 3% is freshwater, and only 0.3% is easily accessible (rest is locked in glaciers/deep underground)
- Problems: Over-extraction of groundwater, water pollution (industrial/agricultural), unequal distribution, climate change affecting rainfall patterns
- Conservation methods: Rainwater harvesting (collect and store rainwater), drip irrigation (63% more efficient than flood irrigation), watershed management, waste water recycling, reducing household waste
Energy Resources:
| Conventional (Non-renewable) | Non-conventional (Renewable) |
|---|---|
| Coal, Petroleum, Natural Gas, Nuclear | Solar, Wind, Hydropower, Geothermal, Biomass, Tidal, Wave |
| High pollution, will eventually deplete | Clean, sustainable, virtually unlimited |
| Currently 80%+ of global energy | Growing rapidly, essential for future |
Mineral Resources:
- Minerals are naturally occurring inorganic substances with definite chemical composition
- Types: Metallic (iron, copper, gold) and Non-metallic (sand, limestone, salt)
- Problems: Mining causes land degradation, deforestation, water pollution, air pollution
- Conservation: Recycling metals, using substitutes, reducing waste, planned mining
📚 Biodiversity — Complete Guide
Biodiversity = the variety of life at all levels. Term coined by E.O. Wilson. India is one of the world's 17 megadiverse countries.
3 Levels of Biodiversity:
- Genetic Diversity: Variation in genes within a species. Example: different breeds of dogs (Labrador, Poodle, German Shepherd) are all the same species but genetically different. More genetic diversity = species can better adapt to changes.
- Species Diversity: Number and variety of different species in an area. A tropical rainforest has high species diversity; a desert has low.
- Ecosystem Diversity: Variety of ecosystems in a region. India has deserts, rainforests, mangroves, coral reefs, mountains — very high ecosystem diversity.
Biodiversity Hotspots: Regions with exceptionally high biodiversity that are seriously threatened. To qualify: must have ≥ 1,500 endemic plant species AND have lost ≥ 70% of original habitat. There are 36 global hotspots.
India has 4 biodiversity hotspots:
- Western Ghats — along India's western coast
- Eastern Himalayas — northeast India
- Indo-Burma — northeast India and Myanmar
- Sundaland — Nicobar Islands
Threats to Biodiversity (HIPPO mnemonic):
| Threat | Details |
|---|---|
| H — Habitat Loss | Deforestation, urbanization, agriculture destroys natural habitats. #1 cause of biodiversity loss. |
| I — Invasive Species | Non-native species that outcompete locals. Example: water hyacinth choking Indian lakes. |
| P — Pollution | Air, water, soil, noise pollution kills organisms and degrades habitats. |
| P — Population Growth | More humans = more resources consumed = more habitat destruction. |
| O — Overexploitation | Overfishing, poaching, over-hunting. Example: Indian tigers declined from 40,000+ to ~1,800. |
Conservation Strategies:
| In-situ (On-site) | Ex-situ (Off-site) |
|---|---|
| Conserve species in their NATURAL habitat | Conserve OUTSIDE natural habitat |
| National Parks: Strict protection, no human activity (e.g., Jim Corbett, Kaziranga) | Zoos: Captive breeding programs |
| Wildlife Sanctuaries: Some human activities allowed | Botanical Gardens: Plant conservation |
| Biosphere Reserves: Large areas with buffer zones (e.g., Nilgiri, Sundarbans) | Seed Banks & Gene Banks: Store genetic material for future use |
| Protects entire ecosystem | Last resort for critically endangered species |
📚 Environmental Pollution — Types, Causes, Effects, Control
Pollution = introduction of harmful substances into the environment that cause adverse changes. The substances are called pollutants.
1. Air Pollution:
| Pollutant | Source | Health/Environmental Effects |
|---|---|---|
| CO (Carbon Monoxide) | Incomplete combustion, vehicles | Binds with hemoglobin, reduces oxygen in blood → headaches, dizziness, death at high levels |
| SO₂ (Sulfur Dioxide) | Coal/oil burning, power plants | Causes acid rain, respiratory diseases, damages plants and buildings |
| NOₓ (Nitrogen Oxides) | Vehicle engines, power plants | Forms smog, acid rain, respiratory problems, ozone depletion |
| PM (Particulate Matter) | Construction, vehicles, industries, fires | PM2.5 penetrates deep into lungs → asthma, cancer, heart disease. India's biggest air quality problem! |
| CFCs (Chlorofluorocarbons) | Old ACs, refrigerators, aerosol sprays | Destroy the ozone layer → more UV radiation → skin cancer |
| CO₂ (Carbon Dioxide) | Fossil fuel burning, deforestation | Greenhouse gas → global warming and climate change |
Control measures: Use public transport, switch to renewable energy, catalytic converters in vehicles, smokestacks with filters/scrubbers, plant more trees, strict emission standards.
2. Water Pollution:
- Point sources: Single identifiable discharge point (factory pipe, sewage pipe). Easy to identify and regulate.
- Non-point sources: Diffuse, widespread (agricultural runoff, urban stormwater). Harder to control.
Major causes: Industrial effluents (chemicals, heavy metals), sewage and domestic waste, agricultural runoff (fertilizers cause algal blooms, pesticides poison water), oil spills, thermal pollution (hot water from power plants)
BOD (Biological Oxygen Demand): Amount of oxygen needed by bacteria to decompose organic matter in water. High BOD = heavily polluted (lots of organic waste consuming oxygen, killing fish).
Eutrophication: Excess nutrients (nitrogen, phosphorus from fertilizers) → algal bloom → algae die → decomposition uses all oxygen → fish and aquatic life die. This is a HUGE problem in Indian lakes.
Control: Treat sewage before discharge, reduce pesticide/fertilizer use, don't dump waste in water bodies, industrial wastewater treatment, laws and regulations.
3. Soil Pollution:
- Causes: Excessive pesticides and chemical fertilizers, industrial waste dumping, plastic waste, e-waste, mining, improper garbage disposal
- Effects: Loss of soil fertility, contaminated groundwater, food contamination, health hazards (cancer, organ damage)
- Control: Organic farming, proper waste disposal, composting, reduce plastic use, bioremediation (using organisms to clean soil)
4. Noise Pollution:
- Sound above 85 dB over prolonged exposure damages hearing
- Sources: Traffic (70-90 dB), construction (100+ dB), factories, loudspeakers, airports, firecrackers
- Effects: Hearing loss (temporary or permanent), stress, hypertension, sleep disturbance, reduced productivity, affects wildlife behavior
- Control: Sound barriers, noise regulations, green belts, silencers on machines, ear protection, noise-free zones near hospitals/schools
📚 Global Environmental Issues
1. Global Warming & Climate Change:
The greenhouse effect is a NATURAL process where certain gases in the atmosphere (like glass in a greenhouse) trap heat from the sun, keeping Earth warm enough for life (~15°C average). Without it, Earth would be ~−18°C!
The problem: Human activities have dramatically increased greenhouse gas concentrations, trapping MORE heat → enhanced greenhouse effect → global warming.
| Greenhouse Gas | Source | Contribution |
|---|---|---|
| CO₂ | Burning fossil fuels, deforestation | ~60% of warming |
| CH₄ (Methane) | Livestock, rice paddies, landfills, natural gas | ~20% |
| N₂O (Nitrous Oxide) | Fertilizers, industrial processes | ~6% |
| CFCs | Refrigeration, aerosols | ~14% |
Effects of Global Warming: Rising sea levels (threatening coastal cities like Mumbai), more extreme weather (floods, droughts, cyclones), melting glaciers (Himalayan glaciers retreating), species extinction, agricultural disruption, ocean acidification.
2. Ozone Layer Depletion:
- The ozone layer (O₃) in the stratosphere (15-35 km altitude) absorbs harmful UV-B and UV-C radiation
- CFCs rise to the stratosphere where UV light breaks them apart, releasing chlorine atoms. One chlorine atom can destroy 100,000 ozone molecules!
- Ozone hole: Severe depletion discovered over Antarctica in 1985
- UV effects on humans: Skin cancer, cataracts (eye disease), weakened immune system
- Montreal Protocol (1987): International treaty to phase out CFCs. One of the most successful environmental agreements ever — ozone layer is slowly recovering!
3. Acid Rain:
- Normal rain pH = 5.6 (slightly acidic due to dissolved CO₂). Acid rain = pH below 5.6
- Formation: SO₂ and NOₓ from factories/vehicles → combine with water vapor in atmosphere → sulfuric acid (H₂SO₄) and nitric acid (HNO₃) → fall as acidic rain
- Effects: Damages marble buildings (Taj Mahal is yellowing!), kills aquatic life, acidifies soil killing plants, corrodes metal structures, damages historical monuments
4. Solid Waste Management:
| Method | How It Works | Pros & Cons |
|---|---|---|
| Open Dumping | Waste dumped in open areas | Cheapest but worst — breeds disease, groundwater contamination, methane emission |
| Sanitary Landfill | Waste buried in lined pits, covered daily | Better than open dump. Still produces methane and leachate |
| Incineration | Burning waste at very high temperatures | Reduces volume by 90%. Produces toxic ash and air pollution if not filtered |
| Composting | Microbial decomposition of organic waste | Produces useful fertilizer. Only works for biodegradable waste |
| Recycling | Reprocessing waste materials into new products | Saves resources and energy. Not all materials recyclable |
| Vermicomposting | Using earthworms to decompose organic waste | High-quality compost. Slow process. Small scale. |
📚 Sustainable Development
Definition (Brundtland Report, 1987): "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs."
Sustainable development balances THREE pillars:
- Economic Growth — development and prosperity
- Social Equity — fair distribution of resources, poverty reduction
- Environmental Protection — preserving natural systems
Environmental Impact Assessment (EIA):
A systematic process to evaluate the environmental effects of a proposed project BEFORE it is approved. Required for major projects like dams, highways, factories, mines.
Steps: Screening (is EIA needed?) → Scoping (what impacts to study?) → Impact Analysis (detailed study) → Mitigation Measures (how to reduce negative impacts) → Public Hearing (community input) → Decision Making (approve/reject/modify)
Important Environmental Laws in India:
| Act | Year | Key Purpose |
|---|---|---|
| Wildlife Protection Act | 1972 | Protect wild animals, birds, and plants. Established national parks and sanctuaries. Made poaching illegal. |
| Water Act | 1974 | Prevent and control water pollution. Established Central and State Pollution Control Boards. |
| Forest Conservation Act | 1980 | Restrict diversion of forest land for non-forest purposes. Government approval needed to clear forests. |
| Air Act | 1981 | Prevent, control, and abate air pollution. Set emission standards for industries and vehicles. |
| Environment Protection Act | 1986 | Umbrella legislation — empowers central government to take all measures to protect and improve environment. Enacted after Bhopal Gas Tragedy (1984). |
| Biodiversity Act | 2002 | Conservation of biodiversity, sustainable use, equitable sharing of benefits. |
Key International Conferences & Agreements:
| Event | Year | Key Outcome |
|---|---|---|
| Stockholm Conference | 1972 | First major UN conference on environment. Created UNEP. June 5 = World Environment Day. |
| Rio Earth Summit | 1992 | Agenda 21 (action plan for 21st century), CBD (biodiversity convention), UNFCCC (climate framework) |
| Kyoto Protocol | 1997 | First legally binding emission reduction targets for developed nations. Developing nations (India, China) exempted. |
| Paris Agreement | 2015 | Limit global warming to well below 2°C (ideally 1.5°C) above pre-industrial levels. All countries participate. |
India's Environmental Initiatives:
- Chipko Movement (1973): Villagers hugged trees to prevent deforestation. Led by Sunderlal Bahuguna. One of India's first environmental movements.
- Project Tiger (1973): Conservation of tigers. India now has ~3,000+ tigers (from ~1,800 in 2010).
- Project Elephant (1992): Conservation of elephants and their habitats.
- National Action Plan on Climate Change (2008): 8 missions including Solar Mission, Energy Efficiency, Sustainable Habitat.
- Swachh Bharat Mission (2014): Clean India campaign — sanitation and waste management.