Unit 2: Natural resources and ecosystem

CHE110 — Environmental Studies 12 min read

I. Orientation — Earth systems and ecological interdependence

Natural resources are materials, organisms, and environmental conditions obtained from nature and used by living organisms, especially humans. An ecosystem is a functional unit in which biotic communities interact with one another and with abiotic surroundings. Resource use and ecosystem stability are linked: excessive extraction can reduce biodiversity, disrupt energy flow, and weaken ecosystem services.

Resource basis: Air, water, soil, minerals, sunlight, plants, animals, and fossil fuels support life and human development.
Sustainability principle: Resources should be used within their regeneration capacity, while wastes should remain within the environment’s assimilative capacity.
Ecosystem principle: Matter cycles through ecosystems, but energy flows in one direction—from the Sun to producers and then to consumers and decomposers.
Interdependence: Changes in one component, such as removal of forests, can affect soil, water, climate, food chains, and human livelihoods.
Conservation aim: Protection combines efficient use, restoration, pollution control, biodiversity protection, and responsible individual behavior.

II. Natural resources — Classification and use

Natural resources are naturally occurring substances or processes that provide ecological, economic, or cultural benefits. Their value depends on availability, accessibility, quality, and the rate at which people use them.

A. Introduction to natural resources

This subsection establishes the meaning and importance of resources in environmental studies.

Definition: A resource is useful when it supplies a recognized need; for example, groundwater provides drinking water and iron ore provides raw material for steel.
Resource categories: Biotic resources include forests, wildlife, and fisheries; abiotic resources include land, water, air, sunlight, and minerals.
Ecosystem services: Forests store carbon, wetlands reduce floods, and insects pollinate crops—services often provided without direct market payment.
Pressure factors: Population growth, urbanization, industrialization, and consumption increase extraction and waste generation.

B. Renewable and non-renewable resources

This subsection distinguishes resources by their capacity and timescale of replacement.

Renewable resources: Solar radiation, wind, flowing water, forests, and wildlife can renew naturally, but overuse may make them effectively scarce.
- Condition: A renewable resource remains sustainable only when extraction is at or below its regeneration rate; harvesting fish faster than reproduction causes depletion.
Non-renewable resources: Coal, petroleum, natural gas, and metallic minerals form over geological periods and are depleted by use.
- Examples: Coal originates from buried plant matter, while petroleum forms from transformed organic sediments over millions of years.
Management contrast: Renewable resources require regulated use and regeneration; non-renewable resources require efficiency, recycling, substitution, and development of alternatives.

III. Land resources — Use, degradation, and restoration

Land is the terrestrial surface used for agriculture, settlements, forests, transport, industry, and wildlife habitats. Its productivity depends on soil depth, nutrients, structure, water availability, and biological activity.

A. Land resources and associated problems and remedial measures

This subsection explains how land-use change causes degradation and how damaged land can be restored.

Agricultural pressure: Intensive cultivation, excessive irrigation, and repeated monocropping can cause nutrient loss, salinity, waterlogging, and reduced soil organic matter.
Soil erosion: Removal of vegetation allows wind and water to carry away fertile topsoil; sheet, rill, and gully erosion are common forms.
Deforestation and urbanization: Clearing vegetation exposes soil, while construction converts productive land into impermeable surfaces.
Desertification: In dry regions, overgrazing, deforestation, and poor irrigation may transform productive land into degraded, desert-like terrain.
Remedial measures: Contour ploughing slows runoff on slopes; terrace farming creates level steps; strip cropping and shelterbelts reduce wind erosion.
Soil improvement: Crop rotation, compost, green manure, mulching, and controlled fertilizer use restore nutrients and organic matter.
Water management: Drip irrigation reduces evaporation; drainage and salt-tolerant crops help control waterlogging and salinity.
Planning approach: Land-use zoning, reclamation of mined areas, afforestation, and prevention of uncontrolled construction protect land capability.

IV. Water resources — Availability, pollution, and conservation

Water resources include surface water, groundwater, glaciers, atmospheric moisture, and oceans. Although water is continuously cycled, usable freshwater is limited and unevenly distributed.

A. Water resources and associated problems and remedial measures

This subsection examines water scarcity, contamination, and practical conservation.

Major sources: Rivers, lakes, reservoirs, wetlands, aquifers, and rainwater supply freshwater; groundwater is stored in pores and fractures below the water table.
Scarcity: Over-extraction lowers groundwater levels, dries wells, causes land subsidence, and may permit saltwater intrusion in coastal aquifers.
Pollution: Sewage adds pathogens and organic matter; fertilizers add nitrates and phosphates; industries may release heavy metals, acids, dyes, or toxic chemicals.
Eutrophication: Excess nitrogen and phosphorus stimulate algal growth; decomposition then consumes dissolved oxygen, producing fish kills and “dead zones.”
Floods and droughts: Deforestation and paved surfaces increase rapid runoff and flooding, while rainfall variability and overuse intensify drought.
Remedial measures: Treat domestic sewage and industrial effluents before discharge; treatment may include screening, biological oxidation, and disinfection.
Conservation methods: Rainwater harvesting, watershed management, recharge pits, restoration of wetlands, water metering, and reuse of treated wastewater improve supply.
Efficient use: Drip irrigation and repair of leaking pipelines reduce loss; the principle is to match water quality to use rather than use drinking-quality water everywhere.

V. Forest resources — Ecological and human importance

Forests are complex communities dominated by trees and associated plants, animals, fungi, and microorganisms. They provide products, habitats, climate regulation, and protection of soil and water.

A. Forest resources and associated problems and remedial measures

This subsection connects forest benefits with threats and conservation practices.

Products: Timber, fuelwood, bamboo, fibers, fruits, medicines, gums, and resins support rural and industrial economies.
Ecological services: Canopies intercept rainfall, roots bind soil, and forests store carbon; transpiration also contributes to local moisture and climate regulation.
Deforestation: Agriculture, mining, roads, dams, urban expansion, and fuelwood collection remove forest cover and fragment habitats.
Consequences: Deforestation increases erosion, floods, carbon dioxide emissions, biodiversity loss, and human–wildlife conflict.
Degradation pressures: Overgrazing, invasive species, forest fires, pests, and unsustainable logging reduce regeneration and habitat quality.
Remedial measures: Afforestation establishes trees on previously non-forested land; reforestation restores forests after clearing or disturbance.
Sustainable management: Selective harvesting, reduced-impact logging, social forestry, agroforestry, protected areas, and community participation combine production with conservation.
Protection principle: Natural forests should not be treated as equivalent to plantations, because plantations usually contain fewer species and simpler habitats.

VI. Energy resources — Demand, impacts, and alternatives

Energy resources provide power for transport, industry, agriculture, domestic use, and communication. Energy choices influence air pollution, climate change, land use, and resource security.

A. Energy resources and associated problems and remedial measures

This subsection compares conventional and alternative energy sources and their environmental effects.

Conventional sources: Coal, petroleum, natural gas, and large hydropower have supported industrial development but cause significant ecological impacts.
Environmental problems: Burning fossil fuels releases carbon dioxide, sulfur oxides, nitrogen oxides, particulate matter, and sometimes mercury; these contribute to warming, smog, acid deposition, and disease.
Extraction impacts: Mining damages land and may pollute water; oil drilling, transport, and spills threaten marine and coastal ecosystems.
Renewable alternatives: Solar photovoltaic cells convert sunlight to electricity; wind turbines use moving air; biogas forms by anaerobic decomposition; geothermal energy uses Earth’s heat.
Other sources: Nuclear energy produces low operational carbon emissions but creates radioactive-waste, safety, and high-capital concerns.
Remedial measures: Improve energy efficiency, use public transport, adopt cleaner fuels, install pollution-control equipment, and expand decentralized renewable systems.
Energy conservation: LED lighting, efficient appliances, building insulation, fuel-efficient vehicles, and combined heat-and-power systems reduce energy demand.

VII. Role of individual in conservation of natural resources

Individual choices influence resource demand, waste generation, and public environmental behavior. Conservation becomes effective when personal action is supported by community institutions and sound policy.

A. Role of individual in conservation of natural resources

This subsection identifies practical responsibilities in daily life.

Reduce consumption: Buy durable products, avoid unnecessary packaging, and prevent food waste; reducing demand lowers extraction and energy use.
Reuse and recycle: Carry reusable bags and bottles, repair goods, and separate paper, metal, glass, organic waste, and hazardous waste at source.
Conserve water: Close taps while brushing, repair leaks, harvest rainwater, and reuse greywater for gardening where safe.
Conserve energy: Switch off unused equipment, use efficient appliances, prefer walking, cycling, public transport, or shared vehicles.
Protect biodiversity: Avoid wildlife products, plant native species, prevent littering, and keep domestic animals from harming wildlife.
Participate: Join watershed, tree-planting, cleanliness, and local biodiversity programs; report illegal dumping, hunting, or tree felling.

VIII. Structure and function of ecosystem — Components and interactions

An ecosystem contains abiotic factors and biotic organisms linked by energy transfer, nutrient cycling, and population interactions. Its function emerges from relationships among these components.

A. Structure and function of ecosystem

This subsection describes the organization and processes that maintain an ecosystem.

Abiotic structure: Light, temperature, rainfall, soil, pH, minerals, oxygen, and salinity determine which organisms can survive.
Biotic structure: Producers make organic matter; consumers obtain it by feeding; decomposers break down dead material.
Functional processes: Photosynthesis stores solar energy, feeding transfers energy, and decomposition returns mineral nutrients to soil and water.
Interactions: Predation, competition, parasitism, mutualism, and commensalism regulate populations and community structure.
Productivity: Gross primary productivity is total photosynthetic production; net primary productivity equals gross production minus plant respiration.

B. Types of ecosystem

This subsection classifies ecosystems by origin, habitat, and dominant environmental conditions.

Natural ecosystems: Forests, grasslands, deserts, ponds, lakes, rivers, oceans, and estuaries develop through natural processes.
Artificial ecosystems: Croplands, gardens, reservoirs, and aquariums are managed by humans and often require external inputs.
Terrestrial ecosystems: Land ecosystems are shaped strongly by rainfall, temperature, soil, and vegetation—for example, deserts have low rainfall and sparse producers.
Aquatic ecosystems: Freshwater systems have low salinity, while marine systems have high salinity; estuaries combine river water and seawater.
Scale: A pond may be a small ecosystem, whereas the biosphere is the global ecosystem containing all life-supporting regions.

IX. Energy flow in an ecosystem — One-way transfer

Energy enters most ecosystems as sunlight, is captured by producers, and passes through trophic levels with substantial loss as heat. Unlike nutrients, energy is not recycled.

A. Energy flow in an ecosystem

This subsection explains the direction and efficiency of energy transfer.

Primary capture: Chlorophyll-based photosynthesis converts light energy into chemical energy stored in glucose and plant biomass.
Trophic transfer: Energy moves from producers to herbivores, carnivores, and decomposers through feeding relationships.
Heat loss: Respiration releases energy for metabolism, but much becomes heat; therefore, energy available declines at higher trophic levels.
Ten-percent principle: Only a small fraction—often approximated as 10%—passes to the next trophic level; the value is an ecological approximation, not a fixed law.
Energy model: Food chains generally begin with producers and end with decomposers, which use dead organic matter from all levels.

X. Food chains and food webs — Feeding relationships

Food chains show a single pathway of food transfer, whereas food webs show interconnected pathways within a community.

A. Food chains and food webs

This subsection explains grazing and detritus-based feeding pathways.

Grazing chain: Green plants → grasshopper → frog → snake → eagle begins with living producers and proceeds through herbivores and carnivores.
Detritus chain: Dead leaves → earthworm → bird → hawk begins with dead organic matter and is especially important in forests and soils.
Food web: A grassland mouse may eat seeds and be preyed upon by snakes, owls, and foxes; multiple links increase realism and often stability.
Trophic level: Producers occupy the first trophic level; primary consumers the second; secondary and tertiary consumers follow.
Disturbance effect: Removing a predator or producer can cause cascading changes across several connected populations.

XI. Ecological pyramids — Quantitative representation

Ecological pyramids represent relationships among trophic levels in terms of number, biomass, or energy. The broad base normally consists of producers.

A. Ecological pyramids

This subsection distinguishes the three pyramid forms and their limitations.

Pyramid of numbers: Shows the number of organisms at each level; it may be inverted when one tree supports many insects.
Pyramid of biomass: Shows standing biological mass, commonly measured as grams per square metre; aquatic systems may be inverted because phytoplankton reproduce rapidly.
Pyramid of energy: Shows energy flow, often in kJ m⁻² year⁻¹, and is always upright because energy is lost between levels.
Interpretive limit: Pyramids simplify complex food webs and may not represent decomposers or organisms occupying multiple trophic positions.

XII. Ecological succession — Gradual community change

Ecological succession is the orderly, directional change in species composition and community structure over time. It results from environmental modification by organisms, disturbance, competition, and changing resource availability.

A. Ecological succession

This subsection compares primary and secondary succession and identifies the typical sequence.

Primary succession: Begins on a lifeless surface without soil, such as newly exposed rock after a lava flow; lichens and microbes help initiate soil formation.
Secondary succession: Begins where soil remains after disturbance, such as fire, cultivation, or storms; it is usually faster than primary succession.
Typical sequence: Pioneer species colonize first, followed by grasses and herbs, shrubs, and eventually a relatively stable mature community.
Mechanisms: Facilitation improves conditions for later species; competition eliminates less-suited species; tolerance allows some species to persist under changing conditions.
Climax concept: A mature community may remain relatively stable under prevailing climate, but modern ecology recognizes continuing disturbance and change rather than permanent equilibrium.
Human influence: Restoration ecology can accelerate succession through soil improvement, native planting, invasive-species removal, and protection from repeated disturbance.