Unit 2: Natural resources and ecosystem

I. Introduction to natural resources

Natural resources are materials and energy sources supplied by nature that humans use to sustain life and support economic activity. The unit rests on how these resources are classified, depleted, and conserved, and on the ecosystem framework that binds them together.

• Definition: any component of the natural environment (air, water, soil, minerals, organisms, sunlight) that has utility for living beings.
• Classification by origin: biotic resources (from the living world, e.g. forests, wildlife, fossil fuels) versus abiotic resources (non-living, e.g. water, minerals, land).
• Classification by availability: renewable versus non-renewable, the axis on which most conservation policy turns.
• Guiding principle: resource use should stay within nature's carrying capacity so that regeneration matches or exceeds consumption (sustainable development).

A. Renewable and non-renewable resources

The critical distinction is whether the resource replenishes on a human timescale.

1. Renewable resources: naturally regenerated within a short period.
   • Examples: solar radiation, wind, biomass, forests, water, air.
   • Caveat: renewable does not mean inexhaustible; overuse beyond regeneration rate (e.g. groundwater, fisheries) makes them behave like finite stocks.
2. Non-renewable resources: formed over geological time, effectively finite.
   • Examples: coal, petroleum, natural gas, metallic and non-metallic minerals.
   • Consequence: once consumed they are gone for practical purposes, so recycling and substitution are the only long-term responses.

II. Land resources

Land is the physical base for agriculture, forestry, settlement and industry, and its productive layer, soil, is renewable only very slowly.

A. Land resources and associated problems and remedial measures

Land degradation is the loss of the land's productive capacity through misuse.

• Soil erosion: removal of topsoil by water and wind; a fertile layer takes centuries to form but can be lost in a season.
  • Remedy: contour bunding, terracing, shelter belts, afforestation of catchments.
• Desertification: productive land turning arid through overgrazing, deforestation and drought.
  • Remedy: controlled grazing, sand-dune stabilisation, drought-resistant vegetation.
• Waterlogging and salinity: over-irrigation raises the water table and deposits salts, seen in canal-irrigated tracts.
  • Remedy: proper drainage, lined canals, gypsum application to reclaim saline-alkaline soils.
• Landslides: mass downslope movement triggered by slope-cutting for roads and mining, common in the Himalayas.
  • Remedy: retaining walls, slope drainage, restricting construction on unstable slopes.

III. Water resources

Fresh water is scarce despite covering most of the planet, and its uneven distribution drives conflict and shortage.

A. Water resources and associated problems and remedial measures

Only about 2.7% of Earth's water is fresh, and most is locked in ice caps and groundwater, so usable surface water is a tiny fraction.

• Overexploitation of groundwater: extraction faster than recharge lowers water tables and causes land subsidence.
  • Remedy: rainwater harvesting, artificial recharge, regulated pumping.
• Floods: excess runoff from deforestation and poor drainage; damages crops and settlements.
  • Remedy: embankments, reservoirs, watershed management, floodplain zoning.
• Droughts: prolonged rainfall deficit reducing soil moisture and reservoir levels.
  • Remedy: water conservation, drought-tolerant crops, inter-basin transfers where feasible.
• Conflicts over water: inter-state disputes over shared rivers (e.g. dam and river-sharing tensions).
  • Remedy: river-basin authorities, equitable allocation treaties, demand-side efficiency.
• Big dams — benefits and problems: provide irrigation and hydropower but submerge forests, displace communities and trap silt.
  • Remedy: environmental impact assessment, rehabilitation of displaced people, smaller decentralised structures.

IV. Forest resources

Forests supply timber, fuel, and countless ecological services while regulating climate and hydrology.

A. Forest resources and associated problems and remedial measures

Forests are renewable but slow-growing, so exploitation rates easily outstrip regrowth.

• Uses: timber, fuelwood, fodder, medicinal plants; ecological roles include carbon sequestration, oxygen release, watershed protection and biodiversity habitat.
• Deforestation: clearing for agriculture, logging, mining and dams.
  • Consequences: loss of biodiversity, soil erosion, disturbed water cycle, increased CO₂.
• Timber extraction and mining: open-cast mining and road building fragment forest cover.
• Effects of dams on forests and tribal people: reservoir submergence destroys forest and uproots forest-dependent tribal communities.
• Remedial measures:
  • Afforestation and reforestation: replanting degraded and cleared land.
  • Social forestry and agroforestry: community woodlots and tree-crop integration.
  • Legal protection: forest conservation legislation and protected reserves.
  • Joint Forest Management: involving local communities in protection in return for a share of produce.

V. Energy resources

Energy powers all economic activity, and the shift from finite fossil fuels to renewable sources is central to sustainability.

A. Energy resources and associated problems and remedial measures

The core problem is heavy dependence on non-renewable fossil fuels that pollute and will run out.

1. Non-renewable (conventional) energy:
   • Coal, petroleum, natural gas: high energy density but combustion releases CO₂, SO₂ and particulates, driving global warming and acid rain.
   • Nuclear: high output but risks of radioactive waste and accidents.
2. Renewable (non-conventional) energy:
   • Solar: photovoltaic cells and solar thermal; clean but intermittent and area-intensive.
   • Wind: turbines convert kinetic energy; site-specific.
   • Hydropower: flowing water drives turbines; dam-related impacts.
   • Biomass and biogas: organic matter and dung fermentation yield fuel.
   • Geothermal and tidal: heat from the Earth and tidal movement, geographically limited.
   • Remedial measures: energy conservation, efficient appliances, shift to renewables, improved public transport, and research into hydrogen and fuel cells.

VI. Role of individual in conservation of natural resources

Individual behaviour aggregated across millions determines the pressure placed on resources.

A. Role of individual in conservation of natural resources

Conservation is the planned use and protection of resources to prevent depletion and ensure availability for future generations.

• Water conservation: fixing leaks, rainwater harvesting, reusing greywater, efficient irrigation at home.
• Energy conservation: switching off unused appliances, using LED lighting, carpooling, choosing energy-efficient devices.
• Reduce, reuse, recycle: minimising consumption, reusing goods, segregating and recycling waste to cut raw-material demand.
• Sustainable choices: using public transport, avoiding single-use plastics, planting trees, composting organic waste.
• Awareness: spreading environmental literacy and supporting eco-friendly policies.

VII. Ecosystem: structure and function

An ecosystem is the functional unit that links the resources above into interacting living and non-living components.

A. Structure and function of ecosystem

An ecosystem is a community of organisms interacting with one another and with their physical environment as a self-regulating system.

• Abiotic components: physical and chemical factors — sunlight, temperature, water, soil, minerals, gases.
• Biotic components:
  • Producers (autotrophs): green plants and algae that fix solar energy through photosynthesis.
  • Consumers (heterotrophs): herbivores (primary), carnivores (secondary, tertiary).
  • Decomposers: bacteria and fungi that break down dead matter and recycle nutrients.
• Functions: energy flow through trophic levels, nutrient (biogeochemical) cycling, and ecological succession that maintains stability.

B. Types of ecosystem

Ecosystems are classified by their dominant physical environment.

1. Terrestrial ecosystems: land-based — forest, grassland, desert, characterised by soil, rainfall and temperature.
2. Aquatic ecosystems: water-based.
   • Freshwater: ponds, lakes, rivers (low salt content).
   • Marine: oceans, seas, estuaries (high salinity).

C. Energy flow in an ecosystem

Energy enters as sunlight and moves one way through trophic levels, dissipating as heat at each step.

• Source: the Sun; producers capture only about 1–2% of incident solar energy.
• Unidirectional flow: energy passes producer → herbivore → carnivore and is never recycled, unlike nutrients.
• 10% law (Lindeman): roughly only 10% of energy at one trophic level transfers to the next; the rest is lost as metabolic heat.

Sun → Producers → Primary consumers → Secondary consumers → Tertiary consumers
      (100%)        (~10%)              (~1%)                 (~0.1%)

• Implication: the energy loss limits food chains to typically four or five links.

D. Food chains and food webs

These describe who eats whom and how energy is routed through the community.

1. Food chain: a linear sequence of feeding relationships.
   • Grazing food chain: begins with living plants, e.g. grass → grasshopper → frog → snake → hawk.
   • Detritus food chain: begins with dead organic matter processed by decomposers.
2. Food web: interconnected food chains forming a network; a single species feeds at several points.
   • Significance: greater interconnection gives greater stability, since alternative food routes buffer the loss of any one species.

E. Ecological pyramids

Ecological pyramids graphically represent trophic structure, with producers at the base.

• Pyramid of numbers: counts organisms per trophic level; usually upright but inverted for a tree supporting many insects.
• Pyramid of biomass: total dry mass per level; upright on land, often inverted in oceans where small phytoplankton turn over rapidly.
• Pyramid of energy: energy content per level; always upright because of the one-way loss of energy at each transfer.

F. Ecological succession

Succession is the orderly, progressive replacement of one community by another until a stable state is reached.

• Primary succession: begins on bare, lifeless substrate (e.g. bare rock, cooled lava) colonised first by pioneer species such as lichens.
• Secondary succession: occurs where a community has been disturbed but soil remains (e.g. abandoned farmland, burnt forest); faster than primary.
• Sere and seral stages: the sequence of transitional communities leading toward the climax.
• Climax community: the final, stable, self-perpetuating community in equilibrium with the prevailing climate.