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

Decrease in forest cover = \(450\,000 - 315\,000 = 135\,000\text{ ha}\).
Percentage decrease = \(\frac{135\,000}{450\,000} \times 100\% = 30.0\%\).

1 mark for correct method: \(\frac{450\,000 - 315\,000}{450\,000} \times 100\) or \(\frac{135\,000}{450\,000} \times 100\);
0.5 mark for correct value: 30 / 30.0 (%);

Adaptation means adjusting behaviour, infrastructure, or systems to cope with the unavoidable impacts of climate change. A coastal strategy includes installing hard engineering flood defences like sea walls or raising building foundations.

1 mark for definition: actions / adjustments to reduce vulnerability / cope with the impacts / effects of climate change;
0.5 mark for coastal example: building sea walls / groynes / tidal barriers / flood embankments / building legislation near coasts / raising buildings on stilts;
Guidance: ignore mitigation strategies such as reforestation or renewable energy.

A floating boom encloses the spill on the surface to contain the oil and stop it from reaching vulnerable shorelines. In rough seas, strong wave action causes oil to splash over the boom or get swept underneath.

1 mark for function: contains / encloses the oil / prevents oil spreading (towards coastlines/ecosystems) / concentrates oil for skimmers;
0.5 mark for reason: high waves / rough waters cause oil to wash over (splashover) / pass underneath the boom / boom breaks / tears in turbulent seas;

(a) Shale is a fine-grained sedimentary rock with very small, unconnected pores, making it impermeable to water.
(b) Marble is formed when limestone undergoes intense heat and pressure, so it belongs to the metamorphic group.

(a) 1 mark for impermeable;
(b) 0.5 mark for metamorphic;

(a) The screening stage captures large floating and suspended debris before further treatment.
(b) Chlorination is the chemical disinfection process that kills disease-causing microorganisms such as bacteria and viruses to make water safe for human consumption.

(a) 0.5 mark for screening / screens;
(b) 1 mark for kill bacteria / pathogens / microorganisms / microbes / sterilise / disinfect;
Guidance: reject 'clean the water' or 'filter impurities' without reference to killing microorganisms.

1. Calculate the change in forest area: \(480\text{ km}^2 - 372\text{ km}^2 = 108\text{ km}^2\). 2. Calculate the percentage decrease: \(\frac{108}{480} \times 100 = 22.5\%\).

Correct subtraction showing loss of 108 [0.5]; Correct calculation method: \(\frac{108}{480} \times 100\) [0.5]; Correct final answer: 22.5 (%) [0.5]. Allow [1.5] for correct final answer with no working shown. (ecf from incorrect subtraction).

1. Use the energy efficiency formula: \(\text{Efficiency} = \frac{\text{Energy in primary consumers}}{\text{Energy in primary producers}} \times 100\). 2. Substitute the values: \(\frac{9\ 240}{84\ 000} \times 100 = 11.0\%\).

Correct working shown: \(\frac{9\ 240}{84\ 000} \times 100\) [1]; Correct answer: 11 / 11.0 (%) [0.5]. Allow full credit [1.5] for correct answer without working.

1. Use the formula: \(\text{Population density} = \frac{\text{Total population}}{\text{Land area}}\). 2. Substitute the values: \(\frac{147\ 200}{3\ 200} = 46\text{ people per km}^2\).

Correct working shown: \(\frac{147\ 200}{3\ 200}\) [1]; Correct value: 46 (people per \(\text{km}^2\)) [0.5]. Allow full credit [1.5] for correct answer without working.

When forests are cleared from hillsides, fewer raindrops are intercepted by tree canopies and less water is absorbed by tree roots. This increases the speed and volume of surface run-off entering river channels. Without tree roots binding the soil, topsoil is eroded and washed into the river (silting/sedimentation), which raises the river bed and lowers the channel capacity to hold water, resulting in overflow and downstream flooding.

Award marks for any valid linked points [max 2.5 marks]:
- (Lack of canopy leads to) reduced interception / less water absorbed/transpired by tree roots [1 mark];
- Increased surface run-off / water reaches the river channel much faster [1 mark];
- Soil erosion occurs / topsoil is washed into the river because roots no longer bind soil [1 mark];
- Siltation / sediment deposition raises the riverbed / decreases channel cross-sectional area/holding capacity [1 mark];
- River overflows banks more easily during heavy rain [0.5 mark].

Note: Accept ORA for forested slopes. Maximum 2.5 marks total.

Inorganic fertilisers containing nitrates and phosphates wash into the lake, causing rapid growth of algae on the surface (algal bloom). This layer blocks sunlight, preventing underwater plants from photosynthesising and causing them to die. When the algae and plants die, aerobic decomposers (bacteria) break down the organic matter and consume large volumes of dissolved oxygen for respiration. The resulting anoxic (low oxygen) conditions suffocate fish and other aquatic organisms.

Award marks for any valid linked points [max 2.5 marks]:
- Run-off of nitrates/phosphates causes rapid algal growth / algal bloom [1 mark];
- Sunlight is blocked, preventing photosynthesis of submerged vegetation / submerged aquatic plants die [1 mark];
- Bacteria / decomposers break down dead plant/algal matter [1 mark];
- Bacteria multiply and use up dissolved oxygen during (aerobic) respiration [1 mark];
- Water becomes deoxygenated / anoxic, so fish cannot respire and die [0.5 mark].

Note: Do NOT credit statements claiming algae consume all the oxygen during life. Maximum 2.5 marks total.

To plot the line graph correctly:
1. Axes and Labels: Place 'Year' on the horizontal (x) axis with years 2018 to 2022 evenly spaced. Place 'Forest area cleared / thousand hectares' (or 'Forest area cleared / $10^3$ ha') on the vertical (y) axis.
2. Scale: Select a sensible linear scale on the y-axis starting at 0 up to 250 (e.g. increments of 50 thousand hectares per major grid division) so the data occupies more than 50% of the available vertical grid space.
3. Plotting and Lines: Plot each coordinate accurately using neat crosses (x) or encircled dots ($\odot$):
- $(2018, 40)$
- $(2019, 75)$
- $(2020, 130)$
- $(2021, 180)$
- $(2022, 220)$
4. Join consecutive points with a sharp pencil and straight, ruled lines.

Award 1 mark for each of the following criteria:
- Both axes labelled correctly with quantity and unit: x-axis as 'Year' AND y-axis as 'Forest area cleared / thousand hectares' (or 'Forest area cleared / $10^3$ ha');
- Sensible linear scale chosen for the y-axis such that the plotted data occupies more than half of the grid in both directions;
- All five points plotted accurately to within half a small square and joined point-to-point with straight, thin ruled lines;

Guidance:
- Reject if points are joined by a thick, sketchy, or freehand line.
- Reject if the line is extrapolated before 2018 or beyond 2022.

To construct the line graph:
1. Axes and Labels: Place the independent variable, 'Distance downstream / m', on the horizontal (x) axis. Place the dependent variable, 'Dissolved oxygen concentration / mg/dm$^3$' (or $\text{mg dm}^{-3}$), on the vertical (y) axis.
2. Scales: Choose uniform, linear scales for both axes:
- x-axis: 0 to 250 m with regular increments (e.g. 50 m per major interval).
- y-axis: 0 to 10.0 $\text{mg/dm}^3$ (e.g. 1.0 or 2.0 $\text{mg/dm}^3$ per major interval).
Ensure the graph fills more than half the grid.
3. Plotting: Accurately plot all 6 points using small crosses or encircled dots:
- $(0, 9.0)$
- $(50, 2.5)$
- $(100, 1.5)$
- $(150, 3.0)$
- $(200, 6.0)$
- $(250, 8.5)$
4. Line: Connect adjacent plotted points cleanly with a ruler.

Award 1 mark for each of the following criteria:
- Both axes fully labelled with quantity and correct units: 'Distance downstream / m' (x-axis) and 'Dissolved oxygen concentration / mg/dm$^3$' or 'mg dm$^{-3}$' (y-axis);
- Sensible, linear scales starting at 0 on both axes that use more than 50% of the grid area;
- All six points correctly plotted to within half a small square and joined with neat, ruled straight lines;

Guidance:
- Reject non-linear or unevenly spaced scales.
- Accept continuous smooth curve connecting points if plotted with precision, but prefer point-to-point ruled lines.

1. Loss of tree canopy reduces precipitation interception, and fewer roots reduce water uptake and transpiration, leading to increased surface run-off.
2. Without root systems binding the soil and canopy protecting against raindrops, topsoil is washed away (soil erosion).
3. Eroded sediment is deposited in river channels (silting/sedimentation), raising the riverbed and reducing water-holding capacity, causing floodwaters to overflow into downstream settlements during heavy rainfall.

Any three from:
- loss of tree canopy reduces interception of precipitation;
- reduced transpiration / less water taken up by tree roots (leaves soil saturated);
- increased (rate / volume of) surface run-off / overland flow;
- lack of root binding / bare soil exposed leads to increased soil erosion / wash-off;
- soil/sediment deposited in the river / siltation / silting of riverbed;
- reduces the water-holding capacity / cross-sectional area of the river channel;
- river overflows its banks more quickly / flood peak arrives faster;
[Max 3 marks]
[Guidance: Accept ORA for forested areas. Do not credit simply 'trees hold water' without mechanism.]

1. Climate change causes higher average temperatures, changing weather patterns, and longer, more frequent droughts.
2. Drought-resistant crops require less water and can tolerate dry soil conditions, maintaining food production/yields and protecting farmers' incomes and food security.

Any two linked points from:
- climate change causes more frequent / severe droughts / unpredictable rainfall patterns;
- crops can grow / survive / produce yields with lower soil moisture / less water / under water stress;
- maintains food security / prevents famine / crop failure;
- maintains farm income / livelihoods during prolonged dry periods;
[Max 2 marks]

1. Wild relatives contain diverse alleles and genetic traits that may have been bred out of commercial monoculture crops.
2. If commercial crops are threatened by new pests, diseases, or environmental changes, genes from wild varieties stored in seed banks can be bred into crops to ensure resilience and food supplies.

Any two from:
- preserves genetic diversity / gene pool / prevents genetic depletion / extinction of rare varieties;
- wild relatives contain genes for pest resistance / disease resistance / drought tolerance / salinity tolerance;
- genes can be used in plant breeding / genetic engineering / crop improvement;
- allows adaptation to new environmental challenges / emerging diseases / climate change;
[Max 2 marks]
[Guidance: Reject 'stores food for emergency eating'.]

1. Large areas of vegetation and topsoil are cleared, and overburden (waste rock) is piled up.
2. Rain falls on exposed rock and waste piles, washing loose sediment into streams, increasing turbidity and reducing light penetration.
3. Water reacts with exposed sulfur-bearing rocks or heavy metals, creating acidic runoff (acid mine drainage) or dissolving toxic ions, which enter watercourses and harm aquatic life.

Any three from:
- clearance of vegetation / large piles of loose overburden / waste rock exposed to rain;
- surface run-off washes sediment / silt into streams, causing turbidity / blocking light / smothering fish gills;
- exposure of rocks containing sulfur / sulfides reacts with water and air to form acid (mine drainage);
- acidic water / runoff dissolves and leaches toxic heavy metals (e.g. lead, cadmium, arsenic) into streams;
- lowers the pH of the water, killing aquatic organisms / disrupting food chains;
[Max 3 marks]

1. Crude oil floats on the water surface where seabirds land and feed.
2. The oil coats their feathers, matting them together, which destroys the trapped air layer that provides thermal insulation and buoyancy, leading to hypothermia and drowning.
3. Birds try to clean their plumage by preening, ingesting toxic oil, which damages their liver, kidneys, digestive tract, and reproductive systems.

Any three from:
- oil coats / clogs feathers / plumage;
- destroys natural waterproofing / breaks down water repellency;
- loss of buoyancy causes birds to become heavy and drown;
- loss of thermal insulation leading to hypothermia / freezing to death;
- birds ingest toxic oil when preening / cleaning feathers;
- poisoning / toxic damage to internal organs (liver / kidneys / digestive tract);
- reduces ability to fly / hunt / feed, leading to starvation;
[Max 3 marks]

1. Staying in school and pursuing careers leads to delayed marriage and older age at first childbirth, reducing the total reproductive lifespan.
2. Educated women gain greater knowledge and autonomy regarding reproductive health and family planning, leading to more consistent use of contraception and smaller desired family sizes.

Any two from:
- women stay in education longer, leading to delayed marriage / older age at first child / shorter reproductive window;
- greater career / employment opportunities provide financial independence, reducing desire for large families;
- increased knowledge / awareness / understanding of contraception / family planning methods;
- greater empowerment / autonomy to make decisions regarding family size / birth spacing;
[Max 2 marks]

1. Geothermal energy relies on hot rocks and magma relatively close to the Earth's crust to heat water into steam for turbines.
2. These geological conditions are geographically restricted primarily to active plate boundaries and volcanic hotspots; in geologically stable areas, crustal rock temperatures near the surface are too low, and drilling deep enough is prohibitively expensive.

Any two from:
- high geothermal heat / magma / hot rocks close to the surface are geographically restricted;
- mostly located near tectonic plate boundaries / volcanic areas / hotspots;
- many countries are situated on stable continental crust / far from plate boundaries where underground temperatures near the surface are low;
- deep drilling in non-volcanic regions is technically difficult / economically unviable / too expensive;
[Max 2 marks]

1. Purpose: Chlorine is added to kill pathogenic bacteria, viruses, and parasites to make water safe to drink (potable).
2. Control: If the dose is too low, dangerous pathogens survive and waterborne diseases (like cholera) spread; if the dose is too high, it gives water an unpleasant taste/smell, irritates consumers, and can react with organic compounds to form harmful chemical by-products.

Purpose (1 mark):
- to disinfect / sterilise water / kill bacteria / pathogens / microorganisms (e.g. cholera bacteria);
Control (1 mark):
- if concentration is too low, pathogens / bacteria survive / water is unsafe;
OR
- if concentration is too high, water tastes / smells unpleasant / forms harmful / toxic chemical by-products / irritates skin and eyes;
[Max 2 marks]

1. Canopy loss and reduced interception: Without tree foliage, rainwater reaches the soil surface directly rather than being intercepted and evaporated.
2. Increased surface run-off: Soil quickly becomes saturated or compacted, reducing water infiltration and increasing rapid surface run-off into drainage basins.
3. Sedimentation / Silting: Unprotected topsoil is washed into rivers by surface run-off, accumulating on the river bed, which reduces the channel's cross-sectional area and holding capacity, leading to water overflowing the banks.

Award marks for linked explanatory points (max 2.5 marks):
- Reduced interception by tree leaves / canopy [1];
- Less infiltration / higher rate / volume of surface run-off (into streams/rivers) [1];
- Soil erosion leads to silt / sediment entering river channels, reducing river capacity / raising the river bed [1].
[Guidance: Accept alternative valid linked mechanisms such as loss of root uptake reducing soil water storage capacity.]

1. Leaching / Run-off: Heavy rain washes soluble nitrate ions from the soil into surrounding freshwater bodies.
2. Algal bloom: High nutrient concentrations stimulate rapid multiplication of algae at the water surface, blocking sunlight from reaching deeper aquatic vegetation.
3. Deoxygenation: Submerged plants and algae die; aerobic decomposers (bacteria) break down the organic matter and consume dissolved oxygen in respiration, lowering dissolved oxygen levels to the point where fish cannot survive.

Award marks for linked explanatory points (max 2.5 marks):
- Leaching / surface run-off carries nitrates / nutrients into the lake, causing rapid algal growth / algal bloom [1];
- Algae blocks light, causing underwater aquatic plants to die (due to lack of photosynthesis) [1];
- Aerobic bacteria / decomposers break down dead plant / algal tissue and consume dissolved oxygen (through respiration), causing fish to suffocate / die [1].
[Guidance: Award maximum marks for a clear sequential explanation of eutrophication.]

Deforestation removes the protective tree canopy and root network that binds the soil. Rainfall hits bare soil directly, dislodging particles and increasing surface run-off. This surface water carries eroded topsoil into adjacent river systems, where the particles settle out of suspension (deposition), accumulating on the river bed and causing siltation.

Award marks for any three linked points (max 1.5 marks, 0.5 per point):
- loss of vegetation canopy / roots means soil is no longer bound / protected from rainfall;
- increased surface run-off / soil is eroded / washed away;
- loose sediment / soil particles are transported into rivers and settle / deposit on the river bed / reduce channel capacity;

Guidance: Accept ORA if described in terms of intact forest. Ignore generic references to 'pollution' without sediment.

Adaptation refers to changing strategies, infrastructure, or behaviours to survive and reduce vulnerability to the current and future impacts of climate change (as opposed to mitigation, which aims to reduce emissions). In agriculture, this includes developing and planting genetically modified or selectively adapted drought-tolerant, flood-tolerant, or salt-resistant crop varieties, or installing efficient drip irrigation.

1 mark for definition; 0.5 mark for valid agricultural example (total 1.5 marks):
- definition: actions / adjustments taken to reduce vulnerability / cope with / live with the effects of climate change (1);
- example: planting drought-resistant / flood-tolerant / saline-resistant crops / altering sowing and harvesting dates / installing drip irrigation / rainwater harvesting for irrigation (0.5);

Guidance: Do NOT accept mitigation strategies (e.g. reducing fertiliser use to lower emissions, switching to biofuels).

Wildlife corridors are continuous strips of natural habitat linking isolated reserves or forest fragments. They allow individuals to safely move, feed, and disperse between patches without crossing human-disturbed landscapes. This movement enables gene flow and interbreeding between previously separated populations, maintaining genetic diversity and preventing local extinction.

Award marks for linked explanatory points (max 1.5 marks, 0.5 per point):
- links / joins isolated habitat fragments / nature reserves;
- allows movement / migration / dispersal of animals to find food / mates / new territory safely;
- maintains gene flow / prevents inbreeding / preserves genetic diversity / reduces local extinction risk;

Guidance: Accept references to plant seed dispersal by animals across corridors.

Bioleaching is a biological extraction method where specific bacteria (or fungi) break down low-grade ores and rocks to produce a leachate solution containing dissolved metal ions. It avoids large-scale land excavation and open pits, requiring less heavy machinery and generating fewer greenhouse gas and sulfur dioxide emissions than conventional smelting.

1 mark for description of bioleaching; 0.5 mark for valid environmental advantage (total 1.5 marks):
- description: use of bacteria / microorganisms / biological agents to extract / dissolve metals from (low-grade) ores (1);
- advantage: less habitat loss / less surface land destruction / no sulfur dioxide emissions / lower energy / fuel requirement compared to smelting / enables metal recovery from waste heaps / tailings without new excavation (0.5);

Guidance: Reject 'produces zero toxic waste' as acid drainage can still occur.

Crude oil sticks to bird feathers and clogs their structure. This strips away natural waterproofing and traps water against the skin, causing severe loss of body heat (hypothermia) and loss of buoyancy, causing birds to sink and drown. Additionally, when seabirds attempt to clean (preen) their oiled plumage, they swallow toxic hydrocarbons, leading to internal poisoning and organ failure.

Award marks for linked explanatory points (max 1.5 marks, 0.5 per point):
- oil coats / clogs feathers, disrupting interlocking barbules / natural waterproofing;
- loss of thermal insulation leading to hypothermia / loss of buoyancy causing bird to sink / drown / inability to fly to hunt for food;
- ingestion of toxic oil / hydrocarbons during preening causes internal poisoning / damage to organs / liver / kidneys;

Guidance: Mention of hypothermia or poisoning must be linked to the physical effect of the oil.

Push factors are negative social, environmental, or economic conditions in the countryside that compel people to leave (e.g. soil degradation, drought, lack of basic services, agricultural unemployment). Pull factors are positive opportunities or perceived benefits in cities that attract migrants (e.g. well-paying jobs, superior educational institutions, advanced medical facilities).

0.5 mark for correct distinction; 0.5 mark for valid push example; 0.5 mark for valid pull example (total 1.5 marks):
- distinction: push factors are negative conditions forcing people to leave an area, whereas pull factors are positive attractions drawing people into a new location (0.5);
- push example: drought / crop failure / low rural income / lack of schooling / lack of medical facilities / landlessness (0.5);
- pull example: employment opportunities / higher wages / better access to electricity and water / better hospitals / universities (0.5);

Guidance: Examples must clearly correspond to rural origins (push) and urban destinations (pull).

In a geothermal power plant, thermal energy from underground magma or radioactive decay heats water trapped in permeable rock strata. High-pressure steam (or superheated water flashed to steam) is brought to the surface through production boreholes. The expanding steam turns the blades of a turbine, which spins a generator to produce electricity.

Award marks for linked sequential points (max 1.5 marks, 0.5 per point):
- heat from subterranean hot rocks / magma heats water to produce high-pressure steam (or natural underground steam is tapped);
- high-pressure steam turns / spins a turbine;
- the turbine drives / rotates a generator which produces electricity;

Guidance: Reject answers stating that fossil fuels or uranium are burned to create steam.

Conventional water treatment for potable supply involves four sequential steps: (1) Screening to remove large debris such as sticks and plastic; (2) Sedimentation (settling) to allow suspended solids and floc to settle at the bottom; (3) Filtration through sand and gravel beds to trap fine suspended particles; and (4) Chlorination (disinfection) to kill pathogenic bacteria and microorganisms.

Award 1.5 marks for all 4 stages named correctly; 1.0 mark for 3 stages correct; 0.5 mark for 2 stages correct:
- screening / coarse mesh;
- sedimentation / settling / clarification;
- filtration / sand filter;
- chlorination / disinfection / addition of chlorine;

Guidance: Accept reverse osmosis / distillation ONLY if specifically qualified as desalination, but for standard surface freshwater treatment accept the 4 syllabus stages listed.

Arguments supporting the statement (benefits of reforestation):
- Trees absorb carbon dioxide from the atmosphere during photosynthesis and store it as biomass (carbon sequestration).
- Reforestation provides additional environmental co-benefits, such as habitat restoration, biodiversity preservation, and reduced soil erosion.
- It can be relatively inexpensive and accessible to implement at community and national scales.

Arguments challenging the statement (limitations of reforestation and importance of reducing fossil fuel use):
- Trees require many years or decades of growth before they sequester substantial amounts of carbon dioxide.
- Forests are vulnerable to disturbances such as wildfires, disease, and drought, which can release stored carbon back into the atmosphere as carbon dioxide.
- Large-scale tree planting requires substantial land area, which can compete with agricultural land needed for global food production.
- Burning fossil fuels remains the primary driver of global greenhouse gas emissions; sinks alone cannot offset unchecked emissions.
- Reducing energy demand and transitioning to energy-efficient technologies permanently prevents emissions from entering the carbon cycle.

Conclusion:
- A balanced judgement, for example: Reforestation is a valuable complementary measure, but it cannot replace the urgent requirement to reduce fossil fuel consumption, as halting greenhouse gas emissions at the source is vital to limiting global temperature rise.

Level 3 (5–6 marks):
- A balanced, well-developed evaluation that covers arguments both supporting reforestation and highlighting the necessity of reducing fossil fuel energy demand.
- Detailed scientific reasoning applied to carbon sinks, storage stability, emissions reduction, and practical limitations.
- Formulates a coherent, justified conclusion based on the evidence presented.

Level 2 (3–4 marks):
- A developed response showing some balance, or one viewpoint developed in detail with only brief reference to the alternative.
- Demonstrates understanding of carbon dioxide removal and/or emission reduction.
- A simple conclusion may be provided but may lack full justification.

Level 1 (1–2 marks):
- Isolated, descriptive points with limited explanation or scientific linkage.
- Little or no balance shown.
- No valid conclusion.

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

A pH meter (or pH probe) is standard digital fieldwork apparatus used to record in-situ water pH directly.

pH meter / pH probe [1]

Guidance: Accept 'pH sensor'. Reject 'pH paper' / 'universal indicator paper' / 'litmus paper'.

By syllabus definition, microplastics are pieces or fragments of plastic that measure less than 5 mm.

pieces / particles of plastic with a diameter / size less than 5 mm / < 5 mm [1]

Guidance: Must state 'less than 5 mm' (or '< 5 mm').

Contour ploughing follows the contours of the hill across the slope. This creates horizontal ridges and furrows that act as dams, reducing the speed of surface run-off and allowing water to infiltrate rather than washing topsoil downslope.

ploughing across / perpendicular to the slope / along the contour lines (rather than up and down) [1];
ridges / furrows act as barriers to slow down surface run-off / trap water / reduce water velocity / encourage infiltration [1]

To carry out random sampling: lay two tape measures at right angles to create a coordinate grid, generate pairs of random numbers using a calculator or random number table, and place the quadrat at the resulting intersection points.

set up two tape measures / coordinate axes along the edges of the area [1];
use a random number generator / table / app to generate coordinate pairs [1];
place the quadrat at the intersection of each pair of coordinates [1]
(max 2 marks)

The vector responsible for transmitting the malaria-causing Plasmodium parasite is the female Anopheles mosquito.

female Anopheles (mosquito) [1]

Guidance: Accept Anopheles mosquito. Reject 'male Anopheles' or just 'mosquito' alone without Anopheles.

Mechanical containment and recovery techniques for marine oil spills include booms (floating barriers to enclose and contain oil) and skimmers (devices that skim oil off the water surface). Sorbents may also be used.

Award [1] mark for each valid method (max 2):
- (floating) booms / containment booms [1]
- skimmers / skimming devices [1]
- sorbents / absorbent barriers [1]

Guidance: Reject chemical methods such as 'dispersants' / 'detergent sprays' or 'controlled burning'.

Heat loss from buildings can be minimized by installing thermal insulation (in roofs, lofts, or cavity walls), installing double/triple-glazed windows, or fitting draught excluders.

(loft / wall / roof / cavity) insulation / double glazing / triple glazing / draught proofing [1]

According to the Cambridge 0680 syllabus, igneous rocks (granite, basalt), metamorphic rocks (marble, slate), and the sedimentary rock shale are classified as impermeable.

granite / basalt / slate / marble / shale [1]

Guidance: Reject 'limestone' or 'sandstone' (permeable rocks).

A pitfall trap is a container set flush with the soil surface into which ground-dwelling invertebrates fall and become trapped for counting and identification.

pitfall trap [1];
Ignore: pooter / sweep net / quadrat.

The stage is chlorination (or disinfection). Chlorine is added to destroy harmful microorganisms and pathogens, ensuring the water is safe to drink.

chlorination / disinfection [1];
to kill bacteria / pathogens / sterilise the water / disinfect water [1];
Reject: cleans the water / filters impurities.

Microplastics are defined as pieces or fragments of plastic that are smaller than 5 mm in diameter.

plastic pieces / fragments less than / under 5 mm (in diameter / size) [1];
Accept: \(< 5\text{ mm}\).

Terracing transforms a continuous steep slope into a series of stepped flat platforms. This cuts down the speed and volume of surface run-off and allows rainwater to infiltrate into the ground rather than washing away fertile topsoil.

Any two from:
- creates flat / stepped areas (breaking up the continuous slope) [1];
- reduces the speed / velocity of surface run-off / water flow [1];
- increases infiltration / allows more water to soak into the soil [1];
- traps sediment / prevents topsoil being washed downhill [1].

The malaria parasite (Plasmodium) is transmitted between humans by the bite of the female Anopheles mosquito.

female Anopheles (mosquito) [1];
Accept: Anopheles mosquito;
Reject: mosquito alone / male Anopheles.

Basalt (igneous) and slate (metamorphic) are impermeable rocks because they lack interconnected pore spaces through which water can flow. Limestone and sandstone are permeable sedimentary rocks.

basalt [1];
slate [1];
Note: If candidate gives more than two rocks, subtract 1 mark for each incorrect extra rock.

Floating booms are used as physical barriers to surround and contain the oil slick on the surface. Chemical dispersants or detergent sprays are applied to break the oil slick into tiny droplets that disperse through the water column.

Physical containment: (floating) boom(s) / skimmers / sorbents [1];
Chemical method: detergent sprays / chemical dispersants / dispersant sprays [1];
Accept: controlled burning under physical/thermal management if stated explicitly.

Step 1: Calculate the absolute decrease in forest area:
4 800 km2 - 3 480 km2 = 1 320 km2

Step 2: Calculate the percentage decrease:
(1 320 / 4 800) * 100 = 27.5%

Award 1 mark for correct subtraction or method: (4 800 - 3 480) / 4 800 * 100 [1]; Award 1 mark for correct final value: 27.5 (%) [1]; Allow ecf if arithmetic error in subtraction but correct percentage formula applied.

Step 1: Calculate total renewable electricity generation:
170 GWh + 119 GWh = 289 GWh

Step 2: Calculate percentage of total generation:
(289 / 850) * 100 = 34.0%

Award 1 mark for sum of renewable energy divided by total: (170 + 119) / 850 * 100 or 289 / 850 [1]; Award 1 mark for correct answer: 34 or 34.0 (%) [1].

Step 1: Multiply total collected fluid volume by the percentage of oil:
4 500 * (38 / 100) = 1 710 m3

Award 1 mark for correct numerical working: 4 500 * 0.38 [1]; Award 1 mark for correct value with unit: 1 710 m3 [1]; Reject answers lacking units or with incorrect units.

Step 1: Use the population density formula:
Population density = Total population / Total land area

Step 2: Substitute given values:
249 600 / 640 = 390 people per km2

Award 1 mark for correct division expression: 249 600 / 640 [1]; Award 1 mark for correct value: 390 (people per km2) [1].

Method 1:
Freshwater produced = 72 000 * 0.45 = 32 400 m3
Brine discharged = 72 000 - 32 400 = 39 600 m3

Method 2:
Brine percentage = 100% - 45% = 55%
Brine discharged = 72 000 * 0.55 = 39 600 m3

Award 1 mark for calculating freshwater volume (32 400) or brine fraction (0.55 / 55%) [1]; Award 1 mark for correct final volume: 39 600 (m3) [1].

Step 1: Calculate mass of copper:
85 000 * (0.64 / 100) = 544 tonnes

Award 1 mark for correct working: 85 000 * 0.0064 or 85 000 * (0.64 / 100) [1]; Award 1 mark for correct value and unit: 544 tonnes / t [1].

Step 1: Sum the counts from all five quadrats:
14 + 22 + 19 + 25 + 15 = 95 plants

Step 2: Divide by the number of quadrats:
95 / 5 = 19 plants per m2

Award 1 mark for total count of 95 or setting up sum divided by 5 [1]; Award 1 mark for correct mean: 19 (plants per m2) [1].

Step 1: Determine the reduction in soil loss:
48.0 - 7.2 = 40.8 tonnes

Step 2: Calculate the percentage reduction relative to Plot 1:
(40.8 / 48.0) * 100 = 85.0%

Award 1 mark for calculating reduction divided by initial value: (48.0 - 7.2) / 48.0 * 100 or 40.8 / 48.0 [1]; Award 1 mark for correct final value: 85 or 85.0 (%) [1].

1. Determine the decrease in forest cover:
$$\text{Decrease} = 84\,000\text{ ha} - 71\,400\text{ ha} = 12\,600\text{ ha}$$

2. Calculate the percentage decrease relative to the initial 2019 value:
$$\text{Percentage decrease} = \left(\frac{12\,600}{84\,000}\right) \times 100 = 15\%$$

Calculation of decrease: $84\,000 - 71\,400 = 12\,600$ [1];
Correct final answer: $15(\%)$ [1];
[Total: 1.8 marks (rounded to 2 in assessment records)]
[Guidance: Award 1 mark for correct method $\frac{12\,600}{84\,000} \times 100$ if arithmetic error is made. Award 2 marks for correct answer with no working shown.]

1. Formula for recovery rate:
$$\text{Recovery rate} = \left(\frac{\text{Volume of potable water produced}}{\text{Volume of seawater intake}}\right) \times 100$$

2. Substitute the given values:
$$\text{Recovery rate} = \left(\frac{18\,900\text{ m}^3}{45\,000\text{ m}^3}\right) \times 100 = 42\%$$

Correct substitution into formula: $\frac{18\,900}{45\,000} \times 100$ [1];
Correct final answer: $42(\%)$ [1];
[Total: 1.8 marks]
[Guidance: Allow ecf if correct division is shown but percentage conversion has a place-value error.]

1. Set up the ratio of Wind to Solar:
$$\text{Wind} : \text{Solar} = 2\,160 : 1\,440$$

2. Divide both terms by their greatest common divisor ($720$):
$$\frac{2\,160}{720} = 3, \quad \frac{1\,440}{720} = 2$$

3. Simplest whole-number ratio is $3 : 2$ (or $1.5 : 1$ if requested, but whole-number required = $3 : 2$).

Correct unsimplified ratio or common factor identification (e.g. $216 : 144$ or dividing by $720$) [1];
Correct simplest whole-number ratio: $3 : 2$ (or $3$ to $2$) [1];
[Guidance: Reject $1.5 : 1$ as whole numbers are specified. Reject inverted ratio $2 : 3$.]

1. Calculate the total number of beetles recorded across all 5 stations:
$$\text{Total} = 8 + 14 + 22 + 31 + 35 = 110$$

2. Divide by the number of sampling stations ($n = 5$):
$$\text{Mean} = \frac{110}{5} = 22\text{ beetles per station}$$

Sum of all counts shown: $8 + 14 + 22 + 31 + 35 = 110$ [1];
Correct mean value calculated: $22$ [1];
[Guidance: If total is incorrect due to an addition error, award 1 mark ecf for dividing their sum by 5.]

1. Calculate the absolute decrease in concentration:
$$\text{Decrease} = 0.85\text{ mg/dm}^3 - 0.17\text{ mg/dm}^3 = 0.68\text{ mg/dm}^3$$

2. Calculate the percentage reduction relative to Point A:
$$\text{Percentage reduction} = \left(\frac{0.68}{0.85}\right) \times 100 = 80\%$$

Correct subtraction: $0.85 - 0.17 = 0.68$ OR correct setup $\frac{0.85 - 0.17}{0.85} \times 100$ [1];
Correct final answer: $80(\%)$ [1];
[Guidance: Award 2 marks for correct answer without working.]

1. Formula for population density:
$$\text{Population density} = \frac{\text{Total population}}{\text{Land area in }\text{km}^2}$$

2. Substitute the values:
$$\text{Population density} = \frac{648\,000}{4\,500} = 144\text{ people per }\text{km}^2$$

Correct division setup: $\frac{648\,000}{4\,500}$ [1];
Correct answer: $144$ (people per $\text{km}^2$) [1];
[Guidance: Units not strictly penalized if omitted, but numerical value must be 144.]

1. Substitute the supplied figures into the equation:
$$\text{FCR} = \frac{720\text{ tonnes}}{480\text{ tonnes}}$$

2. Calculate the value:
$$\text{FCR} = 1.5$$

3. Value to one decimal place is $1.5$ (or $1.50$).

Correct substitution into formula: $\frac{720}{480}$ [1];
Correct final answer: $1.5$ [1];
[Guidance: Accept $1.50$. Reject $0.67$ / $\frac{480}{720}$ (inverted).]

1. Clear-felling removes vegetation cover and root networks that bind soil particles together.
2. Raindrops strike bare soil directly (loss of interception), dislodging soil particles (splash erosion).
3. Surface run-off washes loose topsoil downslope into river channels, causing sedimentation and siltation.
4. When sampling near fast-flowing water, safety precautions include wearing a life jacket, working in pairs, or using an extendable sampling container from a stable bank.

Clear-felling mechanism (max 2 marks):
- Loss of interception / tree canopy leaves bare soil exposed to raindrop impact;
- Loss of tree roots means soil particles are no longer bound / stabilised;
- Increased surface run-off transports / washes loose topsoil into river channels / water bodies;

Precaution (1 mark):
- Wear a life jacket / buoyancy aid / tether with safety rope;
- Sample from a secure / stable riverbank / use an extendable pole / do not enter deep water alone / work in pairs;
[Guidance: Reject 'be careful' without practical action. Total scaled to 2.8 marks.]

1. Run-off containing nitrate fertilizers causes rapid growth of algae on the river surface (algal bloom).
2. The dense layer of algae blocks sunlight from penetrating the water, preventing submerged aquatic plants from photosynthesising, causing them to die.
3. When the algae and plants die, populations of aerobic bacteria (decomposers) multiply rapidly as they feed on the organic material.
4. These bacteria use up large quantities of dissolved oxygen during aerobic respiration.
5. The water becomes deoxygenated (anoxic), leaving insufficient oxygen for fish to respire, resulting in fish mortality.

Award 1 mark for each valid linked point up to a maximum of 3 marks:
- Nitrates promote rapid algal growth / algal bloom / rapid plant growth;
- (Algal bloom) blocks sunlight, preventing photosynthesis of submerged plants / causing aquatic plants to die;
- Dead algae / plants are decomposed / broken down by bacteria / microorganisms;
- Bacteria / decomposers reproduce rapidly and consume dissolved oxygen in aerobic respiration;
- Water becomes deoxygenated / anoxic, leading to suffocation / death of fish (due to lack of oxygen for respiration);

Guidance: Do not accept 'algae use up all the oxygen when they grow'. The mark for oxygen depletion must be linked to bacterial decomposition / aerobic respiration.

1. Clearing trees removes the root network that binds the soil particles together and removes the tree canopy that intercepts rainfall.
2. Raindrops directly hit bare topsoil, loosening particles, and increased surface run-off washes loose soil into streams and rivers.
3. The sediment/silt is transported downstream into the coastal ocean.
4. Suspended sediment increases water turbidity and blocks sunlight, preventing symbiotic algae (zooxanthellae) in coral from photosynthesising.
5. Deposited silt physically blankets/smothers coral polyps, clogging their feeding structures and causing death.

Award 1 mark for each valid linked point up to a maximum of 3 marks:
- Removal of tree roots reduces soil binding / soil loses stability OR loss of tree canopy reduces rainfall interception;
- Surface run-off increases / bare soil is eroded / washed into rivers / waterways during rainfall;
- Soil / sediment / silt is transported into coastal waters / ocean;
- Silt / suspended particles block sunlight, reducing photosynthesis (by algae / zooxanthellae in coral);
- Sediment settles and smothers / blankets coral polyps / clogs feeding structures of coral;

Guidance: Accept 'turbidity increases' for blocking sunlight. Reject points relating to ocean acidification or oil pollution.

The independent variable plotted on the horizontal axis ($x$-axis) is 'Distance along transect / m' and the dependent variable plotted on the vertical axis ($y$-axis) is 'Canopy cover / %'.

For the missing data point at a distance of $60\text{ m}$, the canopy cover is $70\%$.

Therefore, the coordinate pair is $(60, 70)$.

$(60, 70)$ / $x = 60$ and $y = 70$;

[Guidance: Accept $(60\text{ m}, 70\%)$ or equivalent clear identification of $x$ and $y$ values. Reject reversed coordinates $(70, 60)$].

From the data table, sampling station Y has a mean sulfur dioxide concentration of $35\text{ }\mu\text{g m}^{-3}$.

On the vertical axis labelled 'Mean $\text{SO}_2$ concentration / $\mu\text{g m}^{-3}$', the bar for station Y must be drawn to a height of $35$ (or $35\text{ }\mu\text{g m}^{-3}$).

$35$ / $35\text{ }\mu\text{g m}^{-3}$ / $35\text{ }\mu\text{g/m}^3$;

[Guidance: Accept 35 without units since the quantity is defined by the axis label. Reject any other numerical value].