Environmental degradation: causes, impacts, management

Environmental Degradation – Cambridge IGCSE / A‑Level Geography (9696)

1. How the Topic Fits the Syllabus

Key Syllabus Area	What Is Covered Here
AS‑Level (Paper 1 & 2) – Physical & Human Processes	Hydrology & river hazards, atmospheric processes & climate change, earth‑processes & mass movements, population structure & migration, water resources & management, urban growth, structure & sustainability.
A‑Level extensions (Paper 3 & 4)	Tropical, coastal, arid & hazardous environments; climate‑change impacts on societies; trade, aid & tourism; disease & health geography.
Key concepts	Scale, change over time, place, spatial variation, cause‑and‑effect, systems, environmental interactions, challenges & opportunities, diversity & inclusion.
Assessment Objectives	AO1 – factual knowledge; AO2 – data/diagram interpretation, map work, quantitative analysis, sketch‑map production; AO3 – evaluation of management options.

2. Core Physical and Human Processes that Drive Degradation

2.1 Hydrology, Rivers & Flood Hazards

• Key definitions
  • Hydrograph: a graph of river discharge (or stage) against time, showing base‑flow, rising limb, peak, and recession limb.
  • Tri‑cellular model of a river basin: (1) source (headwaters), (2) transport (channel), (3) sink (floodplain, delta, offshore).
• Physical processes: precipitation → runoff → river discharge; channel erosion, sediment transport, flood‑plain aggradation.
• Degradation pathways
  • Deforestation & urbanisation increase surface runoff → higher peak flows.
  • Channel straightening & levee construction accelerate flow, reduce flood‑plain storage.
  • Sand and gravel extraction lowers riverbed, destabilises banks.
• Typical impacts: more frequent/ severe flooding, loss of fertile floodplain soils, river‑bank collapse, reduced groundwater recharge.
• Management examples
  • Integrated River‑Basin Management (IRBM) – e.g., Mekong River Commission.
  • Restoration of natural floodplains – re‑meandering, wetland creation (Yorkshire, UK).
  • Low‑impact development (LID) in urban catchments – permeable pavements, swales, rain‑garden basins.
• Temporal dimension (1900‑2020): River flood frequency in the Thames increased from an average of 1.2 events/decade (1900‑1960) to 3.4 events/decade (2000‑2020) – linked to urban expansion and climate change.

2.2 Atmospheric Processes & Climate Change

• Key drivers: combustion of fossil fuels, industrial processes, land‑use change → greenhouse‑gas (GHG) emissions.
• Global energy budget (short definition): the balance between incoming solar radiation, reflected short‑wave radiation, outgoing long‑wave radiation and the energy stored in the Earth system.
• Physical consequences
  • Global warming → sea‑level rise, altered precipitation patterns.
  • Increased frequency/intensity of extreme events (heatwaves, cyclones).
  • Atmospheric deposition of acid rain and reactive nitrogen.
• Feedback mechanisms
  • Positive feedbacks: ice‑albedo feedback, permafrost carbon release, water‑vapour feedback.
  • Negative feedbacks: increased cloud albedo, enhanced vegetation growth in some regions.
• Proxy evidence: ice‑core CO₂ records (≈ 280 ppm pre‑industrial → 420 ppm 2023), tree‑ring width series showing temperature trends, sediment cores indicating past sea‑level changes.
• Impacts on the environment: desertification in semi‑arid regions, coral bleaching, glacial retreat, loss of permafrost.
• Management & mitigation
  • International agreements – UNFCCC, Paris Agreement, Kyoto Protocol.
  • Renewable‑energy deployment – wind farms in Denmark, solar PV in Morocco.
  • Carbon capture & storage (CCS) pilots – Sleipner (Norway).
• Temporal dimension: Atmospheric CO₂ concentration rose from 315 ppm in 1958 (Mauna Loa) to 420 ppm in 2023 – a 33 % increase.

2.3 Earth‑Processes & Mass Movements

• Processes: weathering, slope failure, landslides, rockfalls, debris flows.
• Human triggers: road construction, mining, deforestation, over‑grazing.
• Impacts: loss of life & property, sedimentation of downstream reservoirs, reduced agricultural land.
• Case study: 2014‑15 Nepal landslides after an unusually intense monsoon – linked to deforestation on steep slopes.
• Management
  • Slope stabilisation – terracing, retaining walls, bio‑engineering (vetiver hedges).
  • Land‑use planning – exclusion zones, controlled quarrying.
  • Early‑warning systems using remote‑sensing and GIS.
• Temporal dimension: In the Himalaya, landslide frequency has risen by ≈ 40 % between 1990 and 2020, correlating with increased extreme rainfall events.

2.4 Population Growth, Structure & Migration

• Demographic concepts (AO1)
  • Age‑sex pyramids, dependency ratios, population momentum.
  • Demographic Transition Model (DTM): four (or five) stages – from high birth/death rates to low birth/death rates.
  • Contrast: Nigeria (Stage 2, high growth) vs. Japan (Stage 4, low growth, ageing).
• Migration drivers – push (poverty, environmental degradation, conflict) and pull (employment, education, safety) factors.
• Environmental consequences
  • Urban sprawl → loss of peri‑urban agriculture, increased waste generation.
  • Informal settlements on marginal lands – exposure to flood & landslide risk.
  • Higher demand for water, energy, and food.
• Illustrative case study: Lagos, Nigeria – >15 million inhabitants, chronic flooding due to inadequate drainage and coastal subsidence.
• Management approaches
  • Compact‑city policies – higher density, mixed‑use development.
  • Improved public transport to limit car‑related emissions.
  • Community‑based slum upgrading (e.g., Favela‑Bairro programme, Rio de Janeiro).
• Temporal dimension: World population grew from 3 billion (1960) to 8 billion (2023); annual urban‑population growth averaged 2.5 % between 2000‑2020.

2.5 Water Resources & Management

• Key issues: over‑extraction, pollution (agricultural runoff, industrial effluent), unequal allocation.
• Scale of the problem
  • Groundwater depletion in the North China Plain – ≈ 30 % drop in water‑table depth since 1990.
  • Lake Chad shrinkage – from 25 000 km² (1960) to < 2 000 km² (2020).
• Management tools
  • Integrated Water Resources Management (IWRM) – Murray‑Darling Basin Plan (Australia).
  • Water‑saving irrigation – drip systems in Israel’s Negev farms (≥ 70 % water‑use reduction).
  • Pollution control – EU Water Framework Directive, setting ecological‑status targets.
• Temporal dimension: Global freshwater withdrawal rose from 3 000 km³ yr⁻¹ (1990) to 4 200 km³ yr⁻¹ (2020), a 40 % increase.

2.6 Urban Growth, Structure & Sustainability

• Urban‑structure models
  • Concentric zone, sector, multiple‑nuclei (classical models).
  • Contemporary concepts – horizontal vs. vertical expansion, CBD change, residential zonation (inner‑city, suburban, peri‑urban).
• Environmental pressures
  • Urban heat‑island effect – temperature rise of 2–5 °C in dense cores.
  • Air‑quality degradation – PM₂.₅ exceeding WHO limits in Delhi, Beijing.
  • Storm‑water runoff – increased flood risk.
• Best‑practice examples
  • Curitiba, Brazil – integrated BRT, extensive green space, recycling (≈ 70 % household waste recycled).
  • Freiburg, Germany – solar‑city initiatives, car‑free zones, district heating.
• Management strategies
  • Green infrastructure – green roofs, permeable pavements, urban wetlands.
  • Urban growth boundaries – e.g., Portland, USA.
  • Smart‑city data platforms for real‑time energy and water monitoring.
• Temporal dimension: Between 1990 and 2020, the global urban footprint grew from 1 % to 3 % of Earth’s land surface, while the proportion of the world living in cities rose from 30 % to 56 %.

3. A‑Level Extensions – Thematic Environments

3.1 Tropical Environments

• Deforestation for oil‑palm (Indonesia) → biodiversity loss, carbon emissions, soil erosion.
• Shifting cultivation (slash‑and‑burn) in the Amazon – short‑term soil fertility, long‑term degradation.
• Management: REDD+ (Reducing Emissions from Deforestation and Forest Degradation), community‑managed forest reserves.
• Temporal box: Indonesian primary‑forest cover fell from 71 % (2000) to 53 % (2020).

3.2 Coastal Environments

• Coastal erosion accelerated by sea‑level rise and sand‑mining (Bangladesh).
• Coral‑reef bleaching – Great Barrier Reef (Australia) – temperature‑driven bleaching events (1998, 2002, 2016, 2020).
• Management: Integrated Coastal Zone Management (ICZM), mangrove restoration (Vietnam), artificial reefs.
• Temporal box: Global mean sea level rose ≈ 210 mm between 1900 and 2020 (≈ 3.3 mm yr⁻¹ in the last two decades).

3.3 Arid & Semi‑Arid Environments

• Desertification driven by over‑grazing, unsustainable irrigation (Sahel).
• Dust storms – health and agricultural impacts (Sahara dust reaching the Caribbean).
• Management: Sustainable Land Management (SLM), drip irrigation, windbreaks.
• Temporal box: The Sahel’s “green belt” (2000‑2020) shows a 15 % increase in vegetated area, yet desert‑front expansion continues northward.

3.4 Hazardous Environments

• Volcanic ash impacts on agriculture – Mt. Etna eruptions.
• Earthquake‑induced landslides – 2015 Nepal earthquake.
• Management: Hazard zoning, early‑warning systems, resilient building codes (Japan).
• Temporal box: Global fatalities from natural hazards declined from ≈ 200 000 yr⁻¹ (1970s) to ≈ 120 000 yr⁻¹ (2010‑2020) due to improved risk management.

3.5 Climate‑Change Impacts on Human Systems

• Heat‑related mortality – 2003 European heatwave (≈ 70 000 excess deaths).
• Migration pressure – “climate refugees” from low‑lying Pacific islands (Kiribati).
• Adaptation case study: Rotterdam’s “Room for the River” programme – flood‑plain reconnection, movable bridges, water squares.
• Temporal box: Global average temperature increased by 1.2 °C between 1880 and 2020.

3.6 Trade, Aid & Tourism

• Ecotourism in Costa Rica – revenue for forest protection, but risk of over‑tourism.
• Foreign direct investment in mining – environmental licences vs. community rights (Copperbelt, Zambia).
• Aid for water‑sanitation – UNICEF’s WASH programmes improving health outcomes.
• Temporal box: International tourism arrivals grew from 25 million (1990) to 1.5 billion (2019), increasing pressure on coastal and mountain environments.

3.7 Disease & Health Geography

• Vector‑borne diseases linked to environmental change – malaria resurgence in highland Ethiopia after deforestation.
• Air‑pollution health impacts – chronic respiratory disease in urban China.
• Management: Integrated disease‑surveillance, urban greening to reduce heat‑related illness.
• Temporal box: Global under‑five mortality fell from 93 deaths per 1 000 live births (1990) to 37 (2020), yet climate‑related disease burdens are rising.

4. Linking Key Concepts to the Content

Concept	How It Appears in the Notes	Temporal Illustration
Scale	Local (urban slums), regional (Mekong basin), global (climate change, Paris Agreement).	Sea‑level rise 1900‑2020 (≈ 210 mm).
Change over time	Historical land‑use change, temperature trends, groundwater‑table decline.	Global urban footprint 1990‑2020 (1 % → 3 %).
Place & Spatial Variation	Contrasting case studies – high‑income (Freiburg) vs. low‑income (Lagos) cities.	Deforestation rates 2000 vs. 2020 in Indonesia.
Cause‑and‑Effect	Deforestation → soil erosion → reduced agricultural productivity.	Over‑grazing → desertification in Sahel.
Systems & Interactions	River basin as a socio‑ecological system – water, people, industry, policy.	IRBM linking upstream land use to downstream flood risk.
Challenges & Opportunities	Renewable energy reduces emissions but needs investment and grid upgrades.	Solar PV capacity in Morocco 2020 (≈ 2 GW) vs. target 2025 (8 GW).
Diversity, Equality & Inclusion	Community‑based management emphasises local knowledge, gender‑inclusive decision‑making; flood‑risk mitigation varies between affluent and low‑income neighbourhoods.	Gender‑responsive water‑governance in Kenya (women 60 % of water‑collection labour).

5. Geographical Skills (AO2) – Practice Tasks

5.1 Interpreting a Hydrograph (River Thames 1995‑2020)

1. Identify the likely cause(s) of the increased peak after 2010.
2. Explain how urban expansion in the catchment contributes to the observed change.
3. Suggest two management interventions to reduce future peak flows.

5.2 Map Analysis – Deforestation Hotspots (Amazon 2000 vs. 2020)

• Calculate percentage change in forest cover using the legend.
• Describe the spatial pattern of loss (e.g., along roads, near river valleys).
• Discuss implications for carbon emissions and biodiversity.

5.3 Data Table – Water Use by Sector (Country X, 2010‑2020)

Year	Agriculture (km³)	Industry (km³)	Domestic (km³)
2010	45	12	8
2015	48	13	9
2020	52	15	10

1. Calculate the percentage increase in agricultural water use over the decade.
2. Discuss two possible drivers of this increase.
3. Evaluate the sustainability of current water‑use patterns, referencing UN SDG 6 (Clean Water & Sanitation).

5.4 Sketch‑Map Task – Urban Growth & Heat Island

Using a blank city map, sketch (a) the CBD, (b) residential zones (inner‑city, suburban, peri‑urban) and (c) the locations of the hottest land‑surface temperature zones. Explain why these zones are hottest and propose three mitigation measures that could be incorporated into city planning.

5.5 GIS‑Style Question – Flood‑Risk Mapping

Students are given a GIS raster showing flood‑risk probability for a river basin. Identify high‑risk catchments, explain the underlying physical and human drivers, and recommend two spatial planning policies (e.g., flood‑plain zoning, relocation of critical infrastructure).

6. Evaluation – AO3 Practice Questions

1. Assess the effectiveness of REDD+ programmes in reducing deforestation in Indonesia. Use at least two pieces of evidence (e.g., satellite data, stakeholder interviews) and consider economic, social and political factors.
2. Compare the potential of wind energy versus solar PV in meeting the UK’s 2030 net‑zero target. Discuss resource availability, intermittency, cost, and land‑use implications.
3. To what extent can Integrated Water Resources Management (IWRM) resolve conflicts over water between upstream agricultural users and downstream urban centres in the Murray‑Darling Basin? Evaluate using the concepts of equity, efficiency and environmental sustainability.
4. Evaluate the role of community‑based flood‑risk management in reducing vulnerability of informal settlements in Lagos. Consider social inclusion, financial feasibility and long‑term resilience.

7. Summary Table – Causes, Impacts & Management (Cross‑Topic)

Cause	Typical Example (Case Study)	Primary Environmental Impact	Key Management Response
Urban expansion & impervious surfaces	Lagos, Nigeria (rapid coastal city growth)	Increased flood risk, water‑quality decline, heat‑island effect	Low‑impact development, flood‑plain restoration, green‑infrastructure
Fossil‑fuel combustion	Tuoketuo coal‑fired power plant, China	Air‑pollution (PM₂.₅), GHG emissions, acid deposition	Shift to renewables, emissions‑trading scheme, CCS pilots
Intensive agriculture (synthetic fertilizers)	North China Plain	Eutrophication of rivers, groundwater nitrate contamination	Precision farming, buffer strips, integrated nutrient management
Deforestation for timber & oil palm	Sumatra, Indonesia	Soil erosion, loss of carbon sink, biodiversity loss	REDD+, community forest management, sustainable certification
Open‑pit mining	Copperbelt, Zambia	Land disturbance, heavy‑metal leaching into rivers	Re‑vegetation, strict effluent standards, progressive reclamation
Over‑grazing & unsustainable irrigation	Sahel, Africa	Desertification, loss of productive land, dust storms	SLM practices, drip irrigation, rotational grazing
Sea‑level rise & coastal erosion	Bangladesh coastal delta	Loss of land, salt‑water intrusion, displacement	Integrated Coastal Zone Management, mangrove restoration, managed retreat
Mass‑movement triggering activities	Nepal Himalaya (road cuts)	Landslides, sedimentation of reservoirs, loss of life	Slope stabilisation, land‑use planning, early‑warning systems

8. Glossary of Key Terms (AO1)

• Hydrograph – graph of river discharge (or water level) against time, showing base‑flow, rising limb, peak, and recession limb.
• Tri‑cellular model – conceptual model of a river basin divided into source, transport, and sink cells.
• Global energy budget – balance between incoming solar radiation, reflected short‑wave radiation, outgoing long‑wave radiation and energy stored in the Earth system.
• Positive feedback – process that amplifies an initial change (e.g., ice‑albedo feedback).
• Negative feedback – process that reduces or counteracts an initial change (e.g., increased cloud albedo).
• Integrated River‑Basin Management (IRBM) – coordinated management of land, water and related resources across an entire river basin.
• Integrated Water Resources Management (IWRM) – framework that promotes coordinated development and management of water, land and related resources.
• REDD+ – international mechanism to reward developing countries for reducing emissions from deforestation and forest degradation.
• Low‑impact development (LID) – set of planning and engineering practices that mimic natural hydrology to manage storm‑water runoff.
• Urban heat‑island (UHI) – phenomenon where urban areas are warmer than surrounding rural areas due to built‑up surfaces and anthropogenic heat.
• Room for the River – Rotterdam’s flood‑risk strategy that creates extra space for rivers to overflow safely.