Human impact on the environment

Human activities have profoundly altered the natural environment at every scale — from local pollution to global climate change. CCEA examiners expect you to describe and evaluate impacts across local, regional and global scales.

Local scale impacts

Water pollution: agricultural runoff (nitrates and phosphates from fertilisers), sewage discharge, and industrial effluent contaminate rivers and lakes locally. In NI, agricultural runoff into Lough Neagh is a major issue — algal blooms caused by phosphorus enrichment (eutrophication) have plagued the lough. In 2023, a severe algal bloom covered much of Lough Neagh, threatening drinking water supplies for 40% of NI's population.

Air pollution: local traffic emissions (NOx, particulates) in urban areas. Belfast's air quality monitoring shows frequent exceedances of PM2.5 standards in the city centre and near busy roads.

Land degradation: overgrazing, intensive farming, and urban sprawl degrade soil quality and natural habitats locally. NI has lost over 90% of its ancient woodland over the past few centuries.

Noise and light pollution: affects local wildlife (disrupts bird navigation, insect cycles) and human health.

Regional scale impacts

Acid rain: sulphur dioxide (SO₂) and nitrogen oxides (NOx) from power stations and vehicle emissions react with water vapour to form sulphuric and nitric acids, which fall as acid rain hundreds of kilometres downwind.

• Kills fish and invertebrates in lakes (pH drops below 5.5).
• Damages forests (killed vast areas of Scandinavian and German forests in the 1970s-80s; improved by reducing SO₂ emissions through catalytic converters and cleaner power).
• Corrodes limestone buildings and statues.
• NI's Black Water River system and upland lakes are naturally sensitive to acidification.

Eutrophication (regional): nutrient enrichment from agricultural runoff can affect entire river systems and coastal bays (the Irish Sea receives significant agricultural runoff from NI and the Republic).

Deforestation (regional): large-scale clearing in the Amazon basin affects regional rainfall patterns (trees release moisture through transpiration — a "flying rivers" effect that drives inland rainfall).

Global scale impacts

Climate change: the dominant global environmental impact. CO₂ and methane from burning fossil fuels and agriculture are altering the global energy balance, causing warming, sea level rise, and increasingly extreme weather. (See U1.WC.3 for detail.)

Ozone depletion: CFCs (chlorofluorocarbons) from aerosols and refrigerants depleted the stratospheric ozone layer, increasing UV radiation reaching Earth's surface. The 1987 Montreal Protocol successfully phased out CFCs — the ozone hole over Antarctica is slowly recovering. A major success story for international environmental cooperation.

Biodiversity loss (the "sixth mass extinction"): the current rate of species extinction is estimated at 100-1,000 times the natural background rate, driven by habitat destruction, invasive species, overexploitation, and climate change. Scientists estimate we are in the early stages of a sixth mass extinction.

Ocean acidification: CO₂ dissolves in seawater to form carbonic acid, lowering ocean pH. Ocean pH has fallen from 8.2 to 8.1 since industrialisation. Threatens coral reefs and shellfish (carbonate shells dissolve in acid water).

Plastic pollution: 8-10 million tonnes of plastic enter the ocean annually. The Great Pacific Garbage Patch (twice the area of Texas) is a visible symbol of global plastic pollution. Microplastics have been found in the deep ocean, Arctic ice, and human blood.