Unit 2: Natural resources and ecosystem

CHE110 — Environmental Studies 12 min read

I. Orientation

Natural resources are materials, organisms, and environmental processes that support life and human societies. An ecosystem is a functional unit in which biotic organisms interact with one another and with abiotic surroundings. Conservation follows the principle of sustainable development: use resources to meet present needs without reducing the ability of future generations to meet theirs.

Resource base: Air, water, soil, minerals, forests, wildlife, sunlight, and fossil fuels provide ecological and economic benefits.
Interdependence: Energy enters ecosystems mainly as sunlight, while matter such as carbon, nitrogen, and water cycles continuously.
Carrying capacity: Every environment has limits determined by available food, water, space, and waste-absorbing ability.
Sustainability: Resource use must remain within regeneration rates for renewable resources and minimize depletion of non-renewable resources.
Conservation approach: Prevention, efficient use, restoration, recycling, and community participation are more effective than uncontrolled exploitation.

II. Natural resources — types and significance

Natural resources are useful components of nature obtained directly or indirectly for survival, production, and ecological stability. Their value may be material, cultural, biological, or life-supporting.

A. Introduction to natural resources

This introduction establishes why natural resources are essential but limited.

Definition: A natural resource is a naturally occurring substance or process used by organisms; examples include groundwater, timber, iron ore, and solar radiation.
Classification by origin: Biotic resources come from living organisms, such as forests and fisheries; abiotic resources include land, minerals, air, and water.
Classification by use: Resources may supply food, raw materials, energy, habitat, medicines, or ecosystem services such as pollination and flood control.
Resource pressure: Population growth, urbanization, industrialization, and consumption increase extraction, pollution, and habitat conversion.
Ecosystem services: Wetlands filter water, forests store carbon, and insects pollinate crops, even when these services are not directly sold.

B. Renewable and non-renewable resources

This distinction depends on the rate at which a resource is naturally replaced compared with its rate of use.

Renewable resources: Sunlight, wind, flowing water, forests, soil fertility, and wildlife can regenerate, but only if harvesting remains within natural renewal rates.
Non-renewable resources: Coal, petroleum, natural gas, metallic ores, and many minerals form over geological timescales and are effectively finite for human use.
Important condition: A renewable resource can become exhaustible; overfishing may remove fish faster than reproduction, and groundwater pumping may exceed recharge.
Conservation principle: Use renewable resources sustainably, substitute renewable energy for fossil fuels, and recycle non-renewable materials such as aluminium and copper.
Environmental cost: Extraction can cause mining scars, oil spills, methane emissions, soil loss, and air pollution even before final consumption.

III. Land resources — use, degradation, and restoration

Land is the terrestrial platform for settlements, agriculture, forests, transport, and wildlife. Its productivity depends on soil structure, nutrients, water, vegetation, and responsible management.

A. Land resources and associated problems and remedial measures

This topic links land use to degradation and practical restoration.

Major uses: Cropland produces food, grazing land supports livestock, forests provide habitat and products, and urban land supports housing and infrastructure.
Soil erosion: Water and wind remove fertile topsoil; contour ploughing, terracing, cover crops, shelterbelts, and check dams reduce runoff.
Deforestation and overgrazing: Removal of vegetation exposes soil and lowers infiltration; afforestation, rotational grazing, and controlled cutting restore cover.
Salinity and waterlogging: Excess irrigation raises groundwater and deposits salts; drip irrigation, drainage, salt-tolerant crops, and efficient scheduling help.
Desertification: Drylands lose biological productivity through drought, vegetation removal, and poor land use; watershed management and drought-resistant vegetation are remedies.
Urban and industrial pressure: Construction seals soil and waste contaminates land; zoning, brownfield redevelopment, soil testing, and safe waste treatment limit damage.
Conservation agriculture: Minimum tillage, compost, crop rotation, and integrated pest management maintain organic matter and reduce chemical dependence.

IV. Water resources — availability, contamination, and management

Water resources include surface water, groundwater, glaciers, rainfall, and marine water. Although abundant globally, usable freshwater is unevenly distributed and vulnerable to pollution.

A. Water resources and associated problems and remedial measures

This topic explains water scarcity, pollution, and conservation together.

Sources and uses: Rivers, lakes, reservoirs, aquifers, and rainwater support drinking, irrigation, sanitation, industry, hydropower, and ecosystems.
Scarcity: Population growth, drought, unequal distribution, and over-extraction lower water availability; rainwater harvesting and recharge structures improve local supplies.
Groundwater depletion: Excess pumping lowers the water table and may cause land subsidence or seawater intrusion; regulated withdrawal and artificial recharge are necessary.
Pollution: Sewage adds pathogens and nutrients, industries add toxic metals, and farm runoff adds fertilizers and pesticides.
Eutrophication: Excess nitrogen and phosphorus stimulate algal growth; decomposition consumes dissolved oxygen and can kill fish.
Remedial treatment: Screening, sedimentation, biological treatment, disinfection, and industrial effluent control reduce contamination before discharge.
Efficient use: Drip irrigation delivers water near roots, low-flow fixtures reduce domestic demand, and wastewater can be treated for reuse.
Watershed management: Vegetation, contour barriers, wetlands, and check dams slow runoff, reduce erosion, and improve groundwater recharge.

V. Forest resources — ecological value and conservation

Forests are complex renewable resources that provide products, habitat, climate regulation, soil protection, and cultural benefits. Their regeneration is slower than many human demands.

A. Forest resources and associated problems and remedial measures

This topic examines forest benefits, threats, and conservation strategies.

Resource products: Timber, fuelwood, bamboo, fibres, fruits, resins, gums, and medicinal plants support livelihoods and industries.
Ecological functions: Forest canopies intercept rainfall, roots bind soil, and vegetation stores carbon and moderates local temperature.
Deforestation: Agriculture, roads, mining, dams, logging, and urban expansion remove or fragment habitat.
Biodiversity loss: Fragmentation isolates populations and increases edge effects; wildlife corridors, protected areas, and habitat restoration maintain connectivity.
Forest degradation: Selective cutting, fires, invasive species, and overharvesting reduce structure and regeneration without complete clearing.
Remedial measures: Afforestation creates tree cover, reforestation restores cleared land, and sustainable forestry limits harvest to planned regeneration.
Community participation: Joint forest management, indigenous stewardship, non-timber livelihoods, and controlled grazing connect conservation with local welfare.
Protection method: Preventing fires, enforcing anti-poaching laws, and monitoring satellite-detected forest loss improve management.

VI. Energy resources — supply, impacts, and transition

Energy resources power transport, agriculture, homes, communication, and industry. Energy choices influence climate change, pollution, health, and resource security.

A. Energy resources and associated problems and remedial measures

This topic compares conventional and alternative energy and identifies ways to reduce harm.

Conventional sources: Coal, petroleum, natural gas, and large hydropower provide concentrated energy but may cause mining damage, spills, displacement, and pollution.
Renewable sources: Solar, wind, small hydropower, biomass, geothermal, and tidal energy are replenished naturally, though availability can be intermittent.
Pollution effects: Burning fossil fuels releases carbon dioxide, sulfur oxides, nitrogen oxides, particulate matter, and sometimes mercury.
Climate impact: Carbon dioxide strengthens the greenhouse effect; energy efficiency and renewable generation reduce emissions per unit of useful energy.
Nuclear energy: Fission produces high energy with low operational carbon emissions but creates radioactive waste and requires strict safety systems.
Remedial measures: Efficient appliances, public transport, building insulation, cleaner fuels, emission controls, and decentralized solar reduce demand and pollution.
Energy transition: Battery storage, smart grids, diversified generation, and demand management address the intermittency of wind and solar power.

VII. Individual conservation — everyday responsibility

Conservation is not limited to governments or industries; individual choices aggregate into substantial reductions in extraction, waste, and pollution.

A. Role of individual in conservation of natural resources

This topic translates ecological principles into household and community action.

Reduce consumption: Purchase durable goods, avoid unnecessary packaging, and repair items to lower raw-material extraction.
Water protection: Close taps, repair leaks, harvest rainwater, reuse greywater where safe, and never pour oils or chemicals into drains.
Energy saving: Switch off unused equipment, use efficient lighting, choose public transport, walk, cycle, and support renewable electricity.
Waste hierarchy: Refuse unnecessary products, reduce use, reuse materials, segregate waste, compost organics, and recycle suitable items.
Land and forest care: Plant native species, prevent litter and fires, use paper carefully, and avoid products linked to illegal logging.
Civic role: Join local clean-ups, report pollution, support conservation laws, and participate in watershed or biodiversity programs.
Consumption awareness: Food choices, water use, travel, and electricity have ecological footprints extending beyond the household.

VIII. Ecosystem — organization and operation

An ecosystem is a self-regulating functional system formed by organisms and their physical environment. Its operation depends on interactions, energy transfer, and nutrient cycling.

A. Structure and function of ecosystem

This topic identifies ecosystem components and the processes connecting them.

Abiotic structure: Light, temperature, rainfall, soil, minerals, pH, oxygen, and salinity determine which organisms can survive.
Biotic structure: Producers make organic matter; consumers obtain food from organisms; decomposers break down dead material.
Trophic organization: Organisms occupy trophic levels according to how they obtain energy and matter.
Functions: Ecosystems capture energy, transfer nutrients, decompose wastes, regulate populations, and maintain productivity.
Productivity: Gross primary productivity is total producer photosynthesis; net primary productivity equals gross productivity minus plant respiration.
Nutrient cycling: Decomposers return mineral nutrients to soil and water, allowing producers to reuse elements such as carbon and nitrogen.
Interactions: Predation, competition, parasitism, mutualism, and decomposition influence population size and community structure.

B. Types of ecosystem

This classification emphasizes dominant habitat conditions and characteristic organisms.

Terrestrial ecosystems: Forests, grasslands, deserts, and tundra differ in rainfall, temperature, soil, and vegetation.
Aquatic ecosystems: Ponds, lakes, rivers, wetlands, estuaries, and oceans vary in salinity, depth, flow, and oxygen.
Natural ecosystems: A forest or lake develops mainly through natural processes, although human influence may still occur.
Artificial ecosystems: Croplands, aquariums, reservoirs, and urban parks require substantial human management and external inputs.
Boundary systems: Estuaries and wetlands connect land and water and often support high productivity and biodiversity.

IX. Energy transfer and feeding relationships

Energy flow describes movement of usable energy through trophic levels, while feeding relationships show who obtains energy from whom.

A. Energy flow in an ecosystem

This topic explains why energy decreases at successive trophic levels.

Primary input: Green plants and algae convert solar energy into chemical energy through photosynthesis.
One-way movement: Energy passes from producers to consumers and decomposers, then dissipates as heat; unlike nutrients, it is not recycled.
Ten-percent principle: Only a small fraction, commonly approximated as 10%, transfers to the next trophic level; the exact value varies.
Productivity limit: If producers store 10,000 kilojoules, primary consumers may receive roughly 1,000 kilojoules and secondary consumers about 100 kilojoules.
Energy loss: Respiration, movement, heat production, undigested material, and excretion reduce transfer efficiency.
Implication: Food chains are usually short because little energy remains to support organisms at high trophic levels.

B. Food chains and food webs

This topic represents feeding pathways and the ecological consequences of their connections.

Food chain: A linear sequence begins with a producer, such as grass, followed by herbivores and successive carnivores.
Grazing chain: Energy moves from living plants to herbivores, for example grass → grasshopper → frog → snake.
Detritus chain: Dead leaves and organic waste are consumed by decomposers and detritivores, such as earthworms and fungi.
Food web: Interconnected chains provide alternative food pathways and make ecosystems more stable than a single chain.
Trophic transfer: Removal of a predator can increase herbivores and reduce vegetation, producing a trophic cascade.
Human influence: Pesticides, overfishing, and habitat loss alter feeding links and may cause biomagnification of persistent toxins.

X. Ecological patterns through time

Ecological patterns show how populations are arranged and how communities change after disturbance or environmental development.

A. Ecological pyramids

This topic compares trophic levels using numbers, biomass, or energy.

Pyramid of numbers: It displays individuals at each level; one tree supporting many insects can produce an inverted shape.
Pyramid of biomass: It shows total living mass, usually in grams per square metre; aquatic systems may have lower phytoplankton biomass than zooplankton at a given moment.
Pyramid of energy: It shows energy flow per area per time, such as kilojoules per square metre per year, and is always upright because energy is lost between levels.
Interpretive limit: Pyramids simplify complex food webs and may not represent omnivory or organisms occupying several trophic levels.
Best comparison: Energy pyramids most clearly express the second law of thermodynamics and declining transfer efficiency.

B. Ecological succession

This topic describes the orderly change in species composition and ecosystem structure over time.

Primary succession: It begins on lifeless surfaces without soil, such as new volcanic rock; lichens and microbes help form initial soil.
Secondary succession: It begins where soil remains after fire, cultivation, or storms; grasses, shrubs, and trees may recolonize more rapidly.
Pioneer community: Early colonizers tolerate severe conditions, stabilize substrates, and add organic matter.
Seral stages: Each stage modifies light, moisture, nutrients, and shelter, allowing different species to replace earlier communities.
Climax concept: A relatively stable mature community may develop under prevailing climate, although disturbances continually reset or redirect succession.
Human influence: Grazing, invasive species, pollution, and repeated clearing can arrest succession; protection and assisted natural regeneration can restore ecosystems.
Significance: Succession explains ecosystem recovery, soil development, biodiversity change, and planning for habitat restoration.