2024 Cambridge IGCSE Environmental Management (0680) Practice Paper with Answers

Any two of:
- Habitat protection / prevents habitat destruction / limits logging and development.
- Legal protection for species / prevents hunting / poaching.
- Promotes natural biodiversity and maintains gene pools.
- Offers opportunities for controlled scientific research or education.

Award 1 mark for each valid benefit up to a maximum of 2 marks.
- Accept: prevents deforestation / habitat loss
- Accept: protects gene pool / prevents extinction
- Reject: general 'helps the environment' statements

Any two of:
- Visual pollution / scarring of the landscape.
- Loss of vegetation / destruction of habitats.
- Siltation of nearby water bodies / rivers due to surface runoff of loose sediment.
- Landslides / instability of waste heaps.

Award 1 mark for each valid environmental problem up to a maximum of 2 marks.
- Accept: dust pollution from dry heaps
- Accept: soil degradation / loss of topsoil

1. Increased water demand for domestic, industrial, and commercial use exceeds the local natural freshwater supply or infrastructure capacity.
2. Poor sanitation infrastructure leads to sewage pollution of water bodies, reducing the availability of clean, safe water.

Award 1 mark for explaining increased demand exceeding supply.
Award 1 mark for explaining pollution of existing water sources making them unusable.

Any two of:
- Intermittency / unreliable resource (wind doesn't always blow).
- Visual pollution (unattractive on the landscape).
- Noise pollution from the blades.
- Hazard to birds / bats.
- Large land area required (though land underneath can still be used).

Award 1 mark for each valid disadvantage up to a maximum of 2 marks.
- Accept: high initial capital cost
- Reject: 'causes pollution' (must specify visual or noise)

Any two of:
- Conversion of carbon monoxide (\(CO\)) into carbon dioxide (\(CO_2\)).
- Conversion of nitrogen oxides (\(NO_x\)) into nitrogen gas (\(N_2\)) and oxygen gas (\(O_2\)).
- Oxidation of unburnt hydrocarbons into carbon dioxide (\(CO_2\)) and water (\(H_2O\)).

Award 1 mark for each described conversion up to a maximum of 2 marks.
- Must state the reactant and the converted product to gain the mark.

State: Ploughing across the slope / along the contour lines (rather than up and down).
Explain: The ridges and furrows act as mini-dams, reducing the speed of surface runoff and encouraging water infiltration, which prevents water from washing the soil away.

Award 1 mark for stating that ploughing is done across the slope / horizontally / along contours.
Award 1 mark for explaining that this slows down surface runoff / traps soil and water.

Any two of:
- Volcanic soils are fertile / rich in nutrients, allowing high crop yields.
- Tourism provides jobs and boosts the local economy.
- Availability of geothermal energy for cheap electricity / heating.
- Extraction of valuable minerals (e.g., sulfur) found near volcanic sites.
- Poverty / lack of choice / ancestral connection to the land.

Award 1 mark for each valid reason up to a maximum of 2 marks.
- Accept: fertile soil / agriculture
- Accept: geothermal energy / tourism / mineral mining

Any two of:
- Provision of clean, chlorinated / bottled drinking water.
- Boiling water before drinking / use of water purification tablets.
- Safe sewage disposal / proper sanitation facilities (preventing human waste from contacting water sources).
- Promoting personal hygiene practices, such as handwashing with soap.
- Vaccination programs against water-borne pathogens.

Award 1 mark for each valid preventative method up to a maximum of 2 marks.
- Accept: water chlorination / purification / boiling
- Accept: proper sewage treatment / disposal

A buffer zone is an area of land surrounding a highly protected core zone. By restricting intense human development in this outer area, it absorbs edge effects and human disturbances. It permits low-impact activities like ecotourism or sustainable harvesting, which provides local communities with income and reduces the incentive to illegally exploit resources inside the national park's core, thereby protecting the resident species.

Award 1 mark for each valid point up to a maximum of 2 marks:
• acts as a physical barrier / transition area that absorbs human disturbance / edge effects;
• allows sustainable human activities (e.g., ecotourism, agroforestry) which reduces illegal poaching/logging inside the core area;
• reduces human-wildlife conflict by preventing direct contact at the park boundary.

While high-income countries often have better building regulations and emergency services that lower casualty rates, the monetary value of their built environment is significantly higher. An earthquake in a highly developed urban area damages extremely expensive assets, infrastructure, and high-tech industries, and causes major economic disruption to businesses, leading to massive financial losses.

Award 1 mark for each valid point up to a maximum of 2 marks:
• infrastructure, buildings, and technology are of much higher monetary value / more expensive to repair or replace;
• higher indirect costs from business interruption, insurance claims, and disruption to global supply chains.

Subsurface mining is localized underground, which means the massive surface excavation associated with open-cast mining is avoided. This preserves the overlying forest or grassland ecosystems, protects topsoil from being completely stripped away, and minimizes noise and air pollution on the surface.

Award 1 mark for each correct advantage up to a maximum of 2 marks:
• less surface land disturbance / less habitat destruction / less deforestation;
• less soil erosion / preservation of surface topsoil;
• less surface air pollution (dust) / less noise pollution on the surface;
• smaller visual impact / less visual pollution.
Reject: 'cheaper' or any economic advantages.

Steep, rugged mountain slopes present major physical barriers. It is challenging and expensive to construct transport networks, utilities, and settlements. Furthermore, mountains often have harsh climates and poor, thin soils that limit agricultural productivity, resulting in fewer people living there.

Award 1 mark for identifying the overall effect and 1 mark for the explanation:
• Effect (1 mark): Results in low population density / sparsely populated areas;
• Explanation (1 mark): Steep slopes make transport / building infrastructure difficult OR poor soils / cold climate make farming difficult.

Geothermal energy relies on heat from the Earth's crust, which is only accessible at shallow, cost-effective depths in specific geologically active areas, such as near plate boundaries. Additionally, the high upfront financial risk and cost of drilling deep exploratory wells prevent many countries from developing this resource.

Award 1 mark for each valid reason up to a maximum of 2 marks:
• geographically restricted / only accessible near active tectonic plate boundaries / volcanic areas / hot spots;
• high capital / setup / drilling / exploration costs;
• risk of releasing toxic underground gases (e.g., hydrogen sulfide) / causing localized seismic instability during drilling.

Tropical cyclones require heat and moisture from warm ocean waters, typically at least \(26.5^\circ\text{C}\) extending to a depth of about 50 meters, to fuel the system. They also require the Coriolis effect to cause the system to spin, which prevents them from forming right on the Equator (they need to be at least \(5^\circ\) latitude away).

Award 1 mark for each correct physical condition up to a maximum of 2 marks:
• warm sea surface temperature / ocean water of at least \(26.5^\circ\text{C}\);
• deep layer of warm water (at least 50 m);
• high humidity / moist air in the lower-to-mid troposphere;
• sufficient Coriolis force / distance from the Equator (at least \(5^\circ\) latitude north or south);
• low vertical wind shear.

A fertile soil must have spaces filled with air (gaseous phase). Plant roots are living tissues that require oxygen from these pore spaces to carry out aerobic respiration, which generates the energy needed for active transport of nutrients. Additionally, beneficial soil bacteria and fungi require oxygen to break down organic material into inorganic nutrients that plants can use.

Award 1 mark for each valid point up to a maximum of 2 marks:
• provides oxygen for root respiration (which is needed for active transport / nutrient uptake);
• provides oxygen for aerobic soil microbes / decomposers / nitrogen-fixing bacteria;
• prevents anaerobic conditions which can lead to root rot / toxic compound buildup.

To use pitfall traps effectively: 1. Set up a grid or transect in both the managed pine plantation and the old-growth forest to ensure random or systematic sampling. 2. Dig holes and place plastic cups so their rims are flush with the soil surface, allowing beetles to fall in. 3. Leave the traps for a set duration (such as 24 hours) to standardize the sampling time. 4. Collect, identify, and count the target beetle species, then calculate the mean catch per trap to compare relative abundance.

[1] for placing multiple traps in both areas using a systematic grid or transect. [1] for ensuring trap rims are level/flush with the soil surface. [1] for standardizing the trap duration (e.g., leaving them for 24 hours). [1] for counting the beetles in each trap and calculating the mean/average relative abundance for comparison.

Open-cast mining negatively impacts the environment in several ways. For water: 1. Rainfall washes loose sediment and silt from exposed mine faces into rivers, causing siltation and reducing water quality. 2. Leaching of toxic chemicals or heavy metals from mine tailings into the groundwater contaminates drinking and irrigation water. For soil: 3. Heavy vehicles compact the soil, reducing pore spaces and preventing crop root growth. 4. Wind disperses toxic mine dust onto nearby agricultural fields, which lowers soil pH or reduces crop photosynthesis.

Max [2] for water pollution: [1] for surface runoff causing siltation/turbidity in rivers; [1] for toxic chemicals/metals leaching into groundwater or streams. Max [2] for soil degradation: [1] for soil compaction by heavy machinery reducing water infiltration/root growth; [1] for windblown dust/chemical deposition reducing soil fertility or crop yield.

Decommissioning a coal-fired power station for an offshore wind farm offers significant environmental benefits: 1. Wind energy is renewable and produces no greenhouse gases (such as carbon dioxide) during operation, reducing the community's carbon footprint. 2. It eliminates air pollutants like sulfur dioxide, which cause acid rain. However, the economic challenges include: 3. The initial capital investment for marine construction and underwater cabling is extremely high. 4. The intermittent nature of wind requires expensive energy storage systems or backup power grids to ensure constant electricity supply.

Max [2] for environmental benefits: [1] for reduction of greenhouse gases / carbon dioxide emissions; [1] for elimination of sulfur dioxide / nitrogen oxides (preventing acid rain). Max [2] for economic challenges: [1] for high capital installation / construction costs offshore; [1] for high marine maintenance costs / intermittency requiring expensive backup or storage solutions.

Physical factors heavily influence population density: 1. Relief/Terrain: Coastal plains are flat, which facilitates the construction of roads, railways, and settlements. 2. Soil fertility/Water supply: Alluvial soils near coasts are highly fertile, allowing for intensive crop cultivation to sustain large populations, while mountains often have steep, rocky slopes and thin, acidic soils that are unsuitable for farming.

[1] for identifying flat relief/terrain, and [1] for explaining that it facilitates infrastructure construction / urban development. [1] for identifying fertile soil / reliable water supply, and [1] for explaining that it supports agriculture / food production for large populations.

To reduce the vulnerability of a city to a volcanic eruption, authorities can: 1. Use real-time monitoring (e.g., seismographs to detect tremors, tiltmeters for ground swelling, and gas spectrometers) to predict eruptions. 2. Designate hazard zones using land-use planning to prevent development in areas likely to be affected by pyroclastic flows. 3. Construct engineering defenses like physical barriers or channels to divert lahars (mudflows) or lava. 4. Educate the population and conduct emergency response drills, ensuring stockpiles of safety equipment (like dust masks) are available.

[1] for real-time monitoring (seismometers, tiltmeters, gas emission tracking) to provide early warnings. [1] for land-use zoning / hazard mapping to restrict development in high-risk zones. [1] for engineering structures (barriers, diversion channels) to control lahars or lava flows. [1] for public education / emergency preparedness drills to improve community resilience.

Transmission: 1. Flooding inundates sanitation infrastructure, causing sewage and fecal matter containing the cholera pathogen to contaminate drinking water sources. 2. High population density in temporary shelters with poor hygiene increases person-to-person spread via contaminated food or water. Management: 3. Provision of clean, treated drinking water (using chlorine tablets, boiling water, or distributing bottled water). 4. Setting up rapid rehydration clinics (Oral Rehydration Therapy) to treat infected individuals and prevent deaths.

Max [2] for transmission: [1] for floodwater damaging sewage infrastructure and mixing human waste with drinking water; [1] for ingestion of water containing Vibrio cholerae. Max [2] for management: [1] for supplying clean drinking water / water purification tablets / boiling instructions; [1] for setting up medical clinics with oral rehydration therapy (ORT) / establishing hygienic temporary latrines.

Crop rotation and biological pest control are key to sustainable agriculture: 1. Crop rotation prevents soil depletion by alternating nutrient-demanding crops with nitrogen-fixing crops (legumes), maintaining soil fertility naturally. 2. Alternating crops breaks the reproductive cycles of pests and diseases that host on specific plant species. 3. Biological control introduces natural predators (such as ladybirds to eat aphids), which avoids chemical pesticide use. 4. This combination prevents pesticide runoff into local water bodies, protects non-target biodiversity, and avoids bioaccumulation in the food chain.

Max [2] for crop rotation: [1] for alternating crops to maintain soil fertility / plant nitrogen-fixing legumes; [1] for breaking the life cycle of species-specific pests/pathogens. Max [2] for biological control: [1] for using natural predators to control pest populations, reducing chemical pesticide reliance; [1] for preventing chemical runoff / protecting non-target insects / avoiding pest resistance.

Acid rain formation: 1. Sulfur dioxide (SO2) is emitted from combustion and rises into the atmosphere. 2. It reacts with water molecules (H2O) and oxygen to form dilute sulfuric acid (H2SO4), lowering the pH of precipitation. Source reduction technology: 3. Wet scrubbers (flue-gas desulfurization) are installed in exhaust stacks. 4. The flue gas is sprayed with a slurry of limestone (calcium carbonate), which reacts with the SO2 to form solid calcium sulfate (gypsum), effectively removing it from the waste gas.

Max [2] for acid rain formation: [1] for sulfur dioxide reacting with water vapor/oxygen in the atmosphere; [1] for the formation of sulfuric acid lowering the pH of rainfall. Max [2] for technology: [1] for identifying flue-gas desulfurization / wet scrubbers; [1] for explaining that an alkaline slurry (limestone/lime) reacts with and neutralizes the sulfur dioxide in the exhaust stack.

Open-cast mining completely removes the surface vegetation and topsoil, directly destroying the habitats of diverse species. Without tree roots, the exposed soil is highly vulnerable to erosion during heavy tropical rainstorms, leading to siltation of local rivers. Runoff containing harmful heavy metals or chemicals used in processing pollutes local water sources, disrupting food chains. Additionally, the constant dust from blasting coats vegetation, inhibiting photosynthesis, and the noise forces sensitive animal species to abandon the area.

Award 1 mark for each distinct, valid negative ecological impact described, up to a maximum of 4 marks:
- Habitat loss / deforestation leading to loss of biodiversity / disruption of food webs.
- Soil erosion / loss of fertile topsoil / siltation of rivers due to runoff.
- Water pollution / leaching of toxic heavy metals or acidic mine drainage into aquatic ecosystems.
- Noise pollution / blasting disrupting animal behavior / migration / breeding patterns.
- Air pollution / dust coating leaves and reducing rate of photosynthesis.
(Do not accept socio-economic impacts such as loss of agricultural jobs or relocation of towns, as the question specifies the local ecosystem).

Fish quotas set legal limits on the quantity of fish that can be caught. This keeps harvesting levels below the maximum sustainable yield, allowing populations to remain stable. Closed breeding seasons ban fishing during times of reproduction. This protects spawning adults, eggs, and larvae from being caught or disturbed, ensuring successful recruitment of the next generation.

Award up to 2 marks for the explanation of fish quotas:
- Limits total catch / prevents overfishing / maintains sustainable harvesting levels (1 mark).
- Ensures sufficient adult fish survive to breed and maintain future populations (1 mark).

Award up to 2 marks for the explanation of closed breeding seasons:
- Prohibits fishing during spawning times / allows undisturbed reproduction (1 mark).
- Protects young / juvenile fish / eggs, ensuring higher survival rates to recruit into the fishery (1 mark).

Level 3 (5-6 marks):
- Balanced evaluation of the statement with a clear conclusion.
- Explains the benefits of national parks (e.g., preserving large intact ecosystems, preventing habitat fragmentation, legal protection).
- Discusses the limitations (e.g., cost, enforcement challenges, poaching, conflict with local communities).
- Proposes alternative/complementary strategies (e.g., wildlife corridors, ex-situ conservation like seed banks/zoos, community-led conservation, international trade bans like CITES).
- Uses precise environmental management terminology.

Level 2 (3-4 marks):
- Evaluates the statement but may lack balance or a clear conclusion.
- Describes some benefits and limitations of national parks or mentions some alternative strategies.
- May lack detailed examples or specific terminology.

Level 1 (1-2 marks):
- Provides a simple opinion (agree or disagree) with minimal supporting reasons.
- May present points in a list format with little to no development.

Level 0 (0 marks):
- No response or no creditable response.

Level 3 [5–6 marks]
A coherent response is given that develops and supports the candidate's conclusion using relevant details and examples. Indicative content and subject-specific vocabulary are generally used precisely and accurately. Good responses are likely to present a balanced evaluation of the statement.

Level 2 [3–4 marks]
Development and support of the conclusion is evident, though the response may lack some coherence and / or detail. Irrelevant detail may be present. Indicative content and subject-specific vocabulary are used but may lack some precision and / or accuracy. Responses contain evaluation of the statement, but this may not be balanced.

Level 1 [1–2 marks]
The response may be limited in development and / or support. Contradictions and / or irrelevant detail may be present. Indicative content and subject-specific vocabulary may be limited or absent. Responses may lack structure or be in the form of a list. Evaluation may be limited or absent.

Level 0 [0 marks]
No response or no creditable response.

Indicative content:
agree:
- national parks protect large, contiguous habitats necessary for wide-ranging species
- minimizes habitat fragmentation and maintains gene flow
- provides legal frameworks to prevent urban sprawl, mining, logging, or intensive agriculture
- protects entire ecosystems and food webs intact rather than single species
- creates opportunities for ecotourism which funds ongoing conservation

disagree / alternatives are also needed:
- national parks can be difficult and expensive to patrol and police (leading to illegal poaching/logging)
- can cause conflict with local people if they are displaced or lose access to resources
- does not protect migratory species that cross national borders
- climate change and invasive species can still threaten biodiversity within park borders
- ex-situ conservation (such as captive breeding programs, seed banks, and zoos) is vital for species on the brink of extinction
- community-led conservation projects often achieve better local compliance and protection
- wildlife corridors are needed to link separate reserves
- international legislation (like CITES) is required to stop illegal global wildlife trade

Decrease in concentration = 48 - 12 = 36 micrograms per cubic metre. Percentage decrease = (36 / 48) * 100 = 75%.

1 mark for correct working: (48 - 12) / 48 * 100. 1 mark for correct final answer of 75%.

The trend shows a continuous increase in breeding pairs over the six-year period, rising from 14 pairs in 2018 to 54 pairs in 2023.

1 mark for identifying the overall/continuous increasing trend. 1 mark for supporting with correct data from the text (e.g., 14 pairs in 2018 to 54 pairs in 2023).

To describe the trends:
1. State that both birth rate and death rate show an overall decrease over the 30-year period.
2. Quote specific data points for both birth rate (from 34 to 14 per 1000) and death rate (from 12 to 8 per 1000) to support your description.
3. Contrast the rate of decline: birth rate fell by 20 per 1000, which is a much steeper decline compared to the death rate which fell by only 4 per 1000.

- overall trend: both birth rate and death rate decreased [1]
- use of birth rate data: fell from 34 to 14 per 1000 (or decreased by 20 per 1000) [1]
- use of death rate data: fell from 12 to 8 per 1000 (or decreased by 4 per 1000) OR birth rate fell more rapidly than death rate [1]

1. Find the increase in wind energy percentage from 2015 to 2025:
\(30\% - 12\% = 18\%\) (an increase of 18 percentage points).

2. Calculate the percentage increase relative to the original 2015 value:
\(\frac{18}{12} \times 100 = 1.5 \times 100 = 150\%\).

- calculation of increase in percentage points: \(30 - 12 = 18\) [1]
- division by the original 2015 value: \(\frac{18}{12}\) [1]
- correct final answer: 150% [1]

1. Identify the correlation between distance and dissolved oxygen: as distance from the sewage outlet increases, dissolved oxygen increases from 2.1 mg/dm³ to 9.2 mg/dm³.
2. Connect oxygen levels to the abundance of stonefly nymphs: stonefly nymphs increase in number from 0 to 35 because they require high dissolved oxygen levels (they are indicator species for clean, oxygen-rich water).
3. Explain the underlying cause: organic matter in sewage near the outlet is decomposed by aerobic bacteria, which rapidly depletes the dissolved oxygen.

- as distance increases, dissolved oxygen increases / direct relationship between distance and dissolved oxygen [1]
- stonefly nymphs abundance increases as dissolved oxygen increases / stoneflies are sensitive to low oxygen or require high oxygen [1]
- explanation of low oxygen near outlet: decomposition of sewage/organic matter by bacteria uses up oxygen [1]

1. Independent variables like time (Year) are always plotted on the x-axis.
2. Dependent variables like the count (Mammal Population) are plotted on the y-axis.
3. The minimum value of the scale should ideally be 0 (or 40) and the maximum should be at least 120 (e.g., 130 or 140) with regular linear intervals (e.g., 10 or 20 units per major grid division) so that the data from 50 to 120 is spread across more than half the grid height.

- x-axis variable: Year [1]
- y-axis variable: Mammal Population (or number of mammals) [1]
- y-axis scale: linear scale starting at 0 (or up to 40) and ending at 130 or 140 / sensible intervals such as 10 or 20 [1]

Population density is calculated by dividing the total population by the total area: \( \text{Population Density} = \frac{121500}{450} = 270 \) people per km².

1 mark for correct working: \( 121500 / 450 \). 1 mark for correct answer with unit: 270 people per km² (accept people/km² or people per square kilometre).

The increase in volume is \( 16.0 - 12.5 = 3.5 \) million m³. The percentage increase is calculated as: \( \frac{3.5}{12.5} \times 100 = 28\% \).

1 mark for correct calculation of the increase (3.5 million m³) or correct substitution into the percentage increase formula: \( \frac{3.5}{12.5} \times 100 \). 1 mark for the correct answer: 28 (%).

First, find the mass of waste rock: \( 80000 - 2400 = 77600 \) tonnes. Then, calculate the percentage of waste rock: \( \frac{77600}{80000} \times 100 = 97\% \). Alternatively, find the percentage of ore: \( \frac{2400}{80000} \times 100 = 3\% \), so the waste percentage is \( 100\% - 3\% = 97\% \).

1 mark for the correct answer: 97 (%).

Two limitations of pitfall traps:
1. Extreme weather (like heavy rainfall) can fill the trap with water, causing specimens to escape or drown, altering the sample size.
2. Predation can occur inside the trap if active predators are captured alongside smaller prey species, reducing the final count before collection.

Award 1 mark for each valid limitation up to a maximum of 2 marks.
Acceptable answers include:
- Specimen loss due to traps flooding / overflowing during rain.
- Captives may be eaten by predators also caught in the trap.
- Bias towards highly active, ground-dwelling species (inactive species are less likely to fall in).
- Flying or climbing invertebrates can easily crawl or fly out of the trap.

An EIA is a critical planning tool designed to:
1. Identify environmental risks, such as toxic runoff contaminating nearby agricultural water supplies, allowing developers to redesign the project to prevent damage.
2. Formulate mitigation and restoration plans, ensuring the open-pit site can be safely rehabilitated once mineral extraction is complete.

Award 1 mark for each valid reason up to a maximum of 2 marks.
Acceptable answers include:
- To identify and assess potential negative impacts (e.g., water pollution, habitat destruction) before they occur.
- To propose mitigation strategies or land reclamation plans to minimize long-term environmental damage.
- To provide an opportunity for the local community and stakeholders to express concerns and participate in decision-making.
- To evaluate the economic and environmental sustainability of the project.

Population density is low outside the Nile basin because:
1. The hyper-arid desert climate lacks natural aquifers or surface water sources needed to sustain domestic human life.
2. The sandy, nutrient-deficient soils and lack of rainfall prevent agricultural production, meaning people cannot grow crops or raise livestock.

Award 1 mark for each valid reason up to a maximum of 2 marks.
Acceptable answers include:
- Extreme aridity / lack of reliable freshwater supplies.
- Soil is infertile / unsuitable for agriculture.
- Lack of roads, electricity, and basic infrastructure in remote desert regions.
- Lack of industrial employment or trade opportunities away from main river hubs.

The warm wastewater causes thermal pollution, which impacts the stream in two main ways:
1. Warm water has a lower solubility for gases, meaning dissolved oxygen concentrations drop, causing suffocation of sensitive fish species.
2. The increased temperature artificially accelerates the metabolic rates of cold-blooded organisms, increasing their energy and food demands, which can lead to starvation if the food web cannot support it.

Award 1 mark for each explained consequence up to a maximum of 2 marks.
Acceptable answers include:
- Decreased dissolved oxygen levels [1 mark] leading to suffocation / death of fish [1 mark].
- Increased metabolic rates of fish [1 mark] causing food shortages / starvation [1 mark].
- Thermal shock directly killing sensitive species [1 mark] reducing overall aquatic biodiversity [1 mark].
- Promotes rapid growth of warm-tolerant toxic algae / pathogens [1 mark] disrupting the local food web [1 mark].

Mangroves serve as a natural bio-shield by:
1. Dissipating wave energy. As storm surges hit the thick, interconnected root systems of mangroves, the water's speed and height are significantly reduced before reaching villages.
2. Reducing wind velocities. The physical mass of the forest canopy creates friction, slowing down cyclone-force winds.

Award 1 mark for each valid mechanism up to a maximum of 2 marks.
Acceptable answers include:
- Interconnected root systems absorb / dissipate the energy of storm surges.
- The forest canopy acts as a windbreak, reducing high wind speeds.
- Roots trap sediment to prevent severe coastal erosion from strong tidal currents.
- They slow down the inland progression of seawater, reducing flooding depth.

Wet scrubbers work by spraying an alkaline mixture, usually containing lime or limestone, into the path of exhaust gases. The alkaline chemicals chemically react with acidic gases like sulfur dioxide (\(SO_2\)), trapping them in a liquid sludge so they cannot escape into the atmosphere and cause acid deposition downwind.

Award 1 mark for each of the following points:
- Uses an alkaline spray / lime slurry to react with and remove acidic gases / sulfur dioxide (\(SO_2\)) from the exhaust [1 mark].
- Prevents these acidic gases from entering the atmosphere, which significantly reduces the formation of acid rain / deposition [1 mark].

When upwelling ceases:
1. The warm water lacks the nitrate and phosphate nutrients needed for photosynthesis, causing a massive crash in phytoplankton (primary producer) populations.
2. This loss of food travels up the trophic levels; herbivorous anchovies starve and die out, which in turn starves larger predators like seabirds, sea lions, and commercial fish species.

Award 1 mark for each valid impact up to a maximum of 2 marks.
Acceptable answers include:
- Lack of nutrients reduces phytoplankton populations / lowers primary productivity.
- Zooplankton and small herbivorous fish (e.g., anchovies) decline due to a lack of food.
- Higher trophic level predators (e.g., seabirds, sea lions, tuna) starve, die, or are forced to migrate.
- Overall carrying capacity and biodiversity of the marine ecosystem is temporarily reduced.

Soil salinisation harms crops because:
1. Osmotic stress: High concentrations of salt in the soil water lower its water potential below that of the plant roots. Water is drawn out of the plant, or cannot enter, leading to physiological drought and wilting.
2. Ion toxicity: When plants take up the saline water, harmful sodium and chloride ions build up in leaves, disrupting photosynthesis and causing cellular damage.

Award 1 mark for each explained reason up to a maximum of 2 marks.
Acceptable answers include:
- Salt lowers soil water potential [1 mark] making it difficult for roots to absorb water via osmosis / causing physiological drought [1 mark].
- Toxic salt ions (sodium/chlorine) accumulate in plant tissues [1 mark] destroying plant cells / inhibiting photosynthesis [1 mark].
- High salt levels prevent roots from absorbing other essential nutrients [1 mark] leading to severe mineral deficiencies [1 mark].
- Salts degrade soil structure by dispersing clay particles [1 mark] which reduces aeration and water drainage in the root zone [1 mark].

Coastal urban areas offer pull factors such as employment opportunities in developed marine and service sectors, as well as superior public services (healthcare, education) compared to isolated rural villages.

Award 1 mark for each valid reason up to a maximum of 2 marks.
- Accept: employment opportunities / jobs / higher wages.
- Accept: better infrastructure / access to education / access to healthcare / social services.
- Reject: general 'better lifestyle' without qualification.

Excess fertilizer is washed into rivers via surface runoff. This nutrient enrichment (nitrogen) causes rapid growth of algae. When these algae die and decompose, aerobic bacteria consume oxygen, leading to hypoxia and fish kills.

Award 1 mark for each described impact up to a maximum of 2 marks.
- Accept: nutrient enrichment / leaching / runoff leading to eutrophication / algal blooms [1].
- Accept: reduction in dissolved oxygen / hypoxia [1].
- Accept: death of fish / loss of aquatic biodiversity [1].

Open-cast mining requires clearing large areas of topsoil and vegetation (overburden), directly leading to habitat loss. Exposed soil is easily eroded by rainfall, causing siltation in rivers.

Award 1 mark for each valid impact up to a maximum of 2 marks.
- Accept: habitat destruction / deforestation / loss of biodiversity [1].
- Accept: soil erosion / land instability / landslides [1].
- Accept: siltation / pollution of rivers [1].
- Accept: noise pollution / air pollution from dust [1].

By retaining wastewater, the velocity of the flow decreases, which enables gravity to pull sediment and insoluble chemical precipitates out of suspension, leaving cleaner water to flow out of the site.

Award 1 mark for identifying the mechanism and 1 mark for the consequence:
- Retention of water/slowing flow rate to allow gravity settling of particles [1].
- Prevents sediment/toxic metals from entering downstream rivers/habitats [1].

Structural mitigation can involve coastal defenses like sea walls to block rising sea levels/waves, and structural engineering codes to ensure buildings do not collapse under intense wind load.

Award 1 mark for each structural strategy described up to a maximum of 2 marks.
- Accept: construction of sea walls / dykes / storm surge barriers [1].
- Accept: elevated buildings on stilts (to avoid floodwaters) [1].
- Accept: reinforced roofs / wind shutters / cyclone-resistant building codes [1].
- Reject: non-structural methods such as 'early warning systems', 'evacuation plans', or 'hazard mapping'.

Restoration involves replacing the removed rock and soil layers (overburden and topsoil) back into the mining pit, followed by bioremediation or reforestation with native plants to prevent erosion and encourage ecological succession.

Award 1 mark for each valid action up to a maximum of 2 marks.
- Accept: replacing stored overburden / topsoil [1].
- Accept: grading/leveling the land surface [1].
- Accept: replanting native vegetation / reforestation [1].
- Accept: adding fertilizers / treating soil to restore pH [1].

Banning fishing during spawning seasons ensures that breeding adults are not harvested before they can reproduce. This directly increases the recruitment of young fish into the population, boosting stock recovery.

Award 1 mark for the direct mechanism and 1 mark for the biological consequence:
- Prevents fishing during critical breeding / spawning periods [1].
- Allows successful reproduction / recruitment of juvenile fish into the population [1].

To avoid bias, coordinates must be determined randomly using a random number generator. To ensure representativeness, sample sizes must be large and cover all varied sub-habitats where the species might live.

Award 1 mark for each valid suggestion up to a maximum of 2 marks.
- Accept: use a grid system and random number generator (for coordinates) to avoid bias [1].
- Accept: increase the number of sample plots / larger sample size [1].
- Accept: sample in different habitat zones / altitudes / forest types [1].
- Accept: carry out sampling at different times of the year / day [1].

1. Habitat destruction: Piling overburden on natural land clears native vegetation and destroys animal habitats.
2. Siltation of rivers: Rain washes loose sediment from the piles into nearby streams, blocking light and harming aquatic ecosystems.

Award 1 mark for each valid environmental impact up to a maximum of 2 marks.
- habitat loss / destruction of vegetation / loss of biodiversity;
- visual pollution / scarring of the landscape;
- soil erosion / loose sediment washed into rivers (causing siltation);
- dust pollution / air pollution from wind blowing loose particles;
- risk of landslides / collapse of the spoil heaps;
- leaching of toxic minerals / acid mine drainage into soil/water;
[Reject: general pollution without qualification, cost-related answers]

1. Restricting visitor numbers: Implementing a daily quota or permit system ensures that the carrying capacity of the ecosystem is not exceeded.
2. Guided trails / boardwalks: Keeping visitors on designated paths prevents the trampling of plants and soil compaction.

Award 1 mark for each correct method suggested up to a maximum of 2 marks.
- limiting visitor numbers / using permits / capping daily entries;
- zoning / seasonal closures / blocking access to sensitive breeding areas;
- requiring visitors to stay on designated paths / constructing boardwalks;
- employing rangers to monitor and enforce littering and path rules;
- educating visitors through signage or mandatory conservation briefings;
- charging entry fees to fund restoration and protection programs;
[Reject: banning all tourism / closing the entire park (as the context is managing ecotourism)]

1. Lay the tape measure out as a transect line at a right angle (90 degrees) to the trail. 2. Place the quadrat at regular intervals along the tape measure (e.g., every 1 or 2 meters). 3. Record the percentage cover or count the number of plants of the target species in each quadrat.

Award 1 mark for each correct point up to a maximum of 3 marks: - Lay the tape measure out as a transect line at a right angle (90 degrees) to the trail [1] - Place the quadrat at regular intervals along the tape measure (e.g. every 1 or 2 meters) [1] - Estimate and record the percentage cover / count the number of plants in each quadrat [1]

1. Take samples at fixed, measured distances upstream and downstream of the mine discharge point. 2. Use a calibrated digital pH probe / pH meter (to ensure accuracy). 3. Repeat measurements at each location (e.g., three times) and calculate a mean average value.

Award 1 mark for each correct point up to a maximum of 3 marks: - Take samples at fixed distances upstream and downstream of the mine discharge point [1] - Use a calibrated digital pH probe / pH meter [1] - Repeat measurements at each location and calculate a mean / average value [1]

1. Survey at multiple different locations in the local community (not just at the resort entrance where bias towards tourists/resort workers is high). 2. Increase the sample size to a larger number (e.g., 50 or 100 people). 3. Survey at different times of day / different days of the week (to capture a wider demographic, including working people).

Award 1 mark for each correct point up to a maximum of 3 marks: - Survey at multiple different locations in the local community (not just at the resort entrance) [1] - Increase the sample size to a larger number (e.g., 50 or 100 people) [1] - Survey at different times of day / different days of the week [1] - Use a systematic or random sampling method rather than opportunity sampling [1]