Human influences on ecosystems
Food production
Greenhouses and polythene tunnels raise crop yields by controlling limiting factors: higher temperature, extra CO₂ (from paraffin heaters) and artificial light. Fertilisers supply nitrate, phosphate and potassium. Pesticides kill pests but can harm other species and accumulate in food chains; biological control uses a natural predator instead. Fish farming keeps fish in controlled conditions with fed diets and disease control. Monocultures and intensive livestock increase output but reduce biodiversity and can spread disease and pollution.
≈ 35 minPollution and conservation
Humans destroy habitats for farming, building, mining and logging. Deforestation reduces biodiversity, increases CO₂ (less photosynthesis, burning), causes soil erosion and flooding. Eutrophication: fertilisers or sewage add nutrients → algal bloom → algae block light, plants die → decomposers respire and use up oxygen → fish die. Greenhouse gases (CO₂, methane) cause climate change. Plastics don't biodegrade and harm wildlife. Conservation protects species and habitats with reserves, laws, seed banks, captive breeding and education; sustainable use includes fishing quotas, net mesh sizes and replanting forests.
≈ 45 min