Environmental Change

Look around you. Roads, buildings, farms and factories were all built by people. To make them, humans have changed the natural environment on a huge scale.

Some of these changes are helpful, but many cause problems for other living things. The environment is everything around an organism — the air, water, soil and other species it shares space with. When we change one part of it, the effects spread.

Three big ways humans change the environment are:

• Pollution — adding harmful substances to air, water or land.
• Deforestation — clearing forests for farmland, roads or building.
• Releasing greenhouse gases — burning fuels that warm the planet.

A useful idea here is the habitat — the place where a particular species lives. When we change or destroy a habitat, the species that depend on it lose their home, their food and their shelter. Throughout this topic, keep asking: who else lives here, and how does this change affect them?

Pollution means releasing harmful substances — called pollutants — into the environment. It happens in three places.

• Air pollution — gases and smoke from burning fuels in cars and factories. It can cause breathing problems and acid rain.
• Water pollution — waste, chemicals or fertilisers washing into rivers and seas. It can poison fish and other water life.
• Land pollution — rubbish, plastics and chemicals dumped on the ground. It can harm soil and the animals that live in it.

The key idea: a pollutant is harmful to living things, not just untidy. Many pollutants spread far from where they started.

Earth is warm enough for life because of the greenhouse effect. Certain gases in the atmosphere act like the glass of a greenhouse: they let sunlight in, but trap some of the heat that the warm Earth gives off.

A natural greenhouse effect is a good thing — without it, Earth would be far too cold.

The problem is that human activities add extra greenhouse gases to the atmosphere:

• Carbon dioxide — released when we burn fuels such as coal, oil and gas.
• Methane — released from farming and from waste.

More greenhouse gas means more heat trapped, so average temperatures rise. This is called global warming, and it drives wider climate change — shifting weather patterns, melting ice and rising sea levels.

Deforestation is the clearing of forests on a large scale — usually to make space for farmland, roads, mining or building.

Forests are some of the richest habitats on Earth. When a forest is cleared, the animals and plants that lived there lose their home, their food and their shelter all at once. This is habitat loss, and it is one of the biggest threats to wildlife.

Deforestation causes harm in several ways:

• Habitat loss — countless species are left with nowhere to live.
• Less photosynthesis — fewer trees means less carbon dioxide is removed from the air.
• More carbon dioxide — burning the cleared trees releases even more of it.
• Soil erosion — without tree roots to hold it, soil is washed or blown away.

So deforestation links straight back to the greenhouse effect: it both removes the trees that absorb carbon dioxide and releases more of the gas. Protecting forests protects habitats and helps slow climate change.

Biodiversity means the variety of different living things found in an area — how many different species there are.

A natural rainforest has high biodiversity — thousands of species share it. A field growing one crop has low biodiversity — almost everything in it is the same.

High biodiversity matters because:

• It makes an ecosystem more stable — if one species struggles, others can fill the gap.
• It supports more food chains and food webs.
• It gives humans useful things — foods, materials and medicines.

When habitats are destroyed or polluted, biodiversity falls, and the whole ecosystem becomes more fragile.

When the last member of a species dies, that species becomes extinct — gone forever. Extinction cannot be undone, so it matters greatly.

Conservation is the work of protecting species and habitats so they survive into the future. A species at high risk of extinction is described as endangered.

People conserve wildlife in many ways:

• Protected areas — national parks and nature reserves where habitats are kept safe.
• Laws — rules that ban hunting endangered animals or cutting protected forests.
• Captive breeding — raising endangered animals in zoos, then releasing them into the wild.
• Replanting — planting new trees to replace those lost to deforestation.
• Reducing pollution — cleaning up air, water and land so habitats stay healthy.

You can help too: recycling, saving energy and using less plastic all reduce the pressure on the environment. Small actions, multiplied by many people, make a real difference.

Understanding environmental change connects to many topics ahead:

• Ecosystems and food webs — losing one species through pollution or habitat loss affects every species linked to it.
• The carbon cycle — photosynthesis, respiration and burning fuels all move carbon between living things and the air.
• Adaptation — species that cannot adapt fast enough to a changing environment are most at risk.
• Citizenship and choices — the science here informs real decisions about energy, transport and recycling.

This topic is not just facts to learn — it is about the world you will live in and shape. Take it seriously, and remember that understanding a problem is the first step to solving it.