Unit 5: Emerging Environmental Issues

I. Orientation

Emerging environmental issues are large-scale changes in Earth’s atmosphere, ecosystems, and resource systems caused by interacting natural processes and human activities. Since the Industrial Revolution, especially after the mid-twentieth century, fossil-fuel use, industrial agriculture, urbanisation, mining, and land-use change have intensified environmental pressures. These issues are interconnected: climate change can accelerate biodiversity loss, deforestation can reduce food security, and ozone depletion can increase harmful ultraviolet radiation.

• Human–environment relationship: Human societies depend on air, water, soil, forests, biodiversity, and stable climatic conditions.
• Environmental change: A change may be natural, but its present speed, scale, and distribution are strongly influenced by human activity.
• Global commons: The atmosphere, oceans, and climate system cross national boundaries, requiring international cooperation.
• Sustainability: Development should meet present needs without undermining the ecological conditions required by future generations.
• Systems approach: Environmental problems should be analysed through causes, processes, impacts, feedbacks, and management responses.
• Unequal vulnerability: Poorer communities often contribute less to environmental degradation but face greater exposure and fewer adaptation resources.

II. Global warming — Rising average temperatures and climate disruption

Global warming is the long-term increase in Earth’s average surface temperature, mainly caused by the enhanced greenhouse effect. Greenhouse gases absorb outgoing infrared radiation and re-radiate part of it toward Earth’s surface. Carbon dioxide concentration increased from about 280 parts per million before industrialisation to over 400 parts per million in the twenty-first century.

A. Global warming and its environmental effects

Global warming alters physical systems, ecosystems, and human environments through rising temperatures and associated climatic changes.

• Greenhouse mechanism: Incoming short-wave solar radiation warms Earth’s surface; outgoing long-wave radiation is absorbed by gases such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapour.
• Main sources: Coal, oil, and gas combustion release CO₂; livestock and rice cultivation produce methane; fertilisers release nitrous oxide; deforestation reduces carbon storage.
• Temperature rise: Higher global mean temperatures increase the frequency of heatwaves, warm nights, and temperature extremes.
• Cryosphere change: Mountain glaciers retreat, snow cover declines, and polar ice sheets lose mass. Melting land ice contributes to sea-level rise, unlike melting floating sea ice, which has little direct effect on sea level.
• Sea-level rise: Thermal expansion of warming seawater combines with melting glaciers and ice sheets, threatening deltas, islands, coastal wetlands, and low-lying cities.
• Hydrological effects: Warmer air can hold more moisture, intensifying heavy rainfall in some regions, while altered circulation and evaporation increase drought risk in others.
• Ocean impacts: Absorption of CO₂ forms carbonic acid, lowering ocean pH and making it harder for corals and shell-forming organisms to build calcium-carbonate structures.
• Ecosystem shifts: Species may move poleward or to higher elevations. Those unable to migrate or adapt face population decline and local extinction.
• Positive feedbacks: Melting snow reduces surface reflectivity, while thawing permafrost can release CO₂ and methane, reinforcing warming.
• Responses: Mitigation reduces causes through renewable energy, energy efficiency, public transport, and forest protection; adaptation includes flood barriers, drought-resistant crops, early-warning systems, and heat-action plans.

B. Significance and limitations

The effects of global warming vary by place and depend on exposure, sensitivity, and adaptive capacity.

• Geographical inequality: Small island states face coastal inundation, while semi-arid regions may experience worsening water stress and crop failure.
• Agricultural pressure: Heat, drought, floods, pests, and changing growing seasons can reduce yields, although some high-latitude areas may temporarily gain longer growing seasons.
• Health risks: Heat stress, malnutrition, respiratory illness, and vector-borne diseases such as malaria may increase under suitable conditions.
• Management limitation: Adaptation cannot fully protect ecosystems or settlements from irreversible losses, especially where warming causes ice-sheet instability or species extinction.
• Climate justice: Effective policy combines emissions reduction with finance, technology transfer, and support for communities facing unavoidable impacts.

III. Ozone depletion — Reduction of stratospheric ozone

Ozone depletion is the thinning of the stratospheric ozone layer, especially over Antarctica during the spring season. Ozone is concentrated approximately 15–35 kilometres above Earth and absorbs much of the Sun’s harmful ultraviolet-B (UV-B) radiation. The 1987 Montreal Protocol controls ozone-depleting substances and is widely regarded as a major environmental success.

A. Ozone depletion

Ozone depletion occurs when human-made chlorine- and bromine-containing compounds release reactive atoms that destroy ozone molecules in the stratosphere.

• Ozone formation: Ultraviolet radiation splits oxygen molecules (O₂); free oxygen atoms then combine with O₂ to form ozone (O₃).
• Major chemicals: Chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform were used in refrigeration, aerosols, fire suppression, and industrial cleaning.
• Catalytic destruction: In sunlight, a CFC releases chlorine. One chlorine atom can repeatedly destroy many ozone molecules through reactions involving chlorine monoxide.
• Polar ozone hole: Very low temperatures create polar stratospheric clouds. Their surfaces convert inactive chlorine compounds into reactive forms; sunlight in Antarctic spring then triggers rapid ozone destruction.
• Environmental effects: Increased UV-B damages phytoplankton, disrupts aquatic food webs, harms crops, and affects materials such as plastics and paints.
• Human health: Excess UV-B raises risks of skin cancers, cataracts, and immune-system impairment.
• Global distinction: Ozone depletion concerns stratospheric ozone loss, whereas ground-level ozone is an air pollutant formed by reactions between nitrogen oxides and volatile organic compounds.
• International response: The Montreal Protocol phased out many ozone-depleting substances, and the ozone layer is expected to recover gradually as atmospheric concentrations decline.

B. Significance and limitations

Ozone protection demonstrates that coordinated international environmental governance can reduce a global atmospheric threat.

• Policy success: Restrictions on CFC production caused atmospheric concentrations of several ozone-depleting substances to decline.
• Long atmospheric lifetime: Some CFCs persist for decades, so recovery is slow even after production controls.
• Climate connection: Many ozone-depleting substances are also powerful greenhouse gases; their control has therefore provided climate benefits.
• Continuing risks: Illegal emissions, poorly managed refrigerants, and replacement chemicals with high global-warming potential can create new environmental problems.
• Scientific monitoring: Satellite observations, ground stations, and seasonal measurements are necessary to track recovery and detect unexpected changes.

IV. Deforestation — Conversion and degradation of forests

Deforestation is the permanent or long-term removal of forest cover and conversion of forested land to another use. Forest degradation is a related process in which ecological quality declines without complete clearing. Tropical forests are especially important because they store carbon, regulate water cycles, and contain high biodiversity.

A. Deforestation

Deforestation results from direct land conversion and from pressures that reduce forest regeneration and ecological function.

• Agricultural expansion: Cattle ranching, soybean cultivation, oil-palm plantations, shifting cultivation, and commercial crops are major causes in tropical regions.
• Logging: Selective logging removes valuable trees and opens roads, increasing access, fragmentation, fire risk, and further clearing.
• Infrastructure and extraction: Roads, dams, mines, settlements, and energy projects replace or divide forest habitats.
• Fuelwood collection: In some areas, heavy dependence on wood fuel contributes to woodland degradation, particularly where population pressure and poverty are high.
• Carbon cycle: Burning and decomposition release stored carbon as CO₂; fewer trees also reduce future carbon absorption.
• Soil impacts: Removal of canopy and roots increases erosion, nutrient loss, compaction, and runoff. In tropical climates, intense rainfall can rapidly remove exposed topsoil.
• Water regulation: Forests intercept rainfall, support infiltration, and return water through evapotranspiration. Clearing can increase floods during storms and reduce dry-season flows.
• Social consequences: Forest-dependent communities may lose land, livelihoods, food sources, cultural sites, and medicinal plants.
• Control measures: Protected areas, community forestry, agroforestry, sustainable certification, reforestation, and supply-chain monitoring can reduce forest loss.

B. Significance and limitations

Deforestation is both a local land-use problem and a global environmental concern.

• Fragmentation: A continuous forest divided into isolated patches develops more edge habitat, which alters temperature, humidity, predation, and species survival.
• Fire feedback: Drier and fragmented forests burn more easily; fires release carbon and may convert forest into persistent grassland.
• Development dilemma: Restricting forest conversion without providing alternative incomes can impose costs on rural communities.
• Reforestation limits: Planting trees cannot immediately replace the complex soils, species interactions, and carbon stocks of an old-growth forest.
• Effective governance: Secure land rights, enforcement against illegal clearing, local participation, and economic incentives are more effective than rules that lack implementation capacity.

V. Food security — Reliable access to adequate and nutritious food

Food security exists when all people, at all times, have physical and economic access to sufficient, safe, nutritious food that meets dietary needs and preferences for an active and healthy life. It has four connected dimensions: availability, access, utilisation, and stability.

A. Food security

Food security depends on production, distribution, purchasing power, nutrition, and resilience to environmental and economic shocks.

• Availability: Food must be produced domestically or obtained through trade. Crop yields depend on soil fertility, water, climate, seeds, labour, and technology.
• Access: Food may be available in markets but unaffordable to poor households because of low income, unemployment, conflict, or high prices.
• Utilisation: Safe water, sanitation, healthcare, and dietary diversity determine whether nutrients are absorbed and used effectively.
• Stability: Households require dependable access despite droughts, floods, pests, war, economic crises, or supply-chain disruption.
• Environmental pressures: Soil erosion, salinisation, water scarcity, biodiversity loss, and climate change threaten long-term agricultural productivity.
• Production systems: Monocultures can produce high yields but increase vulnerability to pests, disease, and input-price shocks.
• Sustainable responses: Crop diversification, conservation agriculture, integrated pest management, rainwater harvesting, agroforestry, and improved storage can strengthen resilience.
• Food waste: Losses during harvesting, transport, storage, retail, and consumption reduce effective food availability and waste land, water, and energy.

B. Significance and limitations

Food security is not simply a question of producing more food; it also concerns equity, nutrition, and ecological sustainability.

• Climate sensitivity: A heatwave during flowering can sharply reduce cereal yields, while drought can lower both crop production and livestock feed availability.
• Population and consumption: Rising population and resource-intensive diets increase pressure on land and water, although unequal consumption is also important.
• Technological trade-offs: Irrigation, fertilisers, and improved seeds can raise yields but may cause groundwater depletion, eutrophication, soil degradation, or chemical pollution.
• Policy priorities: Stable land rights, farmer support, climate information, local seed systems, and social protection improve access and resilience.
• Long-term principle: Productive agriculture must maintain soil, water, pollinators, and genetic diversity rather than maximise short-term output alone.

VI. Loss of biodiversity — Decline in the variety of life

Biodiversity includes variation within species, between species, and among ecosystems. Loss of biodiversity occurs when populations decline, species become extinct, genetic diversity narrows, or habitats and ecological processes are degraded.

A. Loss of biodiversity

Biodiversity loss is driven by multiple interacting pressures, often summarised as habitat change, overexploitation, pollution, invasive species, and climate change.

• Habitat destruction: Agriculture, urban growth, roads, dams, and mining replace or fragment habitats; habitat loss is the leading broad cause of species decline.
• Overexploitation: Overfishing, hunting, logging, and wildlife trade remove organisms faster than populations can recover.
• Pollution: Pesticides, plastics, oil, heavy metals, sewage, and excess fertiliser harm organisms; nutrient enrichment can produce algal blooms and oxygen-poor dead zones.
• Invasive species: Introduced organisms may outcompete, prey on, or transmit diseases to native species lacking effective defences.
• Climate change: Warming, altered rainfall, ocean acidification, and extreme events shift habitats and disrupt seasonal relationships such as flowering and pollination.
• Genetic erosion: Small or isolated populations lose genetic variation, reducing their ability to adapt to disease, climate stress, and environmental change.
• Ecosystem services: Biodiversity supports pollination, soil formation, water purification, carbon storage, coastal protection, medicines, and cultural values.
• Conservation measures: Protected areas, habitat corridors, restoration, sustainable harvesting, invasive-species control, seed banks, and community conservation address different levels of biodiversity.
• Analytical dimension: Conservation must balance intrinsic value, ecosystem function, human livelihoods, and the rights of local and Indigenous communities.