Biodiversity and the Effect of Human Interaction on Ecosystems

Biodiversity is the variety of all the different species of organisms on Earth, or within a specific ecosystem.

It's measured at three levels:

Species diversity — the number of different species in an area. A UK woodland might have hundreds; a UK chalk grassland thousands; a coral reef tens of thousands.

Genetic diversity (within a species) — the variation in the gene pool of one species. A small, inbred population has low genetic diversity and is vulnerable to disease or environmental change.

Ecosystem diversity — the variety of different ecosystems in a region. The UK has woodlands, moors, peat bogs, hedgerows, rivers, rocky shores, salt marshes, urban habitats — high ecosystem diversity for a small country.

High biodiversity = more stable ecosystem. This is one of the central exam points of the topic. The reasons:

1. Many alternative pathways. In a complex food web, most predators eat several prey species. If one prey species declines, predators switch to alternatives — the food web absorbs the change rather than collapsing.

2. Reduced dependence on any single species. Pollinators rely on many flowers; flowers rely on many pollinators. No single species is a single point of failure.

3. Multiple decomposers. Many different bacteria and fungi break down different materials at different rates, so dead matter is always being recycled.

4. Genetic diversity within species. If a disease arrives, some individuals will have alleles that confer resistance, so the population survives even if numbers fall.

5. Resilience to environmental change. With many species adapted to slightly different conditions, the community has more chance of including some species suited to new conditions.

Conversely, low biodiversity = fragile. Monoculture crops (a whole field of one variety of wheat) are vulnerable: one disease, one pest or one bad year can devastate the entire harvest. The 19th-century Irish potato famine is the most famous example — millions starved when one fungal disease (potato blight) destroyed the single potato variety grown across the country.

UK example. Native English oak woodland is highly biodiverse — over 280 insect species, plus fungi, birds, mammals and other plants. A plantation of single-species Sitka spruce is very low biodiversity and supports a fraction of that life. The oak woodland is much more stable.

Biodiversity matters to humans for very practical reasons:

1. Food. Almost all our food comes ultimately from biodiversity. The wild ancestors of crops and livestock are a gene bank for future breeding. Pollinators (bees, hoverflies, butterflies) are essential for apples, strawberries, oilseed rape and many other UK crops.

2. Medicine. Many drugs come from natural products — aspirin from willow bark; penicillin from a fungus; the breast cancer drug paclitaxel from yew trees; metformin (diabetes) from French lilac. Most species haven't been screened for medical use.

3. Raw materials. Wood, cotton, leather, rubber, paper — all from biodiversity.

4. Ecosystem services. Largely invisible but vital:

• Pollination — UK farming depends on wild pollinators worth billions.
• Water purification — wetlands and forests clean water naturally.
• Carbon storage — UK peat bogs hold more carbon than UK forests; protecting them is climate action.
• Soil formation — earthworms and microbes create the soil that grows our food.
• Flood control — natural floodplains and wetlands buffer flooding.

5. Cultural and recreational value. Wildlife enriches our lives and supports tourism (UK nature tourism is worth billions annually).

The UK situation. The State of Nature report (2023) found about half of UK wildlife species have declined since 1970, with one in six species at risk of extinction. The UK ranks near the bottom of G7 countries for ecosystem intactness — a stark exam fact.

Modern threats to biodiversity (largely from human activity) are sometimes summarised as HIPPO: Habitat loss, Invasive species, Pollution, Population (human), Overexploitation.

Habitat destruction. Deforestation (Amazon, SE Asia), wetland drainage, hedge removal, urban sprawl. UK lost ~50% of its hedgerows in the 20th century. The single biggest cause of biodiversity loss worldwide.

Climate change. Covered in 4.7.2.4 (Biology only). Warming shifts species ranges; sea-level rise drowns coastal habitats; ocean acidification damages corals and shellfish.

Pollution. Sewage, fertiliser runoff, plastics, oil spills, pesticides. Neonicotinoid insecticides have been linked to bee declines; agricultural runoff feeds algal blooms in UK rivers.

Overexploitation. Overfishing (Atlantic cod), overhunting (UK once had wolves, lynx, brown bears — all hunted to extinction), illegal wildlife trade.

Introduced (invasive) species. Grey squirrel vs red squirrel; American mink vs water vole; rhododendron vs native UK woodland plants; ash dieback fungus — all introductions that damaged biodiversity.

Spec link. This subtopic links forward to 4.7.3.2 (waste management) and back to 4.7.1.3 (biotic factors including invasive species). Examiners often combine the topics in extended-answer questions.

Conservation responses. Habitat protection (SSSIs, National Parks), species recovery programmes (red kite reintroduction), wildlife corridors, sustainable farming and fishing, international agreements.

Two things drive rising pollution:

1. Human population growth. World population passed 8 billion in 2022 and is projected to peak around 10 billion. More people = more food, water, energy and consumer goods — and more waste.

2. Rising standards of living. Average per-person consumption has risen sharply. We eat more meat, fly more, own more electronics, buy more clothes and waste more food than at any point in history. Each person now generates more waste than they did 50 years ago.

The combination means total waste generation is rising much faster than population alone. UK statistics: each person generates about 400 kg of household waste per year (much of which goes to landfill or incineration).

Types of waste:

• Sewage and grey water (household sewage and runoff).
• Agricultural waste (fertilisers, pesticides, livestock manure).
• Industrial waste (factory effluent, heavy metals, plastics).
• Domestic waste (food, packaging, electronics, batteries).
• Atmospheric waste (CO₂, SO₂, NOₓ, soot from burning fuels).

If waste is not properly handled it ends up polluting water, air or land — with knock-on effects for biodiversity.

Sources of water pollution:

• Sewage — raw sewage from poorly treated wastewater contains pathogens and organic matter.
• Fertilisers — nitrate and phosphate from farmland runoff.
• Toxic chemicals — heavy metals, pesticides, industrial effluent.
• Plastics — especially microplastics now found in every UK river.
• Oil spills — from shipping and offshore platforms.

How sewage kills fish (eutrophication).

1. Sewage / fertiliser adds nitrate + phosphate to a river or lake.
2. Algae and water plants grow rapidly — an algal bloom covers the surface.
3. Algae block light; plants below die.
4. Dead algae and plants are decomposed by bacteria, which respire aerobically and use up dissolved oxygen.
5. Dissolved O₂ falls below the level fish (e.g. UK brown trout) need.
6. Fish suffocate and die.

This is the classic UK chain: fertiliser → algal bloom → low O₂ → dead fish. Examiners love it.

Other water-pollution effects.

• Heavy metals (mercury, cadmium) accumulate through food chains (bioaccumulation), poisoning top predators.
• Pesticides like DDT thinned eggshells of UK peregrine falcons in the 1960s, almost wiping them out; banning DDT allowed recovery.
• Plastics tangle marine life and break into microplastics that enter food chains.

Current UK issue. Water companies discharged untreated sewage into UK rivers and seas hundreds of thousands of times in 2023, sparking public outcry and tougher Environment Agency rules.

Sources of air pollution:

• Combustion of fossil fuels in power stations, vehicles and home heating.
• Smoke (particulates) from diesel engines, wood stoves and wildfires.
• Sulfur dioxide (SO₂) from burning sulfur-containing coal.
• Nitrogen oxides (NOₓ) from high-temperature combustion in vehicles.

Effects on humans.

• Particulates (PM2.5, PM10) penetrate deep into lungs → asthma, bronchitis, cardiovascular disease, increased mortality.
• Long-term UK exposure linked to ~30,000 early deaths a year.

Effects on ecosystems — acid rain.

• SO₂ and NOₓ dissolve in atmospheric water to form sulfuric and nitric acid.
• Rain becomes acidic (pH 4–5, sometimes lower).
• Acid rain damages tree leaves, acidifies soils and freshwater, leaching aluminium from soil into rivers.
• UK / Scandinavian lakes were heavily damaged in the 1970s–80s; SO₂ scrubbing on power stations has greatly reduced this since.

Effects on biodiversity.

• Sensitive species disappear first — many UK lichens are bioindicators of clean air.
• Acidification of lakes killed UK fish and invertebrates in upland areas.
• Smog harms plant photosynthesis by coating leaves with particulates.

Modern UK issue. Urban NO₂ from diesel vehicles still exceeds legal limits in many UK cities, leading to Ultra Low Emission Zones in London and other cities.

Sources of land pollution:

• Landfill — billions of tonnes of household and industrial waste buried each year. Decomposes slowly, releases methane and toxic leachate.
• Toxic chemicals — heavy metals from old industry; PCBs and dioxins; mining waste.
• Pesticides — broad-spectrum chemicals kill beneficial insects as well as pests; reduce food for birds and bats.
• Herbicides — kill weeds that pollinators depend on.
• Plastics — discarded plastics persist for centuries; microplastics now found in every UK soil tested.
• Sewage sludge spread on farmland — useful nutrients but also persistent organic pollutants.

Effects on biodiversity.

• Habitat destruction — landfill sites replace natural habitat.
• Soil organism deaths — heavy metals and pesticides kill earthworms, beetles, microbes; soil structure and decomposition slow down.
• Food chain effects — pesticide-killed insects mean less food for birds (link to UK farmland bird declines).
• Bioaccumulation — persistent chemicals build up in top predators (the famous DDT-and-peregrine story is partly a land/water example).

UK example: peat bog destruction. Peat has been dug from UK upland bogs for horticulture and fuel for decades. Drained, dug-up peat bogs release stored carbon as CO₂, lose biodiversity (sphagnum moss, sundew, peat-bog insects, golden plover) and shrink habitat. The government has now restricted peat sales in garden compost in England — a recent biodiversity-protection policy.

Reducing land pollution.

• Recycling and composting (UK recycling rate ~45%).
• Banning single-use plastics.
• Switching to integrated pest management (less pesticide).
• Restoring peat bogs and abandoned industrial land.

Humans need land for almost every part of modern life — homes, food production, raw materials, and waste disposal. Each use takes away space that could otherwise support wild plants and animals.

The AQA specification highlights four main uses that reduce land for other organisms:

1. Building. Towns, cities, roads, railways and factories cover the ground in concrete and tarmac. Once built on, the land is effectively lost to most native species. In the UK, urban expansion swallows around 7,000 hectares of green space every year, mainly on the edges of cities.

2. Quarrying. Removing stone, sand, gravel and chalk for construction strips topsoil, destroys habitats and leaves large pits that fill with water or rubble. The Mendip Hills and parts of the Peak District show how quarries can dominate the landscape.

3. Farming. Around 70% of UK land is farmed — for crops (about 25%) or pasture for livestock (about 45%). Intensive agriculture removes hedgerows, drains wetlands and replaces species-rich grasslands with monocultures of wheat, barley or grass.

4. Dumping waste. Landfill sites bury rubbish, leaching chemicals into soil and water and producing methane (a greenhouse gas). Even with modern recycling, the UK still sends around 7 million tonnes of waste to landfill each year.

Why this matters. Every patch of land used by humans is a patch unavailable to biodiversity. As habitats shrink and fragment, populations of native species fall — bees, hedgehogs, farmland birds and butterflies are all in long-term decline across the UK.

Peat is partly decomposed plant material that builds up over thousands of years in waterlogged, acidic conditions. Peat bogs are the wetlands where this happens — found in upland UK areas (the Pennines, Dartmoor, the Flow Country of Scotland) and across northern Europe.

Why peat bogs are special.

• They store huge amounts of carbon locked in undecomposed plants. UK peatlands store around 3 billion tonnes of carbon — more than all UK forests combined.
• They are home to rare and specialised species — sundew (a carnivorous plant), bog mosses (sphagnum), curlew, golden plover, large heath butterflies.
• They regulate water — releasing it slowly to streams, reducing flooding downstream.

Why peat bogs are being destroyed.

• Peat is dug up and sold as compost for gardens and commercial growing.
• Bogs are drained for sheep farming, forestry or wind farms.
• Some are burned (deliberate moor management for grouse shooting).

The double environmental impact.

1. Biodiversity loss — rare species disappear when their habitat is dug up.
2. CO₂ release — once exposed to air, the stored carbon decomposes and releases CO₂, adding to global warming. A single hectare of damaged peatland can emit several tonnes of CO₂ a year.

The peat-free movement. UK garden centres and major retailers have committed to phasing out peat compost. From 2024, peat compost sales to amateur gardeners are banned in England, with a commercial ban planned for 2030. Look for 'peat-free' labels on compost — it's an easy household action against habitat loss.

Evaluation questions on AQA exam papers ask you to weigh costs against benefits — not to pick a side.

Example: a new housing estate on green-belt land.

Benefit (for humans)	Cost (for wildlife/environment)
More homes — helps housing shortage	Habitat destroyed; species lost
Local jobs in construction	Run-off pollutes streams
Tax revenue for council	Permanent — concrete cannot easily be reversed
Closer to existing infrastructure	Carbon emissions from construction

Example: extracting peat for compost.

Benefit	Cost
Cheaper compost for gardeners	Releases stored CO₂
Local jobs at extraction sites	Rare habitat destroyed
Useful product for horticulture	Peat takes 1000+ years to form — not renewable

How to write an evaluation answer.

1. Give at least one benefit of the human activity.
2. Give at least one cost to the environment / biodiversity.
3. Reach a reasoned conclusion — e.g. 'on balance, the loss of irreplaceable peat is too high a cost when peat-free alternatives exist'.

Examiner reports stress that conclusions must be justified — don't just state an opinion. Link back to specific points you've made.

Deforestation is the large-scale removal of trees, usually by cutting and burning. In the past 50 years, an area of tropical forest larger than Western Europe has been cleared. AQA focuses on the tropics because that's where deforestation is fastest and the consequences worst.

The AQA-specified drivers:

1. Cattle (beef ranching). Tropical land — especially in Brazil's Amazon basin — is cleared and turned into grass pasture for beef cattle. Most of the meat is exported (to the EU, US and China). Cattle is the single biggest cause of Amazon deforestation.

2. Rice paddies. Rice is the staple food for over half the world's population. Rice grows in flooded fields ('paddies') and these are often created by clearing forest in South and South-East Asia (Indonesia, Thailand, Vietnam).

3. Biofuel crops. Biofuels are fuels made from plant material — for example, ethanol from sugar cane (Brazil) or biodiesel from palm oil and soya. Although biofuels are 'renewable', growing them on cleared forest land cancels out most of the carbon savings.

4. Palm oil plantations. Palm oil is in around half the products on a UK supermarket shelf (margarine, soap, biscuits, shampoo, processed food). Demand is huge and growing. Plantations have replaced vast areas of rainforest in Indonesia and Malaysia, the world's biggest producers.

5. Timber (logging). Hardwoods (mahogany, teak) are sold for furniture and construction. Even 'selective' logging damages the forest around the cut trees and opens roads that lead to further clearance.

Why tropical forests are targeted.

• Rapid tree growth → quick payback for ranchers/growers.
• Often government-owned land sold cheaply.
• Weak enforcement of forest laws in some countries.
• Global demand from richer nations (UK supermarkets included).

AQA wants you to link each consequence to the cause. The three big consequences are:

1. Loss of biodiversity. Tropical forests are the most biodiverse habitats on Earth. The Amazon alone contains an estimated 10% of all species known to science. When the forest is cleared:

• Habitats are destroyed → species lose nests, food, shelter.
• Specialised species (frogs, orchids, monkeys, insects) cannot survive in cleared land.
• Many become extinct before they have even been discovered or studied.
• The loss is permanent — you cannot 're-grow' an evolved tropical ecosystem.

2. CO₂ released into the atmosphere. Trees lock up carbon in their wood as they grow (carbon from CO₂ absorbed by photosynthesis). When trees are burned or left to rot, that carbon combines with oxygen and is released as CO₂. This adds to the greenhouse effect and accelerates global warming.

Approximately 10–15% of all human CO₂ emissions globally come from deforestation — more than the entire global transport sector except aviation.

3. Less CO₂ uptake in the future. Living trees absorb CO₂ from the atmosphere during photosynthesis. Once a forest is cut down, that 'carbon sink' is lost — there are fewer trees to remove future emissions. This is a 'positive feedback loop': less forest → more CO₂ stays in the atmosphere → more warming → further stress on remaining forests.

Other knock-on effects (good to mention for top-band marks):

• Soil erosion — without tree roots, tropical soils wash away in heavy rain.
• Disrupted water cycle — trees transpire huge volumes of water; without them rainfall patterns shift.
• Local communities — indigenous peoples lose their land and culture.

Government / international action.

• Protected forest reserves (e.g. parts of the Amazon, Borneo's Tanjung Puting).
• Satellite monitoring to spot illegal clearing in near real time.
• Trade agreements that ban deforestation-linked imports (UK Environment Act 2021 requires UK businesses to prove products are deforestation-free).

Industry action.

• Roundtable on Sustainable Palm Oil (RSPO) — certifies palm oil grown without rainforest clearing. Look for the RSPO logo on UK products.
• Forest Stewardship Council (FSC) — certifies timber and paper from sustainable forests.
• Major UK supermarkets (Tesco, Sainsbury's, M&S) have pledged 'deforestation-free' supply chains by 2025.

Reforestation (replanting). Planting new trees can absorb CO₂ and restore some habitat. BUT — plantations of one species are NOT the same as natural forest. They have low biodiversity and lock away less carbon than mature rainforest.

Consumer choices (UK GCSE-relevant).

• Eating less beef (the biggest deforestation driver).
• Choosing RSPO-certified palm oil products.
• Buying FSC-certified wood and paper.
• Supporting rainforest charities (WWF, Rainforest Alliance).

Rethinking biofuels. First-generation biofuels (made from food crops on cleared land) often make things worse. Newer biofuels from agricultural waste or algae avoid this problem and are an active research area.

Earth's atmosphere contains gases that allow visible light from the Sun to pass through but absorb infrared radiation that the warmed Earth emits back. These gases — including carbon dioxide (CO₂), methane (CH₄) and water vapour — act like the glass in a greenhouse, trapping heat and keeping Earth warm enough for life. This is the natural greenhouse effect.

The problem is that human activities have massively increased the concentration of CO₂ and methane in the atmosphere over the past 200 years.

Carbon dioxide (CO₂) — sources:

• Burning fossil fuels (coal, oil, natural gas) for electricity, transport, heating.
• Deforestation (burning trees releases stored carbon; fewer trees means less uptake).
• Cement manufacture (chemical breakdown of limestone releases CO₂).

CO₂ has risen from ~280 ppm before the industrial revolution to over 420 ppm in 2024 — a 50% increase.

Methane (CH₄) — sources:

• Cattle — methane is a by-product of digestion in cows and sheep (released by burping).
• Rice paddies — flooded fields support methane-producing bacteria.
• Landfill — waste rotting without oxygen releases methane.
• Fossil fuel extraction — leaks from gas pipelines and oil wells.

Methane is shorter-lived in the atmosphere (~12 years vs 100+ for CO₂) but molecule-for-molecule is around 25 times more powerful at trapping heat over a 100-year period.

AQA lists four key biological consequences to learn:

1. Change in species distribution. As regions warm, species move toward the poles (or up mountains) to stay in their preferred temperature range. In the UK:

• The comma butterfly has shifted ~200 km north since 1980.
• Dartford warbler (a heat-loving bird) is now nesting in Yorkshire — unheard of 50 years ago.
• Beech trees are being out-competed by warmer-climate species in southern England.

2. Loss of habitat. Some habitats simply disappear when conditions change:

• Arctic sea ice is shrinking — polar bears, walruses and seals losing hunting grounds.
• Coral reefs bleach and die at higher water temperatures.
• High mountain habitats — alpine species have nowhere higher to go.
• UK peat bogs dry out in hotter summers, releasing more CO₂ (feedback loop).

3. Extinction risk. Species that cannot migrate or adapt fast enough face extinction. Especially at risk:

• Specialised species (one food source, one habitat).
• Slow-reproducing species (large mammals).
• Species at climate range edges (mountaintops, islands). The IPCC estimates 1 in 6 species worldwide is at high extinction risk if warming continues to 4°C.

4. Rising sea levels. Sea level rises through TWO mechanisms:

• Thermal expansion — warm water occupies more volume.
• Melting ice — land-based ice (Greenland, Antarctica, mountain glaciers) adds new water to oceans. (Sea ice melting does NOT raise sea level — it was already floating.)

Sea level has risen ~25 cm since 1900 and is accelerating. Projected rise this century: 30–100 cm.

UK coastal flooding risk — low-lying areas like the Norfolk Broads, parts of London (Thames Estuary), Cornwall and the Fens are at increasing risk. The Thames Barrier was closed 200+ times since 1983 — far more often than originally planned.

Evidence that warming is real and human-caused:

1. Direct temperature records — thermometers from ~1850 show a clear upward trend.
2. CO₂ measurements — Mauna Loa observatory in Hawaii has measured atmospheric CO₂ since 1958; the curve goes only upward.
3. Ice cores — bubbles of ancient air in Antarctic ice show CO₂ levels for the past 800,000 years; current levels are way above any natural range.
4. Ocean temperatures — sea-surface temperatures rising; coral reefs bleaching.
5. Ice loss — satellites show Arctic sea ice, Greenland and Antarctic ice all shrinking.
6. Biological indicators — earlier spring, later autumn, shifting ranges all match warming patterns.

The scientific consensus. Over 97% of climate scientists agree that recent warming is caused by human emissions. This is one of the strongest consensuses in science.

Actions to reduce warming.

• Cut CO₂: renewable energy (wind, solar, nuclear), electric vehicles, energy efficiency, end deforestation.
• Cut methane: less beef and dairy, capture landfill methane, fix gas leaks.
• Protect carbon sinks: forests, peat bogs, oceans.
• Adapt: build flood defences, drought-resistant crops, plan species corridors.

UK targets. The UK aims for net-zero CO₂ emissions by 2050 (Climate Change Act 2008, amended 2019). Progress so far: emissions down ~50% since 1990, mainly by closing coal power stations.

Why evaluation matters in AQA exams. You may be asked whether sources for or against global warming are reliable. Use the criteria:

• Is it peer-reviewed?
• Who funded the research?
• Is the dataset long enough?
• Does it agree with other independent evidence?

Biodiversity is the variety of all living organisms in an ecosystem (or on the whole planet). It includes:

• The number of different species.
• The genetic variation within each species.
• The variety of different ecosystems.

Why high biodiversity is good:

1. Ecosystem stability. When many species fill many roles, the ecosystem doesn't collapse if one species struggles. A monoculture (single species) is fragile — one disease can wipe it out. A diverse forest is far more resilient.

2. Food security. Around three-quarters of the world's food crops depend on insect pollinators (bees, hoverflies, butterflies). Without diverse pollinator populations, food production collapses. Wild plants also provide a genetic library for breeding new crops.

3. Medicines. Around 50% of modern pharmaceutical drugs come from natural products discovered in wild species. Aspirin comes from willow bark. The cancer drug Taxol comes from yew trees. Lose the species → lose the discovery.

4. Ecosystem services. Wild ecosystems provide free services humans rely on: pollination, clean water filtration, flood prevention, soil formation, CO₂ removal. Estimated value: $125+ trillion per year globally.

5. Cultural and aesthetic value. Wildlife enriches life — think of UK favourites like otters returning to rivers, red kites soaring over Oxfordshire, puffins on the Farne Islands.

Threats to biodiversity (revision of earlier topics):

• Habitat destruction (building, farming, quarrying).
• Deforestation.
• Pollution (air, water, plastic).
• Climate change / global warming.
• Overhunting / overfishing.
• Invasive species (e.g. UK grey squirrels displacing red).

1. Breeding programmes for endangered species. Zoos, wildlife trusts and aquaria breed endangered species in captivity, then aim to reintroduce offspring to the wild. UK examples:

• Red kites — extinct in England by 1870, reintroduced from Spain/Sweden in the 1980s, now thriving in Oxfordshire and Wales.
• Beavers — reintroduced to Scotland (River Tay, 2009) and Devon (River Otter, 2014).
• Cirl bunting — bred and released back into Cornish farmland.

International examples: giant pandas (China), Arabian oryx (Middle East), California condor.

2. Protection of habitats and rare species. Nature reserves legally protect important habitats. Examples:

• UK: 224 National Nature Reserves, hundreds of Sites of Special Scientific Interest (SSSIs).
• Global: National parks, marine reserves (e.g. Great Barrier Reef Marine Park).
• International: CITES treaty bans trade in endangered species (ivory, tiger parts).

3. Regeneration of damaged habitats. Replanting forests, restoring peat bogs, rebuilding coral reefs, re-flooding drained wetlands. The 'rewilding' movement (e.g. Knepp Estate in Sussex) allows farmland to return to wild scrub and woodland — bringing back nightingales, turtle doves and white storks.

4. Reduction of deforestation and CO₂ emissions. Linked to topics 4.7.3.4 and 4.7.3.5. Cutting forest clearance and switching to renewable energy slow climate change — which protects species and habitats globally.

5. Recycling waste. Recycling reduces:

• Landfill (saves habitat from being used as dumps).
• Demand for raw materials (less quarrying and forestry).
• CO₂ emissions from making new materials. UK household recycling rate: ~44% — government target is 65% by 2035.

6. Hedgerow planting and field margins. On UK farms, hedgerows between fields and uncultivated field margins (strips of wildflower meadow) provide:

• Nest sites for birds and insects.
• Pollinator habitat (bees, butterflies).
• Wildlife corridors linking habitats.
• Natural pest control (predators eat crop pests). Government schemes (Countryside Stewardship, Sustainable Farming Incentive) pay farmers to maintain these features.

Conservation isn't free. Real-world programmes involve trade-offs that AQA wants you to discuss.

Example: nature reserves vs farming.

• For: protects species, supports tourism, climate benefits.
• Against: removes land from food production, farmers lose income unless compensated.

Example: reintroducing predators (lynx, wolves).

• For: restores natural balance, controls deer overpopulation, ecotourism income.
• Against: farmers fear livestock losses, some communities oppose, requires fencing/compensation.

Example: peat-free compost requirement.

• For: protects peatlands, reduces CO₂ emissions.
• Against: alternatives can be more expensive, peat industry jobs lost.

Example: hedgerow and field-margin payments.

• For: biodiversity boost, pollinators help adjacent crops.
• Against: less land for crops, government subsidies cost taxpayers.

How to write an evaluation answer:

1. State the conservation aim (e.g. 'protect peatlands').
2. Give a benefit (biodiversity, CO₂, etc.).
3. Give a drawback (cost, lost jobs, lost food production).
4. Conclude with a reasoned judgement.

The bigger picture. Many drawbacks are short-term and local; many benefits are long-term and global. AQA examiners reward answers that weigh both timescales.