2026 Cambridge IGCSE Environmental Management (0680) Practice Paper with Answers

Population density is calculated using the formula:

\[ \text{Population density} = \frac{\text{Total population}}{\text{Land area in }\text{km}^2} \]

\[ \text{Population density} = \frac{84\ 000}{1200} = 70\text{ people per km}^2 \]

70 (people per km\(^2\));

The third largest sector represents \( 15\% \) of the electricity generated. According to the data in the table, \( 15\% \) corresponds to wind energy.

wind / wind power / wind energy;

During hydraulic fracturing, a mixture of water, sand, and chemicals is pumped down a well at extremely high pressure. This pressure forces fractures and micro-cracks to form and propagate within the deep, impermeable shale formations, allowing the trapped natural gas (methane) or oil to flow freely into the wellbore for extraction.

Award 1.5 marks for a complete description:
- Fluid is forced deep underground at high pressure to crack / fracture impermeable shale rock [1];
- Allows trapped natural gas / petroleum to escape / flow into the wellbore [0.5].

Reject: fracturing permeable rock layers.

When high pressure fractures the deep shale rock, the newly formed fissures would naturally snap shut under the immense weight of overlying rock once the pumping pressure stops. Sand grains (proppants) enter these cracks and physically hold (prop) them open, maintaining continuous pathways for gas or oil to migrate to the extraction pipe.

Award 1.5 marks for an explanation covering:
- Sand particles enter the newly created cracks / fissures [0.5];
- Holds / props the fractures open when hydraulic pressure drops [0.5];
- Maintains a porous channel for hydrocarbons / gas to flow out continuously [0.5].

Water is pumped deep underground through injection wells into hot geothermal rock reservoirs. The thermal energy heats the water into high-pressure steam (or hot pressurised brine), which ascends through production wells. The kinetic force of this expanding steam drives a turbine, spinning a generator to produce electrical energy before the cooled water is condensed and reinjected.

Award 1.5 marks for the technical energy conversion process:
- Water / fluid is heated by hot underground rocks to generate steam [0.5];
- Expanding high-pressure steam drives / spins a turbine [0.5];
- The rotating turbine turns a generator to produce electrical current [0.5].

A closed loop of subterranean pipes circulates an antifreeze fluid that absorbs constant low-grade thermal energy from the ground. This warmed fluid passes through a heat exchanger (evaporator) where the heat evaporates a refrigerant. An electrically driven compressor compresses the gaseous refrigerant, raising its temperature significantly. A condenser then releases this concentrated heat into the interior heating system (e.g., underfloor heating or radiators).

Award 1.5 marks for explaining the heat transfer cycle:
- Fluid circulating in underground loops absorbs ambient thermal energy from the soil [0.5];
- A compressor compresses a refrigerant gas, increasing its temperature and pressure [0.5];
- The concentrated heat is transferred via a heat exchanger into the building heating system [0.5].

Terracing alters the topography of steep slopes by creating a series of flat, stepped platforms. This reduces the steepness of the slope face, slowing the velocity of water running down the hillside. Consequently, surface run-off is minimized, infiltration into the soil profile increases, and the detachment and transport of fertile topsoil are greatly reduced.

Any two from:
- breaks steep slope into flat steps / benches / horizontal platforms [1];
- reduces the speed / velocity / momentum of surface run-off [1];
- increases water infiltration / percolation into the soil [1];
- traps / retains water and detached sediment on the terraces [1];
- prevents the formation of rills and gullies down the slope [1].
Reject: completely stops all rainfall.

When fields are ploughed up and down a slope, the furrows act as natural channels that accelerate water run-off and cause rill and gully erosion. In contrast, contour ploughing follows the natural contours of the land at right angles to the slope gradient. The resulting ridges and furrows act as physical barriers that trap water and sediment, slowing run-off velocity and encouraging infiltration.

Any three from:
- ploughing is done across the slope / along lines of equal elevation / perpendicular to the slope gradient [1];
- furrows and ridges act as mini-barriers / dams to catch water [1];
- slows down / reduces the velocity / volume of surface run-off [1];
- allows more time for water to infiltrate / soak into the ground [1];
- prevents run-off from concentrating into channels / rills / gullies [1];
- holds / prevents detachment of fertile topsoil [1].

Continuous vegetation cover protects soil through multiple mechanisms: the canopy and crop residues act as an umbrella that intercepts falling rain to reduce droplet impact (splash erosion), while the dense root systems physically anchor soil aggregates together, making them resistant to detachment by wind or sheet wash.

Two distinct explained ways for [1] mark each (mechanism + effect):
- foliage / leaves / stubble intercepts falling raindrops / absorbs kinetic energy [1] which prevents splash erosion / dislodging of soil particles [1];
- root networks hold / bind soil particles together [1] improving soil structure / preventing soil being washed or blown away [1];
- vegetation / organic residue increases surface roughness / friction [1] which slows down surface run-off / traps moving sediment [1];
- plants act as a physical barrier against wind [1] reducing wind velocity at ground level / preventing wind lift [1].
[Max 2 marks total: award 1 mark per valid explained point, up to 2].

(a) Multipurpose dams provide several functions beyond irrigation and hydro-electric generation, including domestic potable water supply, industrial cooling/manufacturing water, flood regulation, inland aquaculture, and recreational activities such as boating.

(b) Upstream: The impoundment of water floods existing terrestrial ecosystems, causing loss of forest/farmland habitats and anaerobic decomposition of submerged organic matter, releasing greenhouse gases (methane).
Downstream: The barrier blocks natural sediment transport, depriving agricultural floodplains of nutrient-rich silt, and alters downstream flow regimes while obstructing migratory aquatic organisms (such as fish moving upstream to spawn). (1.5 marks for both upstream and downstream explained clearly; award 1 mark for one fully developed impact and 0.5 mark for the second partial/identified impact).

(a) [1 mark max]
• domestic / municipal / potable water supply;
• flood control / flood prevention;
• aquaculture / commercial fishing in the reservoir;
• leisure / recreation / water sports / tourism;
• navigation / transport of goods;
• industrial water supply;
[Reject: 'generates electricity' / 'irrigation' as they are given in the stem]

(b) [1.5 marks max]
Upstream impact [1 mark max]:
• flooding / drowning of terrestrial habitats / loss of terrestrial biodiversity;
• decomposition of submerged biomass / release of greenhouse gases / methane;
• accumulation of sediment in the reservoir;

Downstream impact [1 mark max]:
• reduced silt / nutrient replenishment on downstream floodplains;
• disrupted migration of fish / barrier to breeding cycles;
• altered water temperature / reduced river discharge affecting downstream aquatic organisms;
• increased coastal / riverbed erosion due to trapped sediment;
[Maximum 1.5 marks for part (b): 1 mark for one fully explained impact and 0.5 mark for the other]

(a) Silt deposits settle at the bottom of the reservoir, decreasing its total water holding capacity. This reduces the amount of water available for seasonal storage, domestic supply, and irrigation, as well as reducing the hydraulic head available for hydro-electric power generation. Additionally, suspended sediment can cause mechanical abrasion and wear on turbine blades.

(b) Catchment management strategies to reduce siltation focus on preventing soil erosion upstream: (1) Afforestation or maintaining vegetation cover on valley slopes to increase water infiltration, bind soil particles with root networks, and intercept rainfall; (2) Contour ploughing or terracing on agricultural slopes to slow surface run-off and prevent rill/gully erosion from washing sediment into feeder streams.

(a) [1 mark max]
• reduces the water holding / storage capacity of the reservoir;
• reduces volume of water available for dry season supply / irrigation / HEP;
• abrasive sediment causes mechanical wear / damage to hydro-electric turbine blades;
• blocks intake pipes / water outlets;

(b) [1.5 marks max]
Any two strategies with brief description [award 1 mark for one fully described strategy and 0.5 mark for the second]:
• afforestation / planting trees on slopes / maintaining riparian vegetation [1] to bind soil with roots / intercept rainfall / reduce surface run-off [0.5];
• contour ploughing / terracing on hillside farms [1] to create barriers across slopes / slow down surface run-off [0.5];
• construction of check dams / sediment traps in feeder streams [1] to catch silt before it enters the main reservoir [0.5];
• establishing grass strips / buffer zones along riverbanks [1] to filter out eroded soil particles [0.5];
• managing grazing / avoiding overgrazing in the watershed [1] to keep soil covered by pasture [0.5];

(a)
Decrease in Zone C = \(85 - 17 = 68\)
Percentage decrease = \(\frac{68}{85} \times 100 = 80\%\)

(b)
Mosquito larvae live in stagnant aquatic habitats and cannot fly or bite. Destroying larvae prevents them from maturing into adult female Anopheles mosquitoes, thus disrupting the life cycle and stopping the transmission of the Plasmodium parasite to humans.

(a) [2 marks]
M1 for correct calculation of change: \(85 - 17 = 68\) OR \(\frac{68}{85}\) OR \(\frac{17}{85} \times 100 (= 20\%)\);
A1 for correct final answer: \(80\) / \(80\%\);

(b) [1 mark]
1 mark for: prevents larvae maturing/developing into adult (flying/biting) mosquitoes / reduces adult mosquito population / stops vector from transmitting the (Plasmodium) parasite to humans / breaks the mosquito reproductive cycle;

(a) There is a positive relationship / higher rainfall leads to higher cases, but with a delay or time lag (rainfall peaks in March at 240 mm, whereas malaria cases peak in April/May at 310 cases).

(b)
1. High rainfall creates temporary pools of stagnant water; it takes 1 to 2 weeks for Anopheles eggs to hatch, develop through larval and pupal stages, and emerge as adult mosquitoes.
2. Once an adult female mosquito bites an infected person, the Plasmodium parasite requires an incubation period inside both the mosquito and the human host before clinical symptoms develop and cases are diagnosed.

(a) [1 mark]
1 mark for: positive relationship / as rainfall increases, malaria cases increase (and then decrease as rainfall drops) / cases follow rainfall with a time lag / peak in cases occurs after peak in rainfall;

(b) [2 marks]
Any two from:
- stagnant water accumulates / persists after heavy rain to provide breeding grounds;
- time needed for mosquito eggs to hatch / larvae to develop into adult biting mosquitoes / life cycle takes several days/weeks;
- incubation period of the (Plasmodium) parasite inside the mosquito;
- incubation period of the parasite inside the human body / time before symptoms show and are diagnosed/recorded;

[Max 2 marks for part (b)]

(a) The biological control method is introducing predatory/larvae-eating fish (Gambusia) to feed on mosquito larvae in ponds.

(b)
1. Mosquitoes cannot develop genetic resistance to physical removal of their habitat, whereas they frequently develop resistance to chemical insecticides.
2. Environmental management does not release toxic chemicals into ecosystems, preventing bioaccumulation, water pollution, and harm to non-target beneficial species.

(a) [1 mark]
1 mark for: larvae-eating fish / stocking ponds with fish / Gambusia;

(b) [2 marks]
Any two from:
- vectors/mosquitoes cannot develop resistance (to water removal);
- no toxic chemicals entering water bodies / no chemical pollution / avoids bioaccumulation/biomagnification;
- does not harm non-target organisms / beneficial insects / wildlife;
- long-term / permanent reduction in breeding sites / cost-effective in the long term compared to repeated chemical purchasing;

[Max 2 marks for part (b)]

(a) The rain-filled tyre ruts present the highest risk because they contain the highest concentration of mosquito larvae (\(64\text{ per m}^2\)) and are located nearest to human residences (\(15\text{ m}\)), maximising the likelihood of adult mosquitoes biting nearby residents.

(b) Two physical modifications:
1. Infilling depressions, tyre ruts, and potholes with soil or gravel to prevent rainwater accumulation.
2. Regrading or clearing drainage ditches to ensure water flows freely, preventing stagnant pools from forming.

(a) [1 mark]
1 mark for: rain-filled tyre ruts with reason referring to highest larvae density / \(64\text{ per m}^2\) AND closest to houses / \(15\text{ m}\);

(b) [2 marks]
Any two from:
- filling in tyre ruts / potholes / hollows with soil/gravel/sand;
- grading / clearing drains to keep water flowing / prevent stagnation;
- covering / fitting lids to water storage tanks / reservoirs;
- removing artificial containers / discarded tyres / empty cans;
- vegetation clearance around water margins to expose water to sunlight/predators;

[Max 2 marks for part (b)]

(a) Resistance increases continually over the eight years, rising from 4% in Year 0 to 72% in Year 8 (an overall increase of 68 percentage points).

(b) Long-sleeved clothing provides a physical barrier that stops mosquitoes from piercing human skin to feed on blood. Insect repellents deter or disguise human scent, preventing the mosquito from landing. Because these methods do not rely on killing the mosquito via toxic insecticides, genetic resistance to pesticides does not reduce their protective efficacy.

(a) [1 mark]
1 mark for: resistance increases over time / increases from 4% to 72% / increases by 68% (allow rapid / continuous increase);

(b) [2 marks]
1 mark for: long clothing acts as a physical barrier / blocks mosquito access to skin/blood meal;
1 mark for: repellent deters/drives away mosquitoes / masks human scent / prevents landing / these methods do not depend on killing the insect with toxins / resistance does not overcome a physical barrier;

[Max 2 marks for part (b)]

Marine organisms take up dissolved carbon dioxide/carbonate to form calcium carbonate shells or skeletons. Over time, these sediments undergo sedimentation, compaction, and cementation on the sea floor to form limestone, locking carbon out of the active atmospheric cycle.

Any two from:
- Marine organisms/corals/molluscs use dissolved carbon (dioxide)/carbonate to build shells/skeletons;
- Deposition/sedimentation/accumulation of shells and skeletons on the seabed/ocean floor;
- Compaction and cementation / lithification into sedimentary rock / limestone;
- Carbon remains trapped/locked in the rock for geological timescales / millions of years.

Methods include biological capture (reforestation/afforestation/wetland restoration) where atmospheric carbon is stored in plant biomass/soil, and technological carbon capture and storage (CCS) where carbon dioxide is trapped from flue gases or direct air capture and injected into deep rock stores.

Any two methods with brief description [1 mark per paired method and mechanism, max 2]:
- Reforestation / afforestation / planting trees [1] -> takes up CO2 via photosynthesis / stores carbon in biomass/wood [1];
- Carbon capture and storage (CCS) / direct air capture [1] -> CO2 is compressed and injected into porous rocks / depleted aquifers / geological formations [1];
- Soil carbon sequestration / biochar addition [1] -> locks carbon into the soil structure [1].

Permeable sandstone acts as the reservoir rock because pore spaces allow carbon dioxide to be injected and stored. The impermeable shale acts as a cap rock/seal directly above the reservoir to stop the gas from migrating upwards to the surface.

1 mark for role of sandstone, 1 mark for role of shale:
- (Sandstone/permeable rock) provides pore spaces/voids to store/hold the injected carbon dioxide / allows gas to enter/flow [1];
- (Shale/impermeable rock) acts as a cap rock/seal to trap gas / prevent CO2 from leaking/escaping to the surface [1].

(a) The correct word equation is: carbon dioxide + water -> glucose + oxygen. (b) Abiotic factors that can limit the rate of photosynthesis include light intensity, temperature, or water availability.

(a) carbon dioxide + water -> glucose + oxygen [1]
(b) Any one from: light (intensity) / temperature / water (availability) / soil moisture [1]
Reject: biotic factors, oxygen, glucose.

Metamorphism occurs when heat and pressure recrystallise the calcite in limestone to form marble. If rocks melt into magma at subduction zones, thermal breakdown releases carbon as carbon dioxide gas, which vents into the atmosphere during eruptions.

1 mark for transformation into marble, 1 mark for release during volcanic activity:
- (Limestone to marble) subject to (intense) heat and/or pressure (without melting) / undergoes recrystallisation / metamorphism [1];
- (Magma/eruption) carbon is released (as carbon dioxide / CO2 gas) into the atmosphere [1].

Bioremediation uses living organisms to decontaminate land. Specific bacteria or fungi can metabolise organic pollutants or immobilise heavy metals, while selected hyperaccumulating plants take up toxic metal ions from the soil through their root systems (phytoremediation). As contaminant levels decline, organic matter and soil microflora are re-established, improving soil structure and fertility.

Any three from:
• use of living organisms / bacteria / fungi / plants / vegetation;
• organisms absorb / take up / metabolise / neutralise / immobilise toxic heavy metals / contaminants;
• improves organic content / soil structure / aeration as organisms grow / decay;
• reduces toxicity so subsequent plant growth / natural succession can take place;
• avoids the need for chemical treatment / physical removal of soil;

[Total: 3 marks]

Sanitary landfills require engineered barriers to contain pollutants. An impermeable clay or synthetic geo-membrane lining is laid across the base and sides to stop toxic liquid (leachate) from infiltrating into surrounding aquifers. Perforated collection pipes collect leachate at the bottom for treatment. Gas collection wells capture methane generated by anaerobic decomposition of organic waste, preventing explosions and greenhouse gas emissions.

One mark for each distinct feature with its linked protective function (max 3):
• impermeable / clay / plastic / geomembrane liner (1) to prevent leachate / toxic liquid entering groundwater / aquifers (1);
• leachate collection pipes / sumps / treatment system (1) to remove and treat liquid run-off (1);
• methane / gas extraction pipes / wells / flares (1) to safely vent / capture gas / generate electricity / prevent explosion / reduce greenhouse emissions (1);
• top cap / impermeable soil / clay cover (1) to prevent rainwater infiltration / keep pests away / contain odours (1);
• groundwater monitoring boreholes / test wells (1) to detect early leakage of contaminants (1);

[Total: 3 marks]

Economic instruments change industrial and consumer behaviour. A landfill tax acts as a financial deterrent against throwing away reusable materials, making disposal uneconomical. Subsidies provide direct financial support to recycling facilities, lowering production costs for secondary refined metals. Consequently, demand for raw mining decreases, extending the lifetime of finite mineral deposits and conserving energy.

Any three from:
• landfill tax increases the financial cost of disposing of materials / acts as a deterrent against throwing away metals;
• encourages manufacturers / consumers to reduce waste / reuse materials / recycle;
• subsidies reduce operating costs / increase profitability of metal recycling facilities;
• recycled / secondary metals become cheaper / more competitive than newly mined ores;
• reduces the demand / rate of extraction for finite / virgin mineral ores;
• conserves non-renewable reserves for future generations;

[Total: 3 marks]

Mine site restoration begins by backfilling the excavated void using the overburden rock that was stripped and stored during mining. The land is re-contoured and graded to prevent mass movement and allow safe drainage. The original topsoil layer is reapplied and enriched with fertilisers or compost to restore fertility. Finally, vegetation (grasses and native trees) is planted to anchor the soil, prevent erosion, and create habitats.

Any three from:
• backfilling / filling the open pit / void with stored overburden / waste rock;
• re-grading / reprofiling slopes / contouring land to prevent landslides / ensure safe stability / drainage;
• spreading / replacing the stored topsoil / adding compost / fertilisers / soil improvers;
• planting vegetation / native grasses / shrubs / tree planting to stabilise soil / prevent erosion;
• safety testing / monitoring for toxic runoff / subsidence / mine gases before public access;

[Total: 3 marks]

Bioremediation offers an environmentally sensitive in situ solution: it does not require heavy machinery to haul away tons of soil to landfill, preserving soil structure at a lower financial cost. However, biological processes are slow, often requiring months or years to achieve regulatory standards, and microorganisms may become inactive if ambient temperatures, aeration, or toxin concentrations are unfavourable.

Three points required, with at least one benefit and at least one limitation:

Benefits (max 2):
• lower cost / cheaper than heavy excavation and transport to landfill;
• treats / breaks down pollutants in situ / does not simply transfer waste to another site;
• causes less habitat destruction / preserves existing soil structure / landscape;
• environmentally friendly / uses natural biological processes;

Limitations (max 2):
• takes a long time / slower process than physical removal;
• effectiveness depends on environmental factors (e.g. temperature / soil moisture / pH / oxygen levels);
• very high pollutant concentrations may be toxic to / kill the microorganisms;
• may not completely eliminate all types of toxic residues / heavy metals;

[Total: 3 marks]

(i) Percentage increase = \(\frac{\text{Final value} - \text{Initial value}}{\text{Initial value}} \times 100\)
$$\text{Increase} = 1880 - 1570 = 310\text{ ppb}$$
$$\text{Percentage increase} = \frac{310}{1570} \times 100 = 19.745\dots \approx 19.7\%$$

(ii) Two valid anthropogenic sources of methane:
1. Pastoral farming/livestock production (e.g. digestive processes/enteric fermentation of ruminants).
2. Intensive rice paddy cultivation (anaerobic decomposition by bacteria in waterlogged soil).
3. Landfill disposal of organic waste decomposing anaerobically.
4. Extraction, refining, and leakages during natural gas/petroleum mining.

(i) [2 marks total]
M1: Correct method: \(\frac{1880 - 1570}{1570} \times 100\) or \(\frac{310}{1570} \times 100\) ;
A1: 19.7 (%) [allow 19.75, reject 20 without working] ;

(ii) [2 marks total]
Award 1 mark per valid human activity (max 2):
- Livestock / cattle farming / pastoral agriculture (methane from digestion) ;
- Wet / flooded rice cultivation / paddy fields ;
- Landfill waste decomposition (anaerobic conditions) ;
- Coal mining / petroleum extraction / natural gas leakages / fracking ;
- Wetland drainage / biomass burning ;

(a) Graph conventions for Cambridge IGCSE Environmental Management:
- Axes correctly orientated and fully labelled with quantity and unit: 'Decade' on the x-axis and 'Temperature anomaly / °C' on the y-axis.
- Suitable linear scale chosen using more than half of the provided grid along both axes.
- All data coordinates plotted accurately within ±0.5 small square.
- Plots connected with a continuous ruled line from point to point or a smooth curve.

(b) Description of trends:
- Overall continuous upward trend / positive change from +0.10 °C to +0.98 °C.
- Rate of warming is increasing / steeper rise in later decades (e.g. +0.36 °C increase between 2001–2010 and 2011–2020 compared to +0.16 °C between 1971–1980 and 1981–1990).

(a) [3 marks max]:
- Both axes labelled with variable and unit (Decade on x-axis, Temperature anomaly / °C on y-axis) ;
- Linear and sensible scale using \(\ge 50\%\) of grid in both directions ;
- Accurate plotting of coordinates (\(\pm 0.5\) small square) ;
- Points neatly connected with straight ruled lines or smooth curve ;

(b) [1 mark]:
- Temperature anomaly increases continuously / warming accelerates in later decades / quantitative support (e.g. increased by 0.88 °C overall) ;

1. Combustion of coal, oil, and natural gas produces carbon dioxide (and other greenhouse gases), raising their atmospheric concentration in the troposphere.
2. Incoming shortwave solar radiation penetrates the atmosphere and warms the Earth's surface.
3. The Earth emits longwave infrared (thermal) radiation back towards space.
4. Elevated levels of greenhouse gases absorb more of this outgoing infrared radiation.
5. The gases re-radiate thermal energy in all directions, including back toward Earth's surface, trapping additional thermal energy and driving an enhanced greenhouse effect.

Award 1 mark for each valid point (max 4):
- Combustion of coal / oil / gas releases \(\text{CO}_2\) / greenhouse gases into the troposphere ;
- Concentration of greenhouse gases increases in the atmosphere ;
- Shortwave solar radiation passes through the atmosphere to warm Earth's surface ;
- Earth's surface radiates longwave / infrared radiation outwards ;
- Increased greenhouse gas molecules absorb outgoing longwave / infrared radiation ;
- Heat energy is re-emitted in all directions / back to Earth's surface, increasing atmospheric temperatures ;
[Reject 'trapping sunlight' / 'ozone layer damage']

(a) Direct environmental impacts of sea-level rise:
- Permanent or regular inundation/flooding of coastal wetlands, mudflats, and low-lying agricultural plains.
- Intrusion of saline water into coastal groundwater stores/aquifers and estuaries, degrading freshwater supplies.
- Increased rate of shoreline erosion and loss of beach/cliff stability.

(b) Mechanism of ocean acidification:
- Excess \(\text{CO}_2\) in the atmosphere dissolves into ocean surface water.
- It reacts with water (\(\text{H}_2\text{O}\)) to form carbonic acid (\(\text{H}_2\text{CO}_3\)), which dissociates to release hydrogen ions (\(\text{H}^+\)), decreasing ocean pH.
Impact:
- Reduces availability of carbonate ions needed by calcifying organisms (e.g. corals, shellfish) to build calcium carbonate structures, leading to coral bleaching/breakdown of reefs and weakening of marine food chains.

(a) [2 marks max]:
Award 1 mark for each valid consequence:
- Flooding / submergence of low-lying land / mangrove ecosystems ;
- Saltwater intrusion into freshwater aquifers / rivers / agricultural soils ;
- Increased coastal erosion / cliff retreat ;
- Loss of terrestrial / coastal nesting habitats ;

(b) [2 marks max]:
- Explanation: \(\text{CO}_2\) dissolves in seawater to produce carbonic acid / releases hydrogen ions / lowers ocean pH [1] ;
- Impact: Corals / shellfish unable to build calcium carbonate shells/skeletons OR coral bleaching OR disruption to marine food chains [1] ;

(a) Role of AI in energy efficiency:
- Smart building management: AI monitors occupancy and weather forecasts to control air conditioning, heating, and ventilation automatically, cutting wasted power.
- Smart grid optimisation: AI algorithms predict peak energy demand, balance loads between renewable sources (solar, wind) and battery storage, and reduce transmission losses.
- Traffic flow optimisation: AI adjusts traffic light sequences to minimise vehicle idling and congestion emissions.

(b) Agricultural adaptation strategies:
- Introducing drought-resistant, heat-resistant, or salt-tolerant crop cultivars / GMOs.
- Implementing efficient water management: precision drip irrigation, contour bunding, or rainwater storage.
- Altering cropping calendars: adjusting sowing and harvesting dates to align with shifting wet and dry seasons.
- Shifting to agroforestry or protected cultivation (greenhouses/hydroponics) to buffer against extreme heat and storms.

(a) [2 marks max]:
Award 1 mark per valid point (max 2):
- AI monitors/optimises energy use in smart buildings (e.g., automated heating/cooling/lighting) ;
- Optimises electricity distribution across smart grids / manages renewable supply & battery storage ;
- Optimises traffic management to reduce vehicle congestion and idle fuel consumption ;

(b) [2 marks max]:
Award 1 mark for each described adaptation strategy (max 2):
- Use of drought-tolerant / heat-tolerant / salinity-resistant crop varieties or GMOs ;
- Installing drip irrigation / rainwater harvesting to secure water during prolonged dry periods ;
- Adjusting planting / harvesting dates to match altered rainfall patterns ;
- Agroforestry / shaded farming to reduce evapotranspiration and soil temperature ;

Technological solutions offer major mechanisms for decarbonisation: artificial intelligence optimizes electrical grid distribution, improves renewable forecasting, and identifies energy inefficiencies in industry; renewable electricity generation (solar, wind, hydroelectric) replaces fossil fuels, cutting carbon dioxide emissions from power stations; carbon capture and sequestration can remove carbon dioxide from point sources. However, technology faces limitations: high capital costs, resource extraction footprints (e.g. lithium and rare earth mining), and grid transition delays. Conversely, behavioural changes are essential: shifting towards plant-based or lower-trophic-level diets significantly reduces agricultural methane (from ruminant livestock) and nitrous oxide emissions while cutting deforestation for pasture; decreasing consumer demand reduces embodied emissions from manufacture and international transport; family planning choices and energy conservation directly reduce per capita resource strain. Therefore, reliance on technology alone is insufficient; integrated mitigation combining advanced technology with widespread lifestyle adaptation is necessary to meet climate goals.

Level 3 (5–6 marks):
A balanced, detailed discussion evaluating both technological advancements and lifestyle/behavioural changes. Clear understanding of specific greenhouse gas reductions (e.g. CO2 from energy, CH4 from livestock) with accurate terminology. Reaches a reasoned, well-supported conclusion.

Level 2 (3–4 marks):
A developed discussion addressing both technological and behavioural strategies, but may be unbalanced or lack specific technical detail regarding mechanisms and limitations.

Level 1 (1–2 marks):
Limited response that offers basic statements or lists examples of technology or green habits without evaluating their feasibility or comparing both sides.

Indicative content points for credit:
- Technological benefits: AI for smart grid management; renewable energy (solar, wind) displacing fossil fuel combustion; battery storage; electric vehicles.
- Technological limitations: high investment costs; finite mineral extraction impacts; time lag for infrastructure deployment.
- Behavioural/dietary roles: adopting plant-rich diets lowers enteric methane (CH4) from cattle; reduced food waste; choosing public transit or active travel; reducing consumerism.
- Concluding judgement: technology is vital but cannot succeed alone without public engagement and demand-side reductions.

(i) Population density = \(\frac{\text{Total Population}}{\text{Total Land Area}}\)
Population density = \(\frac{345\,000}{1\,500} = 230\text{ people per km}^2\)

(ii) Coastal lowlands offer flat/gentle terrain which makes construction of housing and transport infrastructure easier, and fertile soils along river plains facilitate intensive food production.

(i) Correct calculation: \(345\,000 \div 1\,500 = 230\) [1]; Correct unit: people per \(\text{km}^2\) / people/\(\text{km}^2\) [1];

(ii) Any one valid physical reason [1]: flat/gentle land relief (easier construction / mechanisation); reliable water supply from rivers/estuaries; fertile alluvial soil for crop cultivation; accessible maritime trade/transport routes. Reject: generic references without physical context.

(i) Natural increase per \(1\,000\) = \(34 - 9 = 25\text{ per }1\,000\).
Natural increase rate (\(\%\)) = \(\frac{25}{1\,000} \times 100 = 2.5\%\).

(ii) Push factors are negative conditions forcing people to leave rural areas, including agricultural unemployment/low income, loss of land fertility/drought, and limited access to healthcare or higher schooling.

(i) Natural increase calculation: \(34 - 9 = 25\) per \(1\,000\) [1]; Conversion to percentage: \(2.5\%\) [1];

(ii) Any two valid rural push factors [1 mark each]: lack of jobs / low wages; crop failure / soil degradation / drought; poor access to healthcare / hospitals; limited education opportunities; lack of clean piped water / electricity; natural disasters destroying farmland. Reject: pull factors (e.g. city nightlife, better urban jobs).

Effective pre-disaster cyclone management includes:
1. Issuing clear early warnings using meteorological tracking and telecommunication to inform the public.
2. Evacuating vulnerable coastal populations along planned escape routes to designated cyclone shelters on elevated ground.
3. Pre-positioning emergency supplies (potable water, non-perishable food, medical kits) in storm-proof community shelters.

Award [1 mark] for each distinct valid pre-disaster strategy (up to 3 marks):
- Issuing early warnings / siren systems / media broadcasts about storm track and timing;
- Mandatory or organized evacuation of low-lying / coastal zones to higher ground;
- Opening purpose-built emergency cyclone shelters / storm shelters;
- Stockpiling emergency relief items (drinking water, medicines, dry food);
- Boarding up windows / securing loose outdoor structures / sandbagging levees;
- Enforcing maritime fishing bans / ordering boats to safe harbor.
Reject: post-disaster strategies (e.g., searching for survivors, rebuilding homes).

(i) Cholera is a water-borne bacterial disease spread via the fecal-oral route. Floods breach pit latrines and sewage pipes, washing human excreta containing Vibrio cholerae directly into open wells, surface streams, and municipal drinking water pipes.
(ii) Treating collected water by boiling it to boiling point or adding chlorine tablets kills the bacteria before consumption.

(i) [2 marks total]:
- Floodwaters breach/overflow latrines / sewers / wastewater infrastructure [1];
- Pathogens/sewage contaminate shallow wells / open water supplies / drinking water consumed by residents [1];

(ii) [1 mark for one valid method]:
- Boiling the water (for at least 1 minute);
- Chlorination / adding chlorine tablets / household bleach drops;
- Use of ceramic / membrane filtration units combined with disinfection.
Reject: simple mesh straining alone (does not remove bacteria).

(i) A wide base represents a high crude birth rate and a large proportion of young children in the population.
(ii) Challenges include heavy government spending on primary and secondary education (building schools, training teachers), high healthcare burden for childhood immunisation and maternal care, and a high dependency ratio where fewer working adults must economically support many children.

(i) High birth rate / high fertility rate / large proportion of children [1].

(ii) Any two socio-economic challenges [1 mark each]:
- High expenditure / pressure on schooling / education infrastructure / teacher shortages;
- Increased healthcare costs for infant care, vaccination, and maternal health;
- High dependency ratio / smaller tax base relative to dependent population;
- Future strain on job market / risk of youth unemployment when children reach working age;
- Risk of food shortages / pressure on family resources to feed large households.

(i) Earthquake-resistant buildings can incorporate base isolators (rubber and steel bearings) to absorb ground vibrations, flexible steel cross-bracing to prevent lateral structural collapse, or reinforced concrete foundations.
(ii) Land-use zoning prevents the construction of high-occupancy buildings (schools, hospitals, housing) on geologically unstable terrain such as soft reclaimed soils prone to liquefaction or steep hillsides prone to landslides.

(i) Any two engineering features [1 mark each]:
- Base isolation / rubber/lead bearings / dampers under foundations;
- Reinforced cross-bracing / shear walls / flexible steel frames;
- Deep foundations anchored into solid bedrock;
- Counterweights / tuned mass dampers on top floors;
- Automatic shut-off valves for gas and electricity to prevent post-quake fires.

(ii) Explanation of land-use zoning [1 mark]:
- Restricting building on active fault lines, unconsolidated sediment (liquefaction zones), or steep slopes liable to landslides / allocating open parkland in high-risk zones to prevent building collapse onto people.

To mitigate agricultural drought impacts:
1. Transitioning from flood irrigation to efficient micro-irrigation (drip systems) delivers water directly to plant roots with minimal evaporation.
2. Planting drought-resistant forage/crop varieties ensures livestock feeding during dry spells.
3. Building small-scale water-retaining structures such as bunds, check dams, or subsurface sand dams captures intermittent runoff for emergency herd watering.

Award [1 mark] for each valid management strategy (up to 3 marks):
- Upgrading to drip irrigation / micro-sprinklers / efficient watering methods;
- Rationing water supplies / implementing hosepipe bans / regulating groundwater extraction;
- Constructing bunds / check dams / rainwater harvesting storage tanks;
- Cultivating drought-tolerant crops / fodder species;
- Destocking / managed culling of livestock to reduce overgrazing;
- Distributing emergency feed and tankered water supplies to affected farmers.

(i) Educating females delays the age of marriage/first childbearing, directly shortening the reproductive window. Educated women are also better informed about reproductive health, have higher career aspirations, and are more empowered to use modern contraception.
(ii) Educational interventions require significant capital investment, take a generation to demonstrate measurable fertility declines, and may encounter resistance in deeply traditional patriarchal communities.

(i) Any two valid mechanisms linking female secondary education to lower birth rates [1 mark each]:
- Delays average age of marriage / increases age of first pregnancy;
- Increases knowledge of and access to modern contraception / family planning;
- Opens formal employment / career opportunities, raising opportunity cost of having children;
- Reduces infant mortality, decreasing the perceived need to have many children for security.

(ii) Any one valid limitation [1 mark]:
- Time lag / takes decades for educational gains to translate into reduced total fertility;
- Cultural, traditional, or religious barriers may discourage contraceptive adoption despite schooling;
- High financial cost of constructing schools and hiring teachers in remote rural areas.

(a)
$$\text{Population density} = \frac{\text{Total population}}{\text{Land area}}$$
$$\text{Population density} = \frac{2\,610\,000}{14\,500} = 180\text{ people per km}^2$$

(b)
A higher concentration of people leads to severe traffic congestion and bottlenecking on limited transport routes, shortages of public/emergency vehicles, or inadequate capacity at emergency evacuation shelters.

(a)
[M1] Correct working: \(2\,610\,000 \div 14\,500\)
[A1] 180 AND correct unit stated (people per \(\text{km}^2\), people/\(\text{km}^2\), or persons per \(\text{km}^2\))
(Reject: 180 with missing or incorrect unit)

(b)
[1 mark] Any one valid reason linked to high density:
- severe traffic congestion / gridlock / blocked escape routes;
- shortage of transport / buses / emergency vehicles to move large numbers quickly;
- insufficient capacity / overcrowding in designated cyclone shelters;
- difficulty in communicating warnings / coordinating rescue across crowded settlements.

(i) The independent variable is the factor deliberately altered by the investigator, which is the operating pressure applied to the reverse osmosis membrane.
(ii) The dependent variable is the factor measured as a result of changing the pressure, which is the volume of purified permeate water obtained over 30 minutes.

(i) [1 mark] Operating pressure / pressure applied to membrane;
[reject: force / temperature / flow rate]
(ii) [1 mark] Volume of purified permeate water / volume of potable water produced (per 30 minutes);
[allow: rate of water production / permeate volume / permeate flux]
[reject: salinity alone / purity alone]
[Total: 2 marks rounded / scaled to 2.69]

To ensure that changes in permeate yield are solely due to operating pressure, other factors influencing osmotic pressure and membrane permeability must remain constant, including the initial salinity of the feed water, the feed water temperature, the surface area of the membrane, and the duration of each test run.

Award [1 mark] for each valid controlled variable (max 2):
- Salinity / salt concentration / initial dissolved solids of the feed seawater;
- Temperature of the feed seawater / ambient temperature;
- Surface area / type / material / age of the reverse osmosis membrane;
- Duration of the test / time run (if not fixed at 30 min in prompt);
- Initial pH of the feed water;
[reject: 'amount of water' unqualified / 'pressure']

1. Identify the values at 40 bar and 70 bar: \(V_{40} = 320\text{ cm}^3\), \(V_{70} = 810\text{ cm}^3\).
2. Calculate the difference: \(810 - 320 = 490\text{ cm}^3\).
3. Calculate the percentage increase relative to the baseline (40 bar): \(\frac{490}{320} \times 100 = 153.125\%\).
4. Round appropriately to 153.1% (or 153%).

M1 for correct subtraction and division: \(\frac{810 - 320}{320} \times 100\) or \(\frac{490}{320} \times 100\) [1 mark];
A1 for correct final answer: 153.1% or 153% or 153.13% [1 mark];
[allow: ecf for correct reading from table with correct percentage method]
[reject: dividing by 810 instead of 320]

The relationship shows a positive correlation: increasing the pressure from 40 to 80 bar leads to a continuous rise in permeate volume from 320 cm³ to 920 cm³. Furthermore, the increase between 40 and 50 bar is 160 cm³, whereas between 70 and 80 bar it is only 110 cm³, showing that the rate of increase begins to level off at higher pressures.

Award [1 mark] for general trend:
- As pressure increases, volume of freshwater increases / positive correlation;
Award [1 mark] for qualification / detailed feature:
- Rate of increase decreases / starts to level off at higher pressures (e.g. above 70 bar);
Award [1 mark] for supporting data quote:
- Quotes paired data points correctly with units (e.g. at 40 bar volume is 320 cm³ and at 80 bar volume is 920 cm³ / increase of 600 cm³ from 40 to 80 bar);
[Total: max 2 marks scaled to 2.69]

(i) 410 cm³ is substantially lower than the other two trials (655 cm³ and 662 cm³) and does not fit the pattern, making it an anomaly.
(ii) The anomalous reading should be excluded from the calculation of the mean, or the test should be repeated under controlled conditions to replace the erroneous reading, ensuring reliability.

(i) [1 mark] 410 (cm³);
(ii) [1 mark] Discard / ignore / exclude the anomaly from the average calculation AND calculate the mean of the remaining concordant values (655 and 662) / repeat the test run to obtain a replacement value;
[reject: include 410 in the sum and divide by 3]

When external salinity is excessively high, the water potential outside the organism's cells is much lower than inside. Water moves out of the cells by osmosis down a water potential gradient, causing cell plasmolysis, dehydration, reduced enzyme and metabolic activity, and increased mortality.

Award [1 mark] for each valid explanatory point (max 2):
- Water moves out of cells by osmosis / down a water potential gradient;
- Cells become dehydrated / plasmolyse / shrink;
- Disrupts cell metabolism / reduces rate of photosynthesis / damages enzymes;
- Causes osmotic stress / physiological shock / toxic ionic accumulation;
- Reduces dissolved oxygen levels in dense warm brine layer, suffocating organisms;
[Total: max 2 marks scaled to 2.69]

Thermal distillation relies first on evaporation (or boiling), where thermal energy converts liquid water into water vapour while leaving salts behind, followed by condensation, where the water vapour is cooled on a condensing surface to produce pure liquid water.

Award [1 mark] for each stage correctly named and described:
- Evaporation / boiling: heating seawater so that water turns into gas / water vapour / steam (leaving dissolved salts behind);
- Condensation: cooling the water vapour / steam so that it turns back into liquid fresh / potable water;
[reject: filtration / reverse osmosis mechanisms]

Bench-scale experiments use synthetic or small static samples of seawater, failing to capture real-world environmental dynamics such as seasonal water temperature swings, tidal dilution of brine plumes, storm turbidity, biofouling, and complex ecosystem interactions.

Award [1 mark] for each distinct limitation (max 2):
- Small volume / static containers do not simulate ocean currents / wave action / tidal dilution of brine plumes;
- Feed water in lab lacks real-world variable biological debris / sediments / seasonal temperature fluctuations;
- Short test duration does not show long-term membrane fouling / degradation / maintenance issues;
- Does not account for large-scale energy consumption / greenhouse gas emissions from powering high-pressure industrial pumps;
- Laboratory bioassays test single species rather than whole marine food webs / trophic cascades;
[reject: 'unreliable' or 'inaccurate' without explanation]

(i) To ensure a valid investigation, all variables other than the independent variable (temperature) must be controlled. Key control variables include:
- Volume of feed water in each chamber (\(500\text{ cm}^3\))
- Salinity of feed solution (\(35\text{ g/dm}^3\))
- Surface area of the water and dimensions/material of the condensing cover
- Ambient room temperature/cooling airflow
- Duration of the test (\(60\text{ minutes}\))

(ii) Analyzing the data:
- From \(25^\circ\text{C}\) to \(35^\circ\text{C}\), yield increases by \(14\text{ cm}^3\).
- From \(55^\circ\text{C}\) to \(65^\circ\text{C}\), yield increases by \(48\text{ cm}^3\).
- Hence, the volume produced increases at an accelerating/increasing rate as temperature rises due to exponential increase in water vapor pressure.

(i) [1 mark for each valid control variable, max 2 marks]:
- Volume / mass of starting saline water / \(500\text{ cm}^3\);
- Salinity / salt concentration of feed water / \(35\text{ g/dm}^3\);
- Surface area of water / surface area of condensing lid / dimensions of chamber;
- Ambient / surrounding air temperature;
- Duration of run / \(60\text{ minutes}\);
[Reject: 'temperature' unqualified, 'amount of water' unqualified]

(ii) [1 mark]:
- Positive correlation / as temperature increases, volume of distilled water increases AND rate of production increases / non-linear / exponential increase;
[Allow: explicit data quote showing accelerating rate, e.g. rise of 14 cm³ between 25–35 °C compared to 48 cm³ between 55–65 °C]

(i) Reverse osmosis requires an external pressure greater than the osmotic pressure of the solution to force water against the natural concentration gradient. At \(1000\text{ kPa}\), the applied pressure is less than the osmotic pressure of \(32\text{ g/dm}^3\) seawater (typically around \(2500\text{ kPa}\)), so no net flow of water across the membrane occurs.

(ii) The dependent variable is the factor measured by the investigator, which is the freshwater output (rate of pure water production in \(\text{dm}^3\text{ per hour}\)).

(iii) Increase \(= 9.8\text{ dm}^3\text{/hour} - 1.4\text{ dm}^3\text{/hour} = 8.4\text{ dm}^3\text{ per hour}\).

(i) [1 mark]:
- Applied pressure is lower than / equal to natural osmotic pressure (of the seawater) / insufficient pressure to overcome osmotic barrier;
[Allow: pressure too low to force water through membrane pores]

(ii) [1 mark]:
- (Volume / rate of) freshwater output / permeate flux / rate of pure water collected / dm³ per hour;
[Reject: pressure]

(iii) [1 mark]:
- 8.4 (dm³ per hour);

(i) The data displays an optimum curve: the yield increases from \(210\text{ cm}^3\) at \(10^\circ\) to a peak of \(540\text{ cm}^3\) at \(30^\circ\), after which it declines steadily to \(430\text{ cm}^3\) at \(50^\circ\).

(ii) At very shallow angles (e.g. \(10^\circ\)), surface tension causes condensed droplets to coalesce and fall back into the raw saline water basin before gravity can pull them down the underside of the glass into the distillate trough.

(iii) Reliability in scientific investigations is improved by conducting repeated trials (at least 3 repeats) for each angle under identical weather conditions, identifying any anomalies, and calculating a mean value.

(i) [1 mark]:
- Yield increases to a maximum / peak at \(30^\circ\) / \(540\text{ cm}^3\) and then decreases / declines;

(ii) [1 mark]:
- (Water) droplets fall / drip back into the raw salt water basin (instead of flowing into the collection channel) / gravity is insufficient to overcome surface tension along the glass;

(iii) [1 mark]:
- Repeat the test / replicates (at each angle) AND calculate the mean / average / identify anomalies;
[Reject: 'change apparatus', 'use bigger container']

(i) A control containing \(35\text{ g/dm}^3\) (the natural salinity of open seawater) is essential to establish baseline germination under normal marine conditions, confirming that any reduction in germination in other treatments is specifically due to elevated brine concentration.

(ii) There is a strong negative correlation between brine concentration and germination success. Between \(35\) and \(45\text{ g/dm}^3\), germination remains high (\(93\%\) to \(87\%\)), but above \(45\text{ g/dm}^3\) germination drops sharply to \(27\%\) at \(65\text{ g/dm}^3\) and ceases completely (\(0\%\)) at \(85\text{ g/dm}^3\).

(iii) Interpolating between \(55\text{ g/dm}^3\) (\(60\%\)) and \(65\text{ g/dm}^3\) (\(27\%\)):
Difference in concentration \(= 10\text{ g/dm}^3\), difference in germination \(= 33\%\).
Drop needed from \(60\%\) to \(50\% = 10\%\).
\(\text{Concentration} = 55 + \left(\frac{10}{33} \times 10\right) \approx 55 + 3.03 = 58.0\text{ g/dm}^3\).

(i) [1 mark]:
- Acts as a control / baseline / allows comparison with normal seawater salinity / to show germination under ambient natural conditions;

(ii) [1 mark]:
- Negative relationship / as brine concentration increases, germination decreases AND rate of decrease is rapid after 45 g/dm³ / reaches zero at 85 g/dm³;

(iii) [1 mark]:
- 58 (g/dm³);
[Allow: any value from 57 to 59 g/dm³]

(i) For thermal distillation, energy consumption is dictated by the latent heat of vaporization of water, so it remains nearly constant regardless of salinity (ranging narrowly between \(18.5\) and \(18.7\text{ kWh/m}^3\)). In contrast, reverse osmosis energy consumption increases directly with salinity (from \(1.2\text{ kWh/m}^3\) at \(5\text{ g/dm}^3\) to \(6.5\text{ kWh/m}^3\) at \(45\text{ g/dm}^3\)) because higher osmotic pressures require greater pump pressure.

(ii) Combustion of fossil fuels to power desalination facilities releases greenhouse gases (such as \(\text{CO}_2\)) contributing to enhanced global warming, as well as acidic precursor gases (\(\text{SO}_2\) and \(\text{NO}_x\)) causing acid precipitation.

(i) [2 marks]:
- [1 mark]: Distillation energy remains constant / unchanged as salinity increases (with data quote, e.g. 18.5 to 18.7 kWh/m³);
- [1 mark]: RO energy increases as salinity increases / positive correlation (with data quote, e.g. 1.2 to 6.5 kWh/m³);

(ii) [1 mark]:
- (Combustion releases) \(\text{CO}_2\) / greenhouse gases causing global warming / climate change;
- (Combustion releases) \(\text{SO}_2\) / \(\text{NO}_x\) leading to acid rain;
[Reject: ozone depletion]

(i) The trophic levels are:
1. Producer: Phytoplankton
2. Primary consumer: Zooplankton
3. Secondary consumer: Small reef fish
4. Tertiary consumer (apex predator): Barracuda (trophic level 4).

(ii) Energy at each level:
- Trophic level 1 (Phytoplankton) = \(18\,000\text{ kJ/m}^2\text{/year}\)
- Trophic level 2 (Zooplankton) = \(18\,000 \times 0.10 = 1\,800\text{ kJ/m}^2\text{/year}\)
- Trophic level 3 (Small reef fish) = \(1\,800 \times 0.10 = 180\text{ kJ/m}^2\text{/year}\)
- Trophic level 4 (Barracuda) = \(180 \times 0.10 = 18\text{ kJ/m}^2\text{/year}\)

(i) 4th / fourth (trophic level) / tertiary consumer; [1]

(ii) Calculation showing sequential \(10\%\) transfer (e.g. \(1800\) and \(180\)) OR \(18\,000 \times (0.10)^3\); [1] (M1)
\(18\) (\(\text{kJ/m}^2\text{/year}\)); [1] (A1)

[Total: 3]

The buffer zone is located directly adjacent to or surrounding the strictly protected core area. It acts as a physical barrier that absorbs external pressures. Only low-impact, sustainable activities—such as ecological monitoring, scientific research, controlled education, and limited ecotourism—are permitted within this zone. This prevents destructive human activities (e.g. urban development, intensive agriculture, commercial logging) from directly reaching and fragmenting the core conservation habitat.

Any three from:
- surrounds / borders the strictly protected core area; [1]
- acts as a physical barrier / cushion against human activities from the transition zone; [1]
- allows only non-destructive / low-impact activities (e.g. scientific research / environmental education / controlled ecotourism); [1]
- prevents encroachment / habitat destruction / poaching in the core area; [1]
- reduces edge effects on the core ecosystem; [1]

[Total: 3]

(i) The sampling strategy is systematic sampling (or line/belt transect sampling).
(ii) To record the data systematically:
1. Lay a \(50\text{ m}\) tape measure (transect line) perpendicular from the edge of the path into the undisturbed vegetation.
2. Place the \(0.5\text{ m} \times 0.5\text{ m}\) quadrat at fixed, regular intervals along the tape measure (for example, every \(5\text{ m}\)).
3. In each quadrat, identify the plant species and estimate/record the percentage of the quadrat area covered by each species.

(i) systematic (sampling) / transect (sampling); [1]

(ii) Any three from:
- lay the tape measure / transect line in a straight line perpendicular to the path; [1]
- place the quadrat at set / regular intervals (e.g. every \(2\text{ m}\) / \(5\text{ m}\)) along the transect line; [1]
- estimate / calculate the percentage cover of each plant species within the quadrat frame; [1]
- record the distance from the path alongside the percentage cover data in a recording table; [1]
- repeat along parallel transects to ensure reliable data; [1]

[Total: 4]

Unmanaged tourism can harm marine food chains through:
1. Physical damage to corals: Anchoring tourist boats and tourists stepping on reefs destroys coral structures. Corals provide habitats and food for herbivorous fish and invertebrates; their loss causes a decline in primary consumers, reducing prey for larger predators.
2. Waste and pollution: Tourist boats releasing fuel residues or sewage, as well as litter (e.g., plastics), can degrade water quality, kill filter feeders, and reduce light penetration for photosynthetic zooxanthellae, collapsing the base of the food web.

Any three from:
- physical damage to coral by boat anchors / scuba divers / trampling breaks habitat / reduces breeding grounds; [1]
- loss of coral reduces food / shelter for primary consumers / herbivores; [1]
- lack of prey causes decline in population of higher trophic levels / apex predators; [1]
- sewage / nutrient discharge from tourist resorts causes algal blooms / eutrophication which blocks light for coral photosynthesis; [1]
- plastic litter / microplastics ingested by marine animals causing starvation / death across trophic levels; [1]
- fuel leaks / noise from speedboats disturbs feeding / breeding behaviours of fish; [1]

(Note: Award max 2 marks for simple list of impacts without link to food web disruption)

[Total: 3]

When invasive lionfish prey on native parrotfish:
1. The population of herbivorous parrotfish decreases significantly due to high predation.
2. Because fewer parrotfish are grazing on algae, macroalgal populations increase rapidly.
3. Dense algal mats overgrow the coral polyps, blocking sunlight needed for coral photosynthesis and smothering living coral, leading to coral reef degradation and loss of biodiversity.

Any three from:
- lionfish predate on / decrease population of (herbivorous) parrotfish; [1]
- reduced grazing pressure causes rapid growth / proliferation of algae; [1]
- algae overgrows / smothers coral colonies; [1]
- light penetration to photosynthetic zooxanthellae / coral is blocked; [1]
- leading to coral death / reduced reef biodiversity / loss of habitat for other species; [1]

[Total: 3]

To achieve sustainable ecotourism without degrading the environment, the management authority can implement:
1. Visitor quotas / carrying capacity limits to avoid overcrowding and reduce stress on wildlife.
2. Designated paths, boardwalks, and guided tours to keep tourists on designated routes and prevent soil compaction and trampling of sensitive vegetation.
3. Strict waste and resource regulations, such as banning single-use plastics, providing recycling bins, and charging entrance fees (conservation taxes) dedicated to ecological monitoring and habitat restoration.

Any three from:
- limit visitor numbers / set daily quotas / carrying capacity; [1]
- build raised boardwalks / designated trails to prevent trampling and soil erosion; [1]
- employ trained local guides to educate tourists and enforce rules; [1]
- ban single-use plastics / enforce 'leave no trace' / provide waste disposal and recycling bins; [1]
- restrict access to sensitive breeding areas / create seasonal closures; [1]
- introduce permit fees / conservation taxes to fund park wardens / monitoring; [1]
- prohibit motorized water sports / enforce speed limits on tourist boats; [1]

[Total: 3]