Unit 5: Emerging Environmental Issues - Subjective Questions

Global warming refers to the long-term increase in Earth's average surface temperature, mainly caused by the enhanced greenhouse effect. The greenhouse effect is a natural process in which gases such as carbon dioxide, methane, nitrous oxide, and water vapour trap outgoing heat in the atmosphere.

Difference from climate change:

• Global warming specifically describes the rise in average global temperature.
• Climate change includes global warming as well as changes in rainfall, wind patterns, sea level, ocean currents, frequency of extreme weather, and the distribution of ecosystems.
• Human activities such as fossil-fuel combustion, deforestation, industrialisation, and intensive agriculture have increased greenhouse-gas concentrations.

Thus, global warming is a major component and driving force of present-day climate change.

The principal human causes of global warming are:

• Burning of fossil fuels: Coal, petroleum, and natural gas used in power generation, transport, and industries release large quantities of carbon dioxide.
• Deforestation: Cutting forests releases stored carbon and reduces the number of trees available to absorb atmospheric carbon dioxide.
• Agriculture: Livestock produce methane, while flooded rice fields and fertilised soils emit methane and nitrous oxide.
• Industrial processes: Cement production and chemical industries release greenhouse gases.
• Waste disposal: Decomposing organic waste in landfills produces methane.
• Urbanisation and consumption: Increased energy use, construction, and manufacturing raise greenhouse-gas emissions.

These activities intensify the natural greenhouse effect and cause a positive energy imbalance in the climate system.

Global warming produces several interconnected environmental effects:

• Melting of glaciers and ice sheets, contributing to sea-level rise.
• Thermal expansion of seawater, which further increases sea level.
• More frequent heat waves, droughts, intense rainfall, and certain types of storms.
• Changes in precipitation patterns, causing water shortages in some areas and floods in others.
• Ocean warming and acidification, which damage coral reefs and marine organisms.
• Shifting habitats and species ranges, forcing organisms to migrate or adapt.
• Permafrost thawing, which may release additional methane and carbon dioxide.
• Agricultural stress, caused by heat, irregular rainfall, pests, and soil-moisture loss.

The effects vary geographically, but vulnerable coastal, dryland, mountain, and polar environments are particularly at risk.

The greenhouse effect is the warming of Earth's lower atmosphere because greenhouse gases absorb and re-radiate outgoing infrared radiation.

Natural greenhouse effect:

• Naturally occurring gases, including water vapour, carbon dioxide, methane, and nitrous oxide, keep Earth warm enough for life.
• Without this effect, the average surface temperature would be approximately instead of about .

Enhanced greenhouse effect:

• Human activities increase the concentration of greenhouse gases.
• The atmosphere then absorbs more outgoing infrared radiation.
• More heat is retained, increasing global average temperature.

Therefore, the natural greenhouse effect is beneficial and necessary, whereas its human-induced intensification causes global warming and climate instability.

Sea-level rise occurs mainly because of thermal expansion of seawater and the melting of glaciers and land-based ice sheets. Its environmental consequences include:

• Coastal flooding of low-lying settlements, deltas, and islands.
• Coastal erosion and loss of beaches, wetlands, and mangrove forests.
• Saltwater intrusion into freshwater aquifers and agricultural soils.
• Destruction of coastal habitats, including nesting areas and estuaries.
• Increased storm-surge damage during cyclones and hurricanes.
• Displacement of human populations and loss of agricultural land.
• Reduced freshwater availability in coastal regions.

Adaptation measures include constructing sea walls where appropriate, restoring mangroves, protecting wetlands, improving drainage, and planning the relocation of highly exposed settlements.

Ozone depletion is the reduction in the concentration of stratospheric ozone, especially in the polar ozone layer. Ozone absorbs harmful ultraviolet-B radiation and protects living organisms.

The process involving chlorofluorocarbons (CFCs) occurs as follows:

• CFCs released from refrigeration, air-conditioning, aerosol sprays, and foam production are chemically stable in the lower atmosphere.
• They gradually reach the stratosphere.
• Ultraviolet radiation breaks CFC molecules and releases chlorine atoms.
• A chlorine atom reacts with ozone: .
• Chlorine monoxide can then react with free oxygen atoms, regenerating chlorine: .
• The regenerated chlorine continues the cycle, allowing one chlorine atom to destroy many ozone molecules.

This catalytic process produces severe seasonal ozone loss, especially over Antarctica.

Ozone depletion allows more ultraviolet-B radiation to reach Earth's surface. Its effects include:

• Human health: Increased risks of skin cancer, sunburn, premature skin ageing, and cataracts.
• Immune-system effects: Excessive ultraviolet radiation may weaken immune responses.
• Plants and crops: High ultraviolet exposure can reduce photosynthesis, growth, and crop productivity.
• Aquatic ecosystems: Ultraviolet radiation can harm phytoplankton, which form the base of many marine food chains.
• Animals: Eggs, larvae, and young organisms may be especially vulnerable.
• Materials: Plastics, rubber, paints, and fabrics may degrade more quickly.

The Montreal Protocol and its amendments have successfully reduced the production of many ozone-depleting substances. Continued monitoring and control remain essential because these chemicals can persist in the atmosphere for decades.

Stratospheric ozone depletion and ground-level ozone pollution are different environmental problems:

• Location: Stratospheric ozone occurs approximately to km above Earth, whereas ground-level ozone occurs in the lower atmosphere.
• Role: Stratospheric ozone protects life by absorbing ultraviolet radiation. Ground-level ozone is a harmful air pollutant.
• Formation or destruction: Stratospheric ozone is destroyed mainly by chlorine- and bromine-containing chemicals. Ground-level ozone forms when nitrogen oxides and volatile organic compounds react in sunlight.
• Health effects: Ground-level ozone irritates the lungs and worsens asthma, while reduced stratospheric ozone increases ultraviolet exposure.
• Environmental effects: Ground-level ozone damages crops, forests, and materials; stratospheric ozone depletion affects human health and ecosystems through increased ultraviolet radiation.

Thus, ozone is beneficial in the stratosphere but harmful when concentrated near the ground.

Deforestation is the permanent or long-term removal of forest cover so that land is converted to another use or remains degraded. Major causes include:

• Agricultural expansion: Forests are cleared for cropland, plantations, cattle ranching, and shifting cultivation.
• Commercial logging: Timber extraction supplies construction materials, paper, and furniture industries.
• Fuelwood collection: Rural households may depend on wood and charcoal for energy.
• Mining: Forests are removed for mines, roads, processing facilities, and waste storage.
• Infrastructure development: Highways, dams, railways, industries, and urban settlements fragment and clear forests.
• Population and market pressures: Demand for food, land, timber, and export commodities encourages forest conversion.
• Fires and weak governance: Uncontrolled fires, illegal logging, and poor land-use planning accelerate forest loss.

Deforestation is often driven by a combination of local livelihood needs and national or international economic demand.

Deforestation affects physical systems, ecosystems, and human communities in several ways:

• Loss of biodiversity: Forest clearance destroys habitats and may cause species extinction.
• Soil erosion: Removal of roots and canopy exposes soil to wind and water erosion.
• Decline in soil fertility: Nutrients are removed through runoff and the organic cycle is disrupted.
• Changes in the water cycle: Reduced evapotranspiration can lower local rainfall, while runoff and flood risk increase.
• Climate change: Burning and decomposition release carbon dioxide, while fewer trees remain to absorb it.
• Desertification: Repeated clearing and overuse can degrade land in dry and semi-dry regions.
• Disruption of indigenous livelihoods: Forest-dependent communities may lose food, fuel, medicine, and cultural resources.
• Habitat fragmentation: Remaining forest patches become isolated, reducing wildlife movement and breeding.

Sustainable forestry, reforestation, protected areas, and community participation can reduce these impacts.

Afforestation is the establishment of trees on land that has not recently been forested. It can increase carbon storage, reduce erosion, and create new habitats, but poorly planned plantations may reduce native biodiversity.

Reforestation is the replanting or natural regeneration of forests that have been cleared or degraded. It restores habitats, improves soil protection, and helps recover ecosystem services. Using native species and allowing natural regeneration generally produces better ecological results.

Agroforestry combines trees with crops and, in some cases, livestock on the same land. It provides food, fuel, timber, shade, soil improvement, and additional income while reducing pressure on natural forests.

Comparison:

• Afforestation creates forest cover in new areas.
• Reforestation restores previously forested areas.
• Agroforestry integrates trees with agricultural production.

All three strategies are most effective when supported by local communities, appropriate species selection, and long-term management.

Food security exists when all people, at all times, have physical and economic access to sufficient, safe, nutritious, and culturally acceptable food that meets their dietary needs for an active and healthy life.

Its four major dimensions are:

• Availability: Adequate food must be produced domestically or obtained through imports, reserves, and trade.
• Access: People must have sufficient income, land, employment, or social support to obtain food.
• Utilisation: Food must be safely prepared and nutritionally absorbed. Clean water, sanitation, healthcare, and dietary knowledge are important.
• Stability: Availability, access, and utilisation must remain secure over time and not be disrupted by conflict, disasters, price shocks, unemployment, or climate extremes.

Food security is therefore broader than food production alone; it includes nutrition, affordability, safety, and continuity.

Global warming threatens food security through several pathways:

• Heat stress: High temperatures reduce crop growth, flowering, grain formation, and livestock productivity.
• Rainfall uncertainty: Droughts reduce yields, while intense rainfall causes floods, waterlogging, and soil erosion.
• Water scarcity: Higher evaporation and changing river flows reduce irrigation water.
• Pests and diseases: Warmer conditions may expand the range and breeding period of agricultural pests.
• Soil degradation: Drought, erosion, salinisation, and desertification reduce productive capacity.
• Marine impacts: Ocean warming and acidification threaten fisheries and shell-forming organisms.
• Food-price instability: Lower production and supply disruptions can make food unaffordable for poor households.

Adaptation includes drought-resistant crops, efficient irrigation, crop diversification, climate information services, soil conservation, crop insurance, and stronger food-storage systems.

Population growth, poverty, and food insecurity are related but not identical conditions.

• Population growth increases demand for food, water, land, and energy. If production and distribution do not expand sustainably, pressure on resources may increase.
• Poverty limits people's ability to buy food, access irrigation, purchase seeds and fertilisers, obtain healthcare, or withstand price increases.
• Food insecurity results when people lack reliable access to sufficient and nutritious food.
• Poor households may cultivate marginal land, overuse soil, sell productive assets, or reduce meal quality during crises, creating a cycle of environmental degradation and poverty.
• Food insecurity can also occur in areas with adequate total food supplies if distribution is unequal, markets fail, conflict disrupts access, or people lack purchasing power.

Solutions include poverty reduction, equitable land access, rural infrastructure, education, social protection, sustainable farming, and improved food distribution.

Sustainable agriculture seeks to maintain production without degrading soil, water, biodiversity, or climate systems. Important practices include:

• Crop rotation: Maintains soil fertility and interrupts pest and disease cycles.
• Agroforestry: Trees provide shade, organic matter, wind protection, food, and additional income.
• Conservation tillage: Reduces soil disturbance, erosion, and moisture loss.
• Integrated pest management: Combines biological, cultural, mechanical, and limited chemical controls.
• Efficient irrigation: Drip irrigation and rainwater harvesting reduce water wastage.
• Organic matter management: Compost and crop residues improve soil structure and water retention.
• Crop diversification: Reduces risks from pests, market changes, and climate extremes.
• Use of locally adapted and climate-resilient varieties: Improves reliability under changing conditions.
• Improved storage: Reduces post-harvest losses and increases food availability.

These methods can strengthen the availability, access, and stability dimensions of food security.

Biodiversity is the variety and variability of living organisms and the ecological systems in which they occur.

• Genetic diversity: Variation in genes within a species or population. For example, different varieties of rice may differ in drought tolerance, disease resistance, or yield.
• Species diversity: Variety of species and their relative abundance in a community. A tropical forest generally has greater species diversity than a monoculture plantation.
• Ecosystem diversity: Variety of habitats, ecological communities, and ecological processes, such as forests, grasslands, wetlands, coral reefs, and deserts.

These levels are interdependent. Loss of habitats can reduce species diversity, while the disappearance of species and populations can reduce genetic diversity and weaken ecosystem functioning.

The major causes of biodiversity loss are often described as the main direct pressures on ecosystems:

• Habitat loss and fragmentation: Agriculture, urban growth, roads, dams, mining, and logging destroy or isolate habitats.
• Overexploitation: Unsustainable hunting, fishing, logging, and collection reduce populations faster than they can recover.
• Invasive alien species: Introduced organisms may compete with, prey on, or transmit diseases to native species.
• Pollution: Pesticides, plastics, industrial waste, oil, sewage, and excess nutrients damage organisms and habitats.
• Climate change: Altered temperature, rainfall, sea level, and ocean chemistry force species to shift ranges or adapt rapidly.
• Illegal wildlife trade: Commercial demand can severely reduce populations of plants and animals.

These pressures often reinforce one another. For example, habitat fragmentation can make species more vulnerable to climate change and invasive species.

Biodiversity is valuable because it supports ecosystem functioning, human welfare, and economic activity.

Ecological importance:

• Pollinators support the reproduction of many plants and food crops.
• Decomposers recycle nutrients and maintain soil fertility.
• Diverse ecosystems regulate water flow, climate, erosion, and pests.
• Genetic diversity increases the ability of populations to adapt to environmental change.
• Species interactions maintain food webs and ecosystem stability.

Economic and social importance:

• Biodiversity provides food, fuel, fibres, medicines, timber, and genetic resources.
• Fisheries, forestry, agriculture, and tourism depend on healthy ecosystems.
• Wetlands, forests, and mangroves provide services such as flood control and water purification.
• Natural landscapes support cultural, spiritual, educational, and recreational values.

Biodiversity loss can reduce ecosystem resilience, increase economic costs, and threaten the livelihoods of communities dependent on natural resources.

In-situ conservation protects species within their natural habitats.

• Examples include national parks, wildlife sanctuaries, biosphere reserves, marine protected areas, and community-conserved forests.
• It preserves entire ecosystems and natural interactions.
• It allows species to continue adapting to environmental conditions.
• Its effectiveness depends on habitat protection, law enforcement, local participation, and control of threats.

Ex-situ conservation protects species outside their natural habitats.

• Examples include zoos, botanical gardens, seed banks, gene banks, aquariums, and captive-breeding centres.
• It is useful for critically endangered species, preserving genetic material, research, and later reintroduction.
• It may be expensive and can reduce natural behaviour or genetic diversity if poorly managed.

In-situ conservation is generally the primary strategy, while ex-situ conservation provides valuable support when species or habitats face immediate danger.

These issues are interconnected through physical, ecological, and socioeconomic processes:

• Deforestation releases carbon dioxide and reduces carbon absorption, thereby intensifying global warming.
• Global warming increases droughts, heat waves, floods, and pest outbreaks, threatening food security.
• Agricultural expansion to meet food demand can cause further deforestation, creating a damaging feedback cycle.
• Climate change and habitat loss accelerate biodiversity loss by altering ecosystems and reducing species' ability to migrate or adapt.
• Ozone depletion increases ultraviolet radiation, which can harm crops, phytoplankton, animals, and natural ecosystems.
• Some ozone-depleting substances are also powerful greenhouse gases, showing that atmospheric issues may have multiple effects.
• Biodiversity loss weakens ecosystem services such as pollination, soil formation, water purification, and pest control, making food systems less resilient.

Integrated solutions should combine emission reduction, forest protection, sustainable agriculture, ozone-protecting policies, habitat conservation, and international cooperation.