Unit 2: Natural resources and ecosystem

Natural resources are components of the environment that satisfy human needs and sustain life, while an ecosystem is the functional unit where organisms interact with their physical surroundings. This unit connects the stock of resources we exploit to the ecological systems that regenerate them.

• Natural resource: any material or energy source obtained from nature and useful to humans — soil, water, minerals, forests, sunlight.
• Ecosystem: a self-regulating community of organisms (biotic) interacting with abiotic factors (light, water, temperature, minerals) through energy flow and nutrient cycling.
• Carrying capacity: the maximum population a resource base can support indefinitely without degradation.
• Sustainability principle: use rate should not exceed regeneration rate for renewable stocks, and depletion of non-renewables should fund substitutes.

II. Introduction to Natural Resources — classification and dependence

Resources are grouped by origin and by their capacity to renew.

A. Introduction to natural resources

The foundation for the whole unit: what counts as a resource and why classification matters.

• By origin: biotic (forests, wildlife, fossil fuels from once-living matter) versus abiotic (land, water, minerals, air).
• By development stage: potential (known but unused, e.g. deep-sea minerals), actual/developed (currently exploited), reserve (part of actual usable in future).
• By distribution: ubiquitous (air, sunlight) versus localised (coal, petroleum deposits).

B. Renewable and non-renewable resources

Distinguishing resources by their rate of natural replacement.

1. Renewable: replenished by natural cycles within a human timescale.
   • Examples: solar radiation, wind, biomass, fresh water, forests.
   • Caveat: renewable only if harvest ≤ regeneration; groundwater over-pumped faster than recharge behaves as non-renewable.
2. Non-renewable: formed over geological time, fixed in stock.
   • Examples: coal, petroleum, natural gas, metallic ores.
   • Two sub-types: recyclable (metals, can be recovered) and non-recyclable (fossil fuels, lost as heat/CO₂ on combustion).

III. Land Resources — soil as the productive base

Land supplies food, minerals and living space; its thin fertile layer is easily lost.

A. Land resources

• Value: ~11% of Earth's land is arable; soil forms at roughly 1 cm per 200–1000 years, so it is effectively non-renewable.
• Uses: agriculture, forestry, mining, settlement, waste disposal.

B. Associated problems

• Soil erosion: removal of topsoil by water (sheet, rill, gully) and wind; loss of nutrients and structure.
• Desertification: productive land turns arid through overgrazing, deforestation and salinisation of irrigated soils.
• Landslides and subsidence: triggered by mining, road-cutting and slope deforestation.
• Land degradation: waterlogging, alkalinity, and contamination by pesticides and industrial waste.

C. Remedial measures

• Afforestation and shelter belts: tree lines break wind speed and bind soil.
• Contour bunding and terracing: slow runoff on slopes, cutting erosion.
• Crop rotation and cover crops: restore nitrogen and maintain cover.
• Reclamation: gypsum treatment of alkaline soils; controlled drainage for waterlogging.

IV. Water Resources — freshwater under stress

Water sustains all life yet only ~2.5% is fresh, most locked in ice.

A. Water resources

• Sources: surface water (rivers, lakes), groundwater (aquifers), and precipitation.
• Hydrological cycle: evaporation → condensation → precipitation → runoff/infiltration continuously recycles water.

B. Associated problems

• Over-exploitation of groundwater: falling water tables, dry wells, land subsidence.
• Floods and droughts: deforestation and poor drainage cause erratic extremes.
• Conflicts: inter-state and international disputes over shared rivers.
• Pollution: sewage, industrial effluent and fertiliser runoff cause eutrophication.

C. Remedial measures

• Rainwater harvesting: rooftop collection and check dams recharge aquifers.
• Watershed management: integrated treatment of a drainage basin to conserve soil and water.
• Drip and sprinkler irrigation: cut agricultural water use by 30–70% versus flood irrigation.
• Wastewater treatment and reuse: reduce load on freshwater supply.

V. Forest Resources — the biological store

Forests regulate climate, water and biodiversity while yielding timber and produce.

A. Forest resources

• Functions: productive (timber, fuelwood, resin, medicine) and protective (carbon sink, watershed protection, habitat, oxygen release).

B. Associated problems

• Deforestation: clearing for agriculture, logging, mining and dams.
• Timber extraction and mining: road-building fragments habitat and opens forests to encroachment.
• Dam construction: submerges forest and displaces communities — e.g. large river-valley projects flood wide catchments.
• Consequences: biodiversity loss, soil erosion, altered rainfall, tribal displacement.

C. Remedial measures

• Afforestation and social forestry: community planting on degraded and common land.
• Joint Forest Management (JFM): local participation in protection and benefit-sharing.
• Chipko-type movements: community resistance that embeds forests in local stewardship.
• Regulation: protected areas and logging controls.

VI. Energy Resources — powering development

Energy links every resource sector; its source determines environmental cost.

A. Energy resources

• Conventional (non-renewable): coal, petroleum, natural gas, nuclear fuel — high energy density, finite, polluting.
• Non-conventional (renewable): solar, wind, hydro, geothermal, tidal, biomass — clean but often diffuse and intermittent.

B. Associated problems

• Fossil fuel depletion: reserves finite; combustion emits CO₂, SO₂, NOₓ driving warming and acid rain.
• Nuclear risks: radioactive waste and accident hazard.
• Renewable limits: land/area demand, intermittency, high initial cost.

C. Remedial measures

• Efficiency and conservation: LED lighting, improved cookstoves, insulation reduce demand.
• Shift to renewables: solar PV, wind farms, biogas plants.
• Cogeneration: capture waste heat for combined heat and power.

VII. Role of the Individual in Conservation

Aggregate change begins with household and personal choices.

A. Role of individual in conservation of natural resources

• Water: fix leaks, reuse greywater, install low-flow fixtures.
• Energy: switch off idle appliances, use public transport, adopt efficient devices.
• Materials: practise the "3 Rs" — reduce, reuse, recycle — to cut raw-material demand.
• Land and forest: plant trees, compost organic waste, avoid single-use products.
• Awareness: informed consumption and advocacy multiply individual impact across a community.

VIII. Structure and Function of the Ecosystem

An ecosystem couples living communities to their non-living environment through matter and energy exchange.

A. Structure and function of ecosystem

• Abiotic components: inorganic (C, N, P, water), organic (proteins, lipids), and climatic factors (light, temperature).
• Biotic components — by function:
  • Producers (autotrophs): green plants, algae fixing solar energy via photosynthesis.
  • Consumers (heterotrophs): herbivores (primary), carnivores (secondary/tertiary).
  • Decomposers: bacteria and fungi that break dead matter and recycle nutrients.
• Functions: energy flow, nutrient (biogeochemical) cycling, and ecological succession.

IX. Types of Ecosystem

Ecosystems are classified by dominant physical environment.

A. Types of ecosystem

1. Terrestrial: forest, grassland, desert — vegetation set by rainfall and temperature.
2. Aquatic:
   • Freshwater: lentic (ponds, lakes, still) and lotic (rivers, streams, flowing).
   • Marine: oceans and estuaries with high salinity (~35 g/L).
   • Natural versus artificial: self-sustaining natural systems contrast with managed ones like croplands and aquaria.

X. Energy Flow in an Ecosystem

Energy moves one way through trophic levels, degrading to heat.

A. Energy flow in an ecosystem

• Source: solar radiation; producers capture only 1–2% as gross primary production.
• Trophic transfer: energy passes producer → herbivore → carnivore.
• Ten-percent law (Lindeman): roughly 10% of energy at one trophic level reaches the next; the rest is lost as respiration and heat.

Sun → Producers (1%) → Herbivores (10%) → Carnivores (10%) → Top carnivores (10%)

• Laws of thermodynamics: energy is neither created nor destroyed (first) but degrades to unusable heat at each step (second), so flow is unidirectional.

XI. Food Chains and Food Webs

Feeding relationships route energy and matter through the community.

A. Food chains and food webs

1. Food chain: a linear feeding sequence.
   • Grazing chain: grass → grasshopper → frog → snake → hawk (starts with living producers).
   • Detritus chain: dead matter → detritivores → predators (starts with dead organic matter).
2. Food web: interconnected food chains; one organism occupies several chains.
   • Significance: alternative feeding paths give stability — loss of one prey species does not collapse the whole web.

XII. Ecological Pyramids

Pyramids graph the quantity at each trophic level.

A. Ecological pyramids

• Pyramid of numbers: count of organisms per level; usually upright, inverted in a tree ecosystem (one tree supports many insects).
• Pyramid of biomass: dry mass per level; inverted in oceans where small phytoplankton support larger zooplankton mass at any instant.
• Pyramid of energy: energy per level per unit time; always upright because energy is lost at every transfer.

XIII. Ecological Succession

Communities change in a predictable sequence until they stabilise.

A. Ecological succession

• Definition: orderly, progressive replacement of one community by another at a site until a stable climax community forms.
• Types by starting substrate:
  1. Primary succession: on bare, lifeless ground (bare rock, lava, new pond); begins with pioneer species like lichens.
  2. Secondary succession: on cleared land that retains soil (abandoned farm, burnt forest); faster because soil and seeds persist.
• Stages: nudation → invasion (pioneers) → competition → reaction (organisms modify habitat) → stabilisation.
• Climax community: self-perpetuating community in equilibrium with the regional climate — e.g. an oak or deciduous forest.