What you'll learn
An ecosystem is a community of plants and animals interacting with each other and with their physical environment. This guide covers what you need for Edexcel GCSE Geography on ecosystems, biodiversity and management: the distribution of global ecosystems and the climate that controls it, how ecosystems provide goods and services, the main UK ecosystems, the characteristics of tropical rainforests and coral reefs, how plants and animals have adapted to them, the threats these ecosystems face, and how they can be managed sustainably. The Amazon rainforest is used as the main example.
Questions ask you to describe the distribution of ecosystems from a map, explain how climate influences them, explain adaptations, and evaluate the causes of and solutions to ecosystem loss. Use specific examples and link features to explanations.
Key terms and definitions
Ecosystem — A community of living things interacting with each other and their non-living environment.
Biome — A large-scale ecosystem covering a wide area, such as tropical rainforest or desert.
Biodiversity — The variety of plant and animal life in an area.
Biotic — Living parts of an ecosystem, such as plants and animals.
Abiotic — Non-living parts, such as climate, soil and water.
Nutrient cycle — The movement of nutrients between living things, the soil and the litter layer.
Adaptation — A feature that helps a plant or animal survive in its environment.
Deforestation — The cutting down and removal of forest.
Goods and services — The products (such as food and timber) and benefits (such as climate regulation) that ecosystems provide to people.
Sustainable management — Using an ecosystem in a way that meets present needs without harming its ability to meet future needs.
Coral bleaching — Corals expelling the algae living in them, usually due to raised water temperatures, turning white and often dying.
Core concepts
Global distribution of ecosystems
Climate — particularly temperature and rainfall — is the main factor controlling where biomes are found, and it is linked to the global atmospheric circulation:
- Tropical rainforests lie near the equator, where rising air brings high rainfall and the Sun is strong all year.
- Hot deserts lie around 30° north and south, where sinking air creates high pressure and very little rain.
- Temperate deciduous forests are found in mid-latitudes, such as the UK, with mild temperatures and rain all year.
- Tundra lies near the poles, with very cold temperatures and a short growing season.
- Coral reefs are found in warm, shallow, clear tropical seas.
Other factors include altitude (it gets colder with height), soil type, distance from the sea and ocean currents.
Goods and services
Ecosystems provide goods such as food, fresh water, timber, fuel, medicines and building materials, and services such as regulating the climate by storing carbon, producing oxygen, purifying water, preventing soil erosion and flooding, pollinating crops, and providing places for recreation and tourism. Healthy ecosystems are therefore vital for human wellbeing.
UK ecosystems
The UK has a range of ecosystems, including moorlands, heathlands, woodlands, wetlands and marine ecosystems. Moorlands store large amounts of carbon in peat and supply drinking water; woodlands provide timber and recreation; wetlands reduce flooding and support birds; marine ecosystems support fishing. Threats include overgrazing, draining of wetlands, development, pollution, overfishing and climate change. Management includes protected areas such as National Parks and Sites of Special Scientific Interest, peat restoration and sustainable fishing quotas.
Tropical rainforests
Climate: hot all year (around 27°C) with very little seasonal variation, and very high rainfall (often above 2,000 mm a year), with heavy afternoon convectional storms.
Structure (layers):
- Emergents — the tallest trees, reaching up to around 50 m, rising above the canopy.
- Canopy — a dense layer of tree tops that absorbs most sunlight and holds most wildlife.
- Understorey — younger trees and shrubs in low light.
- Forest floor — dark and damp, covered in leaf litter.
Nutrient cycle: nutrients are stored mainly in the biomass (living plants), not the soil. Leaves fall and decompose quickly in the hot, wet conditions; nutrients are rapidly taken up again by plant roots. Soils are therefore thin and nutrient-poor, so when the forest is cleared, nutrients are quickly washed away (leaching) and the land becomes infertile.
Adaptations:
- Buttress roots support tall trees in shallow soils.
- Drip tips on leaves let heavy rain run off, preventing rot.
- Lianas (woody vines) climb trees to reach sunlight.
- Epiphytes grow on other plants to reach light in the canopy.
- Animals such as sloths are camouflaged and move slowly to save energy; many animals are adapted to life in the canopy, with grasping tails or the ability to glide.
Biodiversity: rainforests cover a small proportion of the Earth's land but contain over half of its plant and animal species.
Threats to the Amazon rainforest
The Amazon, mostly in Brazil, is the world's largest tropical rainforest. Causes of deforestation include:
- cattle ranching — the largest cause; land is cleared for grazing;
- commercial farming — especially soya;
- logging — legal and illegal timber extraction;
- mining — for gold, iron ore and other minerals;
- road building — such as the Trans-Amazonian Highway, opening up remote areas;
- hydroelectric power — dams flood large areas of forest;
- settlement — as populations grow.
Impacts include loss of biodiversity and species extinction; release of carbon dioxide, contributing to climate change; soil erosion and leaching; disruption of the water cycle, potentially reducing rainfall; and harm to indigenous peoples whose lands and ways of life are threatened. There are also economic benefits — jobs, exports and income for Brazil's economy — which explain why deforestation continues.
Coral reefs
Coral reefs grow in warm (around 18–29°C), shallow, clear, salty water where sunlight can reach the algae living within the coral. They have very high biodiversity, protect coasts from waves, support fisheries and attract tourists.
Threats include coral bleaching caused by rising sea temperatures, ocean acidification as the sea absorbs carbon dioxide, pollution and sediment from farming and development, overfishing and destructive fishing methods, and damage from tourism. The Great Barrier Reef in Australia has suffered several major bleaching events in recent years.
Sustainable management
Strategies for rainforests include:
- Protected areas and national parks, where development is restricted.
- Selective logging, removing only some mature trees so the forest can regenerate.
- Replanting (afforestation) after logging.
- Ecotourism, which brings income from visitors while protecting the forest and employing local people.
- Debt-for-nature swaps, where part of a country's debt is cancelled in return for conservation.
- International agreements and certification, such as labelling sustainably sourced timber.
- Monitoring using satellites to detect illegal clearance.
- Supporting indigenous land rights, since indigenous territories often have lower deforestation.
Strategies for coral reefs include marine protected areas, fishing restrictions, reducing pollution from land, controlling tourism and reducing global greenhouse gas emissions.
The challenge is balancing economic development, which brings jobs and income, with conservation, which protects the long-term benefits ecosystems provide to everyone.
A UK ecosystem in detail: moorland
Moorlands cover large upland areas of the UK, such as the Pennines, Dartmoor and the North York Moors. They have thin, acidic soils and blanket peat bogs, with vegetation such as heather, cotton grass and sphagnum moss.
Goods and services: peat stores very large amounts of carbon; moorlands supply much of the UK's drinking water from upland reservoirs; they support sheep farming and grouse shooting; and they attract walkers and tourists.
Threats: draining peat for farming dries it out, releasing carbon and increasing flood risk downstream; overgrazing damages vegetation; wildfires and controlled burning release carbon; footpath erosion is severe in popular areas; and climate change may dry peat further.
Management: blocking drainage ditches to re-wet peat, replanting sphagnum moss, reducing grazing, footpath repair and protecting areas as National Parks or Sites of Special Scientific Interest. Restored peat stores carbon again and slows the flow of water into rivers, reducing flood peaks.
The taiga
The taiga (boreal forest) stretches across northern Canada, Scandinavia and Russia. It has long, very cold winters and short, mild summers, and is dominated by coniferous trees such as spruce, pine and fir, whose needle-shaped leaves and conical shape help them cope with cold and snow. It stores huge amounts of carbon in its trees and soils. Threats include logging for timber and paper, mining, oil and gas extraction, and an increase in wildfires linked to climate change.
Worked examples
Example 1: Adaptations
Explain how two plant adaptations help plants survive in a tropical rainforest. (4 marks)
Answer: Drip tips on leaves (1) allow heavy rain to run off quickly, preventing the growth of fungi and algae (1). Buttress roots (1) provide support for very tall trees growing in shallow soils (1).
Example 2: Nutrient cycle
Explain why rainforest soils become infertile after deforestation. (3 marks)
Answer: Most nutrients are stored in the vegetation rather than the soil (1). When trees are removed, there is no new leaf litter to replace nutrients (1). Heavy rainfall washes the remaining nutrients out of the soil by leaching, so it becomes infertile (1).
Example 3: Evaluating management
Evaluate ecotourism as a way of protecting the rainforest.
Answer: Ecotourism provides income and jobs for local people, giving them a reason to protect the forest rather than clear it, and it can fund conservation. However, it only works in accessible areas, visitor numbers must be controlled to avoid damage, and flights to reach the forest add to greenhouse gas emissions. It is useful as part of a wider plan but cannot protect the whole Amazon on its own.
Common mistakes and how to avoid them
- Describing a distribution map without naming places or latitudes.
- Saying rainforest soils are fertile. They are poor because nutrients are stored in plants.
- Listing adaptations without explaining them.
- Ignoring the economic reasons for deforestation, which leads to one-sided answers.
- Confusing goods and services.
Exam technique for "Ecosystems, Biodiversity and Management"
- For distribution questions, use compass directions, latitudes and named continents or countries.
- Link climate to the global atmospheric circulation when explaining distribution.
- For causes and impacts, consider social, economic and environmental factors.
- In evaluations, weigh effectiveness, cost and who benefits, then reach a conclusion.
Quick revision summary
- Climate controls the distribution of biomes, linked to global atmospheric circulation.
- Ecosystems provide goods (food, timber, medicines) and services (carbon storage, water, flood control).
- UK ecosystems: moorland, heathland, woodland, wetland, marine.
- Rainforests: hot and wet all year; emergent, canopy, understorey, forest floor; nutrients stored in biomass; adaptations such as buttress roots, drip tips, lianas and epiphytes.
- Amazon threats: cattle ranching, soya, logging, mining, roads, dams; impacts on biodiversity, climate, soil and indigenous people.
- Coral reefs: warm, shallow, clear water; threatened by bleaching, acidification, pollution and overfishing.
- Sustainable management: protected areas, selective logging, ecotourism, debt-for-nature swaps, certification, monitoring and indigenous rights.