Key Stage 3 geography · Human and physical interactions

KS3 geography: how people depend on natural systems

People often think of nature as a backdrop to human life, but Key Stage 3 geography teaches the opposite: our food, water, climate and safety rely on natural systems working properly. Students learn to describe natural systems, such as the water cycle, the carbon cycle and ecosystems, and to explain what happens to the people who depend on them when those systems are damaged. It builds the systems thinking that later GCSE geography and science rely on.

How people depend on natural systems, explained

A system is a set of connected parts. In a natural system, geographers describe inputs (what goes in), stores (where things are held), transfers or flows (how things move between stores) and outputs (what leaves). The water cycle in a drainage basin, the area of land drained by a river, is the classic example: rain and snow are the inputs; plants, soil, groundwater and lakes are stores; infiltration and run-off are transfers; and evaporation, transpiration from plants and the river’s flow into the sea are outputs. At the scale of the whole planet, the water cycle is a closed system, with the same water moving between oceans, air and land. Students learn to draw and label these and then ask what happens if one part is changed.

The benefits that people receive from natural systems are called ecosystem services. Some are provisioning services, which provide things we take directly, such as food, fresh water, timber and fuel. Others are regulating services, such as trees and wetlands that soak up floodwater, bees and other insects that pollinate crops, and plants and oceans that take in carbon dioxide and help to regulate climate. Supporting services, such as soil formation and the cycling of nutrients, underpin all the rest. Cultural services include the enjoyment people get from beautiful places.

The key idea is dependence. Farming needs fertile soil, rain and pollinators. Cities need clean water that has often been collected and filtered by upland land and rivers. Coastal towns are protected from storms by dunes, marshes or mangrove forests, if these are healthy. Students can see that the economy sits inside the environment, not outside it, and that damaging a natural system can create costs that fall on people, often far away or years later.

Natural systems are also complex. A change in one part may have effects that are surprising or delayed, and some systems can only take so much damage before they change completely, a point sometimes called a tipping point. Students look at feedback as well. In a negative feedback, a change triggers a response that reduces it; in a positive feedback, the change makes itself bigger. Schools choose their own examples here; some use melting Arctic ice, where less bright ice means more heat is absorbed and more ice melts, a positive feedback.

This topic links closely to the use of natural resources and to how human and physical processes change landscapes and climate, but its focus is different: it asks what we get from nature and what happens if it stops working. The statutory wording is brief, so schools differ in the examples they pick, which could include a wetland, a coral reef, a farming region or a national park. Ask your teenager which place-based examples they have used, and whether the unit ended with a decision-making task about how to protect a system.

Words your child will hear

System: A set of connected parts, with inputs, stores, transfers and outputs.
Ecosystem: A community of living things and the physical environment in which they live and interact.
Ecosystem service: A benefit that people get from nature, such as clean water, pollination or flood protection.
Biodiversity: The variety of living things in a place, from plants and insects to larger animals.
Carbon cycle: The movement of carbon between the air, living things, soil, rocks and oceans.
Feedback: A process in which a change either reinforces itself (positive) or is damped down (negative).
Tipping point: A threshold beyond which a system changes quickly and may not return to how it was.

What the National Curriculum says

The programme of study for Key Stage 3 says:

Pupils should be taught to understand how human and physical processes interact to influence and change landscapes, environments and the climate; and how human activity relies on the effective functioning of natural systems
Pupils should become aware of increasingly complex geographical systems in the world around them.

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

A model answer: explaining a dependence

Many people in towns and cities get drinking water that falls as rain on upland moors with peat bogs. Explain how the health of the bog affects the people who depend on it.

Name the system and its services. A healthy peat bog is waterlogged ground full of partly decayed plants. It stores rainwater, filters it as it passes through and releases it slowly into streams and reservoirs. It also stores large amounts of carbon in the peat, which helps regulate climate.
Describe what happens when the system is damaged. If a bog is drained for farming or grazing, or burnt, or eroded, the peat dries out. Dry peat breaks down and releases carbon dioxide. Rain no longer soaks in, so it rushes off the surface more quickly, and the peat washes into streams and gives the water a brown colour.
Link to people. Brown, peat-rich water costs more to clean, which can raise bills. Faster run-off can raise flood risk in valleys downstream. Release of stored carbon adds to climate change, which affects everyone.
Show how people can respond. Blocking old drainage ditches re-wets the bog, replanting bare peat with bog plants such as sphagnum moss helps to hold it in place, and some water companies fund this kind of restoration on the land their water comes from. The costs are weighed against cheaper, cleaner water, lower flood risk and carbon kept in the ground.

People depend on a healthy peat bog for clean water, steady river flow and carbon storage. If the bog is drained or damaged, water becomes dirtier and more expensive to treat, floods may become more likely downstream and stored carbon is released as carbon dioxide. Restoring the bog costs money, but protects services that are hard and expensive to replace by other means.

Common mistakes and how to help

Thinking that nature and the economy are separate

Factories, shops and screens feel like “the economy”, while forests and rivers feel like “the environment”.

What helps: Trace an everyday item, a glass of water or a sandwich, back to its natural inputs. Everything economic starts with soil, water, air or sunlight.

Believing a damaged system will recover on its own, quickly

Gardens regrow and rivers refill, so nature seems endlessly resilient.

What helps: Some systems recover slowly or not at all once a tipping point is passed. Peat, for example, builds up over thousands of years, so a damaged bog cannot be replaced within a lifetime.

Writing about nature’s benefits only as money or resources

Resources are the easiest to name, so regulating and cultural services get missed.

What helps: Use the four types of ecosystem service as a checklist: provisioning, regulating, supporting and cultural. Ask which of them a place offers.

Treating a feedback as a one-off cause and effect

Chains of the “A causes B” type are easier to draw and remember than loops.

What helps: Draw a loop that returns to its starting point. Ask whether the change at the end makes the start bigger (positive feedback) or smaller (negative feedback).

How to help at home

Map a system in the garden or park. Choose a small area, such as a hedge, a tree or a flower bed, and sketch what goes in, what is stored and what leaves. Ask what would happen if one part was removed.
Notice the services around you. On a walk, name every benefit nature is providing, from shade and shelter to blossom for insects and a river carrying away rain. Sort them into provisioning, regulating, supporting and cultural.
Follow your drinking water. Find out, perhaps from your water supplier’s leaflets or a sign at a local reservoir, where your tap water comes from. Talk about what the land around it does for the water.
Grow something and track its needs. Sow cress or salad leaves on a windowsill, keep a note of what they need and what happens if one thing is left out. It makes dependence concrete in a safe, cheap way.
Discuss a trade-off in the news. When a story involves building on green space or draining wetlands, ask which natural services would be lost and which human needs the project would meet. Look for a decision that gives both some weight.

Builds on

Key Stage 2: Climate zones, biomes and vegetation belts
Key Stage 2: Rivers and the water cycle
Key Stage 2: Mountains
Key Stage 2: Volcanoes and earthquakes
Key Stage 2: Settlements and land use
Key Stage 2: Economic activity and trade
Key Stage 2: Natural resources