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

(a) Any two from: landfilling/backfilling the open pit; landscaping/re-profiling the slopes to prevent soil erosion; revegetation/planting trees or grass to stabilize the soil; creating a water reservoir/lake for recreation or wildlife habitat.

(b) Any two from: leaching of toxic chemicals/heavy metals into surrounding groundwater; production of greenhouse gases (such as methane and carbon dioxide) from decomposing organic waste; unpleasant odors affecting nearby residential areas; attraction of pests and disease vectors (such as rodents or insects).

(c) Bioremediation uses biological agents like microorganisms (bacteria or fungi) or plants to degrade, accumulate, or neutralize hazardous pollutants in toxic mining wastes. This process converts harmful heavy metals or organic contaminants into less toxic or inert forms, helping to restore the soil health safely.

(a) [2 marks] 1 mark for each valid method.
Accept: backfilling, capping/landfilling, revegetation / planting trees / grass, re-grading/re-profiling slopes, creation of recreational lakes or wetlands.

(b) [2 marks] 1 mark for each valid problem.
Accept: leachate production / groundwater contamination, greenhouse gas emissions (methane/CO2), visual pollution, noise/dust, pests/scavengers, unpleasant smells.

(c) [2 marks]
1 mark for identifying the use of living organisms (such as bacteria, fungi, yeast, or plants) to target pollutants.
1 mark for explaining that they absorb, break down, or convert toxic heavy metals/chemicals into non-toxic/less harmful forms.

(a) Maximum sustainable yield (MSY) is the largest average catch that can be captured from a stock under existing environmental conditions without depleting the population over the long term.

(b) (i) Year 3. The actual catch (155,000 tonnes) exceeded the Maximum Sustainable Yield (120,000 tonnes) by 35,000 tonnes, which is the largest overshoot of MSY among all the years shown (Year 2 only exceeded MSY by 25,000 tonnes).

(ii) Percentage decrease = \frac{\text{Change in MSY}}{\text{Original MSY}} \times 100 = \frac{150,000 - 100,000}{150,000} \times 100 = \frac{50,000}{150,000} \times 100 = 33.3\%.

(c) Any one from: establishing marine protected areas (no-take zones); enforcing minimum mesh size limits on nets (to allow immature fish to escape); implementing closed seasons during spawning periods; reducing the number of active fishing vessels (decommissioning boats).

(a) [1 mark] Award 1 mark for a definition mentioning the maximum harvest/catch of fish that can be sustained over time without reducing the long-term stock level.

(b) (i) [2 marks]
1 mark for identifying Year 3.
1 mark for a supporting calculation or comparative reasoning (e.g., Year 3 exceeded MSY by 35,000 tonnes, which is greater than the 25,000 tonnes in Year 2).

(ii) [2 marks]
1 mark for correct working: \frac{150,000 - 100,000}{150,000} \times 100.
1 mark for correct calculation: 33.3% (accept 33% or 33.33%).

(c) [1 mark] Award 1 mark for any valid fishery management strategy that is not a quota (e.g., closed seasons, mesh size restrictions, marine reserves, vessel limits, licensing).

(a) Contour ploughing involves ploughing across/perpendicular to the slope instead of up and down it. This creates horizontal furrows and ridges that trap water, slowing down surface runoff and encouraging it to soak into the ground rather than carrying topsoil away.

(b) Windbreaks (rows of trees or tall shrubs) reduce wind speed/velocity at the ground level. Since wind erosion depends heavily on wind energy, lowering wind speeds prevents the detachment and transport of dry, loose topsoil particles.

(c) 1. Over-irrigation (especially with water containing dissolved mineral salts), raising the water table.
2. Inadequate drainage systems coupled with high evaporation rates, which draws saline groundwater up to the surface where the water evaporates and leaves behind toxic crusts of salt.

(a) [2 marks]
1 mark for explaining that ploughing occurs across / parallel to the contours / perpendicular to the slope direction (not up and down).
1 mark for explaining that the ridges/furrows act as barriers that slow surface runoff / increase water infiltration / trap moving soil.

(b) [2 marks]
1 mark for stating that the lines of trees/shrubs reduce the speed/force of the wind.
1 mark for explaining that this reduction in wind speed prevents topsoil particles from being lifted, blown, or swept away.

(c) [2 marks] Award 1 mark for each valid practice up to a maximum of 2.
Accept: excessive irrigation, lack of proper sub-surface drainage, using mineral-rich/brackish water for irrigation, land clearing (which raises saline water tables).

(a) Graph plotting details:
- Vertical axis: labelled 'Concentration of \(\text{NO}_2\) / \(\mu\text{g/m}^3\)' with a linear scale from 0 to at least 60.
- Horizontal axis: labelled 'Time of day / hours' with a linear scale from 06:00 to 18:00.
- All 7 points plotted accurately.
- Points joined with a neat, continuous line.

(b) Peaks occur at 08:00 (\(54 \mu\text{g/m}^3\)) and 18:00 (\(60 \mu\text{g/m}^3\)). These correspond to morning and evening rush hours when road traffic volume is highest.

(c) During a temperature inversion, a layer of warm air sits above a layer of cold air near the ground. This prevents the normal upward convection currents, trapping vehicle pollutants (like \(\text{NO}_2\)) close to the surface where they accumulate.

(d) 1. Implementing a Low Emission Zone (LEZ) / charging high-emission vehicles.
2. Investing in and promoting public electric transit / expanding cycling infrastructure.
3. Pedestrianising busy commercial streets / restricting private car access.

(a) [4 marks total]
- Axes correctly labelled with units [1]
- Suitable linear scale that uses more than half the grid space [1]
- All data points plotted accurately [1]
- Points joined together with a neat line [1]

(b) [2 marks total]
- Correct identification of peaks at 08:00 and 18:00 [1]
- Linked to increased vehicle volume during commuter/rush hours [1]

(c) [2 marks total]
- Warm air layer acts as a 'lid' over cooler air [1]
- Prevents dispersal / traps pollutants near the ground [1]

(d) [3 marks total]
- Any three from: vehicle bans/pedestrianisation; low emission zones; congestion charging; improving public transport; cycle networks; park-and-ride schemes. [1 mark per valid point]

(a) Calculation:
\(\text{Increase} = 32\% - 12\% = 20\%\)
\(\text{Percentage increase} = \frac{20}{12} \times 100 = 166.7\%\) (accept 167% or 166.67%)

(b) Bar chart requirements:
- Vertical axis: 'Percentage of coral composition / %' (scale 0 to 50).
- Horizontal axis: 'Coral group' with categories (Branching, Plate, Massive).
- Bars plotted accurately to heights: 45%, 35%, 20%.
- Bars must be of equal width, with distinct gaps between them.

(c) 1. Rising ocean temperatures trigger coral bleaching (loss of symbiotic zooxanthellae algae).
2. Ocean acidification (due to higher absorbed carbon dioxide) lowers pH, hindering corals from building their calcium carbonate skeletons.

(d) 1. Designate Marine Protected Areas (MPAs) where fishing and tourism are restricted.
2. Restrict destructive fishing practices (e.g., banning bottom trawling, dynamite, or cyanide fishing).
3. Install permanent mooring buoys to prevent damage from boat anchors.

(a) [2 marks total]
- Correct calculation setup showing change over initial value (e.g., \(\frac{20}{12} \times 100\)) [1]
- Correct final calculation of 166.7% or 167% [1]

(b) [4 marks total]
- Correctly labelled axes with units [1]
- Sensible linear scale on vertical axis [1]
- All three bars plotted to correct height [1]
- Bars of equal width and separated by clear gaps [1]

(c) [2 marks total]
- Rising temperatures leading to bleaching [1]
- Acidification reducing skeletal growth / calcification [1]

(d) [3 marks total]
- Any three from: establishing MPAs; quotas on fishing; bans on anchors / installing mooring buoys; bans on dynamite/cyanide fishing; restricting visitor numbers. [1 mark per valid point]

(a) Calculation:
\(\frac{0.88}{0.22} = 4\)
Therefore, it is 4 times greater.

(b) Bar chart requirements:
- Vertical axis: 'Phosphate concentration / mg/L' with a linear scale from 0 to 1.0.
- Horizontal axis: 'Land-use zone' (Zone X, Zone Y, Zone Z).
- Bars plotted accurately: Zone X = 0.05, Zone Y = 0.22, Zone Z = 0.88.
- Separate bars of equal width, with distinct spacing.

(c) 1. High nutrient run-off triggers rapid growth of algae (algal bloom) on the water surface, blocking sunlight.
2. Submerged plants cannot photosynthesise and die; bacteria decompose this dead vegetation.
3. The decomposing bacteria multiply rapidly, consuming dissolved oxygen, leading to anoxia/hypoxia, causing fish to suffocate and die.

(d) 1. Planting riparian buffer zones (vegetated strips/hedgerows along waterways) to absorb nutrient run-off.
2. Practising precision fertilizer application (applying exact amounts during dry weather to avoid leaching).

(a) [2 marks total]
- Correct calculation setup showing division of Zone Z by Zone Y [1]
- Correct final answer of 4 [1]

(b) [4 marks total]
- Vertical axis labelled with correct parameter and unit (mg/L) [1]
- Linear scale starting at zero, using at least half the graph grid [1]
- All three bars plotted to correct heights [1]
- Neat bars of equal width with clear, consistent spacing [1]

(c) [3 marks total]
- Algal bloom blocks sunlight, causing plants below to die [1]
- Decomposers/bacteria feed on dead plant matter and multiply [1]
- Bacteria deplete dissolved oxygen in respiration, causing fish death [1]

(d) [2 marks total]
- Any two from: planting riparian buffer strips; using slow-release fertilizers; applying fertilizers only in dry weather conditions; using soil conservation techniques to prevent erosion. [1 mark per valid point]

(a) The concentration of microplastics increases as we move up the trophic levels of the food chain. The lowest concentration is found in the producers (phytoplankton) at 12 particles/kg, while the highest concentration is found in the apex predators (harbour seals) at 3150 particles/kg, representing a massive accumulation over trophic steps.

(b) This is caused by bioaccumulation and biomagnification. First, microplastics are non-biodegradable and chemical-resistant, meaning they remain in the tissues of organisms without being digested, broken down, or excreted. Second, organisms at higher trophic levels (like herring and seals) must consume many times their own body mass in prey over their lifetimes to meet energy demands. This means the microplastics from thousands of lower-level organisms are consolidated and concentrated inside the body of a single predator.

(c) 1. Mechanical blockage of the digestive system, leading to a false sensation of fullness, reduced food intake, and eventual starvation.
2. Chemical toxicity, as microplastics absorb organic pollutants (like PCBs) from seawater and contain harmful chemical additives that cause endocrine disruption, reproductive failure, or tissue inflammation when absorbed.

(d) 1. Implementing bans or heavy taxes on single-use plastic items (e.g., bags, straws, packaging) to reduce the volume of plastic produced.
2. Improving waste collection and recycling infrastructure, ensuring landfills are secured and waste does not escape into waterways.
3. Introducing container deposit-return schemes to incentivize recycling and reduce public littering.

(a)
- Award 1 mark for stating that microplastic concentration increases with higher trophic levels / along the food chain.
- Award 1 mark for citing contrasting data (e.g., lowest at 12 particles/kg in phytoplankton and highest at 3150 particles/kg in harbour seals).

(b)
- Award 0.5 marks for identifying 'biomagnification' or 'bioaccumulation'.
- Award 1 mark for explaining that microplastics are non-biodegradable / cannot be easily excreted or metabolized.
- Award 1 mark for explaining that predators must consume large quantities of prey over time.
- Award 1 mark for linking this to the concentration of plastics increasing at each successive trophic step.

(c)
- Award 1 mark per valid impact (max 2):
- Physical damage / laceration of the gut / digestive tract blockage.
- False sense of satiety / starvation.
- Bioaccumulation of absorbed chemical toxins (endocrine disruptors / carcinogens).
- Reduced reproductive success / growth rates.

(d)
- Award 1 mark per valid government policy (max 3):
- Bans or levies on single-use plastics.
- Investment in modern recycling plants / advanced municipal waste capture.
- Deposit-return container legislation.
- Incentives for developing biodegradable alternative materials.
- Public education campaigns on waste sorting and ocean stewardship.

(a) Step 1: Calculate the absolute reduction in soil loss:
$$45.2 \text{ tonnes/ha/year} - 12.8 \text{ tonnes/ha/year} = 32.4 \text{ tonnes/ha/year}$$

Step 2: Calculate the percentage reduction relative to Strategy A:
$$\text{Percentage Reduction} = \left( \frac{32.4}{45.2} \right) \times 100 = 71.681...\%$$
Rounded to 1 decimal place = 71.7% (or 72% as a whole number).

(b) Contour ploughing involves ploughing across the slope, perpendicular to the flow of water. This creates horizontal ridges and furrows that act as physical barriers, slowing down surface runoff and allowing more water to infiltrate the soil. Cover crops work in synergy by providing leaf canopy cover that breaks the kinetic energy of raindrops, preventing splash erosion. Simultaneously, their extensive root systems bind the soil particles together, dramatically increasing the soil's resistance to being washed away by the slowed runoff.

(c) 1. Windbreaks (planting lines of trees around fields to reduce wind velocity and wind erosion).
2. Terracing (cutting steps into steep slopes to dramatically reduce water runoff speed).

(d) 1. High initial labor or capital requirement to construct earth bunds/terraces on slopes.
2. Lack of spare capital to purchase specialized cover crop seeds, combined with the risk of using arable land for cover crops rather than immediate food-producing cash crops.

(a)
- Award 1 mark for showing correct working formula or subtraction: (45.2 - 12.8) / 45.2.
- Award 1 mark for the correct raw calculation result: 0.7168 or 71.68%.
- Award 0.5 marks for rounding correctly to either 71.7% or 72% with the percentage symbol.

(b)
- Award up to 2 marks for explaining contour ploughing:
- Ploughing across the slope/perpendicular to water flow (1).
- Furrows act as micro-dams, reducing the speed of surface runoff and increasing infiltration (1).
- Award up to 2 marks for explaining cover crops:
- Plants cover the bare soil surface, reducing soil splash from rain impact (1).
- Roots bind soil particles, making it harder for running water to transport soil (1).

(c)
- Award 1 mark per correct practice (max 2):
- Terracing.
- Windbreaks / shelterbelts.
- Conservation tillage / zero-till.
- Organic mulching.
- Crop rotation with legumes.
- Addition of organic matter (manure/compost).

(d)
- Award 1 mark per valid constraint (max 2):
- High cost / lack of capital to purchase cover crop seeds.
- Lack of heavy machinery or high physical labor requirements to build earth bunds.
- Loss of cultivable area due to bund placement.
- Lack of training, awareness, or extension services explaining the benefits.

A balanced level 3 response should evaluate both sides of the argument before reaching a clear, justified conclusion. Organic farming methods, such as crop rotation, composting, and biological pest control, are highly sustainable. They prevent soil degradation, reduce chemical runoff into freshwater systems (thus avoiding eutrophication), and promote biodiversity. However, organic agriculture generally produces lower crop yields per hectare compared to conventional farming that utilizes synthetic fertilizers and chemical pesticides. To feed a rapidly growing global population, expanding organic agriculture to a global scale would require clearing massive areas of natural ecosystems for farmland, which accelerates deforestation and biodiversity loss. Consequently, many experts advocate for an integrated system—such as Integrated Pest Management (IPM) and conservation tillage—which merges the ecological benefits of organic farming with the yield efficiency of modern agricultural technology.

Level 3 [5-6 marks]
A coherent response is given that develops and supports the candidate's conclusion using relevant details and examples. Good responses present a balanced evaluation of the statement, comparing the environmental sustainability of organic methods against the yield requirements of a growing population.

Level 2 [3-4 marks]
Development and support of the conclusion is evident, though the response may lack some coherence and/or detail. Candidates evaluate the statement but the response may not be fully balanced (focusing mostly on organic benefits or mostly on yield limitations).

Level 1 [1-2 marks]
The response is limited in development and/or support. It may be in the form of a simple list of organic farming features without direct evaluation of global food demand or sustainability.

[0 marks]
No response or no creditable response.

Indicative content:
Arguments in favor of organic farming:
- Uses organic fertilizers (manure, compost) which improve soil structure and water-holding capacity.
- Avoids synthetic chemical fertilizers, preventing nutrient runoff and subsequent eutrophication of aquatic ecosystems.
- Avoids chemical pesticides, protecting non-target organisms like pollinators and maintaining biodiversity.
- Minimizes toxic bioaccumulation in food chains.

Arguments against organic farming as the sole solution:
- Typically results in lower crop yields per unit area compared to intensive conventional methods.
- Requires significantly more land to produce the same quantity of food, potentially driving deforestation and habitat destruction.
- More labor-intensive, which increases the cost of food production and makes food less affordable for lower-income populations.
- Organic fertilizers release nutrients slowly, which may not meet the rapid demand of crops during critical growing phases.