Unit 2: Natural resources and ecosystem

I. Orientation: The Resource–Ecosystem Framework

Natural resources are the stocks of matter and energy occurring in nature that human societies use to sustain life and economic activity. The unit rests on a single governing principle: resources are drawn from ecosystems, and ecosystems are sustained by a one-way flow of solar energy coupled to a cyclic flow of matter. Modern resource science dates its policy vocabulary from the Stockholm Conference (1972) and the Brundtland Report (1987), which defined sustainable development as development "which meets the needs of the present without compromising the ability of future generations to meet their own needs."

• Introduction to natural resources: Any component of the biosphere — soil, water, minerals, forests, wildlife, solar radiation — that is usable, accessible and valuable to humans. Classified by origin (biotic/abiotic), by development stage (potential, actual, reserve, stock) and by renewability.
• Carrying capacity: The maximum population an environment can support indefinitely; exceeding it produces resource degradation rather than a temporary shortfall.
• Conservation vs. preservation: Conservation is wise, regulated use (sustained-yield forestry); preservation is protection from use (core zones of biosphere reserves).
• Thermodynamic convention: The first law fixes total energy; the second law fixes the direction — energy degrades to heat at every transfer, hence energy cannot cycle.
• Units used throughout: biomass in g/m² or t/ha; productivity in kcal/m²/yr or g C/m²/yr; energy in kilojoules; water in hectare-metres; forest area as % of geographic area.

II. Renewable and Non-Renewable Resources

The primary classification on which all management strategy depends

A. Definition and the criterion of replenishment rate

A resource is renewable if its natural regeneration rate is comparable to or faster than its rate of extraction; the distinction is therefore relative to human timescales, not absolute.

• Renewable (flow) resources: Solar radiation (~1.36 kW/m² solar constant at the top of the atmosphere), wind, biomass, fresh water, forests, soil fertility. Continuously replenished by solar and geothermal energy.
• Non-renewable (stock) resources: Coal, petroleum, natural gas, uranium, metallic ores. Formed over 10⁶–10⁸ years; the world's fossil fuels formed largely in the Carboniferous (~360–300 Ma).
• The overlap category: Renewables become effectively non-renewable when over-harvested — groundwater in Punjab and Haryana falling 0.3–1 m/yr, or soil eroding faster than the ~1 cm per 200–400 years at which it forms.
• Recyclable vs. non-recyclable non-renewables: Metals (aluminium, copper) are recoverable from scrap; fossil fuels are consumed irreversibly by combustion.

III. Land Resources

Soil as a slow-forming, thin, non-substitutable medium

A. Nature of the resource

Land supplies the physical base for agriculture, forestry, settlement and mining; only the top 15–30 cm of solum carries most of the nutrient and microbial activity.

• Composition of a fertile soil: ~45% mineral matter, ~25% air, ~25% water, ~5% organic matter (humus).
• Land-use pressure: India holds about 2.4% of the world's land area and supports about 17–18% of its population; per-capita arable land has fallen below 0.12 ha.

B. Associated problems

• Soil erosion: Sheet, rill, gully and wind erosion; the Chambal ravines and the Chos of Punjab are classic gullied landscapes. India loses an estimated 5,300 million tonnes of topsoil annually.
• Desertification: Conversion of drylands to desert through overgrazing, deforestation and salinisation — advancing margins of the Thar in Rajasthan and Gujarat.
• Waterlogging and salinity: Canal irrigation without drainage raises the water table; capillary rise deposits salts, producing usar (alkaline) and reh lands in the Indo-Gangetic plain.
• Landslides and shifting cultivation: Slope failure along Himalayan road cuttings; jhum cycles shortened from 20–30 years to 3–5 years in the North-East, preventing fallow recovery.
• Land degradation from mining and urbanisation: Overburden dumps, subsidence over coal seams (Jharia), and the loss of peri-urban farmland to construction.

C. Remedial measures

• Mechanical control: Contour bunding, terracing on slopes >5%, gully plugging with check dams, and gabion structures.
• Agronomic control: Contour ploughing, strip cropping, mulching, crop rotation with legumes, and cover crops to hold soil during monsoon rain.
• Biological control: Shelter belts and windbreaks (Prosopis, Casuarina), afforestation of catchments, and social forestry on wastelands.
• Reclamation: Gypsum application to sodic soils, sub-surface drainage for waterlogged land, and stabilisation of mine spoil by leguminous grasses.

IV. Water Resources

A renewable resource that is finite in place and time

A. Availability

Only about 2.5% of global water is fresh, and most of that is locked in ice caps and glaciers, leaving under 1% accessible in rivers, lakes and shallow aquifers.

• Indian distribution: ~4% of the world's freshwater resources; rainfall varies from ~11,000 mm/yr at Mawsynram to under 150 mm/yr in Jaisalmer, and about 75% of it falls in four monsoon months.

B. Associated problems

• Over-exploitation of groundwater: Tube-well irrigation has caused declining water tables, land subsidence, and saltwater intrusion in coastal Chennai and Gujarat.
• Floods and droughts: Simultaneous flooding in the Brahmaputra basin and drought in Marathwada in a single year illustrates a distribution problem, not merely a supply problem.
• Water pollution: Sewage and industrial effluent in the Yamuna and Ganga; fluorosis from >1.5 mg/L fluoride and arsenicosis from >0.01 mg/L arsenic in West Bengal's aquifers.
• Conflicts over water: Interstate disputes (Cauvery — Karnataka/Tamil Nadu; Satluj–Yamuna Link) and international treaties (Indus Waters Treaty, 1960).
• Dam-related problems: Submergence of forest and farmland, displacement of oustees, siltation of reservoirs and downstream flow reduction — the focus of the Narmada Bachao Andolan.

C. Remedial measures

• Rainwater harvesting: Rooftop collection, recharge pits, and revived traditional systems — tankas in Rajasthan, johads in Alwar, ahar-pyne in Bihar.
• Watershed management: Ridge-to-valley treatment integrating contour trenches, vegetative cover and percolation tanks (Ralegan Siddhi, Hiware Bazar).
• Efficiency and reuse: Drip and sprinkler irrigation (40–60% water saving over flood irrigation), treated-effluent reuse, and volumetric pricing.

V. Forest Resources

Ecosystem services and the timber–subsistence conflict

A. Functions and status

Forests supply timber, fuelwood, fodder, non-timber products (gum, resin, lac, honey) and, more critically, regulate hydrology, carbon and soil.

• Policy benchmark: The National Forest Policy (1988) targets 33% of geographic area under forest; recorded forest cover is around 21–24%.

B. Associated problems

• Deforestation: Drivers are shifting cultivation, timber extraction, fuelwood demand, fires and encroachment.
• Developmental projects: Big dams (Silent Valley controversy), mining, and highway alignment fragment contiguous canopy.
• Consequences: Loss of biodiversity and habitat, soil erosion, disturbed hydrological cycle, reduced carbon sequestration, and human–wildlife conflict.

C. Remedial measures

• Legal and institutional: Forest (Conservation) Act 1980, Joint Forest Management (from 1990) sharing usufruct with village committees, and compensatory afforestation.
• People's movements: Chipko (Reni village, 1974) and Appiko (Karnataka, 1983) as models of community resistance to felling.
• Technical: Agroforestry, silvipasture, fuel-efficient chulhas and LPG substitution to cut fuelwood demand.

VI. Energy Resources

Substitution away from a finite carbon stock

A. Classification

Energy resources divide by renewability and by conversion route.

• Conventional: Coal (~55% of India's commercial energy), petroleum, natural gas, thermal, hydro and nuclear power.
• Non-conventional: Solar (photovoltaic and thermal), wind, biomass and biogas, geothermal, tidal, ocean thermal (OTEC), and hydrogen fuel cells.

B. Associated problems

• Depletion and import dependence: India imports over 80% of its crude oil; reserves-to-production ratios make petroleum the tightest constraint.
• Emissions: CO₂ driving global warming, SO₂ and NOₓ causing acid rain, fly ash from thermal plants, and radioactive waste from fission requiring 10³–10⁵ year isolation.
• Renewables' own limits: Diffuse and intermittent supply, high capital cost, land requirement, and low capacity factors for wind (~20–30%).

C. Remedial measures

• Efficiency: Cogeneration, LED lighting, BEE star labelling, and reduction of transmission and distribution losses.
• Deployment: Grid-connected solar parks, wind farms in Tamil Nadu and Gujarat, biogas plants delivering ~0.2–0.3 m³ gas per kg cattle dung.

VII. Role of Individual in Conservation of Natural Resources

Individual behaviour aggregates into national demand; conservation therefore begins at the point of consumption.

• Water: Fix leaking taps (a dripping tap wastes ~1,000+ L/yr), bucket bathing over showers, rooftop harvesting, and reuse of RO reject water.
• Energy: Switch off standby loads, set air-conditioners at 24–26 °C, use public transport or car-pooling, and prefer 5-star appliances.
• Materials: The 5 Rs — Refuse, Reduce, Reuse, Repurpose, Recycle; segregate wet and dry waste; compost kitchen waste.
• Land and forest: Plant and maintain trees, avoid single-use plastic and paper waste, prefer certified timber, and support local produce to cut transport energy.
• Civic: Vote, participate in environmental impact hearings, and use the Right to Information Act to monitor local projects.

VIII. Ecosystem: Structure and Function of Ecosystem

The functional unit of nature (term coined by A.G. Tansley, 1935)

A. Structure of ecosystem

Structure is the composition and physical organisation of the system.

• Abiotic components: Climatic factors (light, temperature, rainfall, humidity) and edaphic factors (soil, pH, minerals, water); inorganic substances (C, N, P, H₂O) and organic substances (proteins, lipids, humus).
• Biotic components:
  • Producers (autotrophs): Green plants, algae, chemosynthetic bacteria; fix solar energy through photosynthesis.
  • Consumers (heterotrophs): Herbivores (primary), carnivores (secondary, tertiary), omnivores.
  • Decomposers (saprotrophs): Bacteria and fungi mineralising detritus and returning nutrients.
• Species and stratification: Vertical layering (canopy–understorey–shrub–herb–litter) and horizontal zonation.

B. Function of ecosystem

Function is the set of processes that keep the structure operating.

• Energy flow: Unidirectional, from sun → producers → consumers → decomposers, degrading to heat.
• Nutrient cycling: Biogeochemical cycles — gaseous (carbon, nitrogen) and sedimentary (phosphorus, sulphur).
• Productivity:

GPP = total energy fixed by producers per unit area per unit time
NPP = GPP − R          (R = respiration loss by producers)
Secondary productivity = energy stored by consumers
Units: kcal m⁻² yr⁻¹  or  g dry matter m⁻² yr⁻¹

• Homeostasis: Self-regulation through negative feedback (predator–prey oscillation).

IX. Types of Ecosystem

Ecosystems are classified first as natural or artificial, then by medium.

• Terrestrial: Forest (tropical rain, deciduous, temperate, taiga), grassland (savanna, prairie, steppe), and desert (hot and cold; xerophytes with reduced leaves, CAM photosynthesis).
• Aquatic — freshwater:
  1. Lentic (still): Ponds and lakes, zoned into littoral, limnetic and profundal.
  2. Lotic (running): Streams and rivers, with higher dissolved oxygen and current-adapted biota.
• Aquatic — marine: Oceans (avg. salinity 35 ppt), estuaries (variable salinity, high productivity), coral reefs and mangroves.
• Artificial: Croplands, aquaculture ponds, urban ecosystems — dependent on human energy subsidy.

X. Energy Flow in an Ecosystem: Food Chains and Food Webs

A. Principle of energy flow

Energy enters as sunlight, of which only 1–5% of incident PAR is fixed, and is progressively lost as respiratory heat.

• Lindeman's 10% law (1942): Roughly 10% of energy at one trophic level transfers to the next; hence chains rarely exceed 4–5 links.
• Trophic levels: T₁ producers, T₂ herbivores, T₃ primary carnivores, T₄ top carnivores.

B. Food chains

• Grazing food chain (GFC): Begins with living green plants — grass → grasshopper → frog → snake → hawk.
• Detritus food chain (DFC): Begins with dead organic matter — leaf litter → earthworm/fungi → bird; dominant in forests, where the bulk of NPP is not grazed.

C. Food webs

• Definition: Interconnected food chains sharing species, giving alternative pathways.
• Stability function: If rabbits decline, a fox may switch to rodents; more links means greater resilience to species loss.

XI. Ecological Pyramids

Graphical representation of trophic structure (Charles Elton, 1927)

• Pyramid of numbers: Counts of organisms per level. Upright in grassland; inverted in a tree ecosystem (one tree supports thousands of insects).
• Pyramid of biomass: Standing crop in g/m². Upright in forests; inverted in oceans, where a small phytoplankton biomass with rapid turnover supports a larger zooplankton biomass.
• Pyramid of energy: Energy in kcal/m²/yr. Always upright, because the second law forbids a level from passing on more energy than it receives.

XII. Ecological Succession

Orderly, directional change in community composition at a site over time

A. Process and stages

• Sequence: Nudation → invasion (migration, ecesis, aggregation) → competition and coaction → reaction (biota modify the habitat) → stabilisation (climax).
• Seral stages: The transient communities; the whole sequence is a sere.

B. Types

1. Primary succession: On a bare, never-previously-colonised substrate (lava flow, bare rock, new sand dune). Pioneers are crustose lichens; extremely slow — often 1,000+ years to forest.
2. Secondary succession: On a site cleared but retaining soil (abandoned field, burnt forest). Faster, since seed bank and nutrients survive; pioneers are annual weeds.

• By moisture regime: Hydrarch (hydrosere, starting in water, moving toward mesic) and xerarch (xerosere, starting on dry rock, also moving toward mesic).

C. Trends toward climax

• Increasing: Species diversity, biomass, niche specialisation, nutrient retention, and food-web complexity.
• Decreasing: Net community productivity (GPP approaches respiration, so P/R → 1), and rate of change.
• Climax concepts: Monoclimax (climate alone determines the endpoint), polyclimax (soil, fire and grazing yield several stable endpoints).