How do human activities pollute and damage the environment, and what can reduce that impact?
Describe the effects of human activity on the environment including pollution, the enhanced greenhouse effect and deforestation, and outline ways to reduce the impact
A focused answer to the O-Level Combined Science outcome on human impact. Air and water pollution, the enhanced greenhouse effect and global warming, acid rain, deforestation and its effects, and measures to reduce environmental damage.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
SEAB wants you to describe the harmful effects of human activity on the environment - pollution of air and water, the enhanced greenhouse effect and global warming, acid rain and deforestation - and to outline measures that reduce the impact. Clear cause-and-effect explanations and sensible solutions are the marks here.
The answer
Air pollution
Burning fossil fuels and other activities release harmful gases:
- carbon dioxide: a greenhouse gas that adds to global warming,
- sulfur dioxide and nitrogen oxides: cause acid rain,
- carbon monoxide: a poisonous gas from incomplete combustion.
The enhanced greenhouse effect and global warming
Greenhouse gases such as carbon dioxide and methane trap heat that would otherwise escape from the Earth into space. Human activity, especially burning fossil fuels, has raised their concentration, trapping more heat. This enhanced greenhouse effect causes global warming, which can lead to melting ice, rising sea levels, flooding, changed weather patterns, and loss of habitats and species.
Acid rain
Sulfur dioxide and nitrogen oxides dissolve in rainwater to form acids. Acid rain damages trees, makes lakes too acidic for fish, and erodes limestone buildings and statues. Using cleaner fuels and removing sulfur from fuels reduces it.
Water pollution
Pollutants reach rivers and seas in several ways:
- fertilisers washed from fields cause eutrophication (excess nutrients make algae grow, then decay, using up oxygen and killing fish),
- sewage and industrial waste poison water and use up oxygen as they decay,
- oil spills harm sea birds and marine life.
Deforestation
Cutting down large areas of forest:
- increases carbon dioxide (less photosynthesis to remove it, and burning trees releases stored carbon),
- destroys habitats, reducing biodiversity,
- causes soil erosion and flooding, because roots no longer hold the soil.
Reducing the impact
Measures to reduce environmental damage include:
- using renewable energy and burning less fossil fuel (less carbon dioxide),
- recycling materials to save resources and energy,
- treating sewage and waste before release,
- replanting trees (reforestation) and conserving habitats,
- fitting catalytic converters and removing sulfur from fuels.
Examples in context
Example 1. Eutrophication of a farm pond. When fertiliser washes into a pond, algae grow rapidly into a bloom, then die and are decomposed by bacteria that use up the dissolved oxygen, so fish suffocate. This shows how a useful farming chemical can damage a nearby ecosystem.
Example 2. International action on emissions. Many countries have agreed to cut greenhouse gas emissions and switch to renewable energy to slow global warming. This reflects the understanding that reducing carbon dioxide from fossil fuels is the key step in limiting the enhanced greenhouse effect.
Try this
Q1. Name two gases released by burning fossil fuels and state the environmental problem each causes. [2 marks]
- Cue. Carbon dioxide causes global warming (the enhanced greenhouse effect); sulfur dioxide causes acid rain.
Q2. Explain how deforestation increases the amount of carbon dioxide in the atmosphere. [2 marks]
- Cue. Fewer trees means less photosynthesis to remove carbon dioxide, and burning the felled trees releases stored carbon as carbon dioxide.
Q3. Suggest two ways of reducing the impact of human activity on the environment. [2 marks]
- Cue. Any two of: use renewable energy / burn less fossil fuel, recycle materials, treat sewage and waste, replant trees, fit catalytic converters.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original4 marksExplain how the burning of fossil fuels contributes to the enhanced greenhouse effect and global warming, and state two consequences of global warming.Show worked answer →
Burning fossil fuels releases carbon dioxide, a greenhouse gas, into the atmosphere. The greenhouse gases absorb and trap heat (long-wave radiation) that would otherwise escape from the Earth into space. As the concentration of carbon dioxide rises, more heat is trapped, so the average temperature of the Earth increases. This is the enhanced greenhouse effect, which causes global warming.
Two consequences (any two): melting of polar ice and glaciers raising sea levels (and flooding of low-lying land); more extreme or changed weather patterns; loss of habitats and species; changes to where crops can be grown.
Markers reward carbon dioxide from burning fossil fuels acting as a greenhouse gas that traps heat, the rise in average temperature, and two valid consequences such as rising sea levels and changed weather.
Original4 marksDeforestation is the large-scale removal of forests. Explain two ways in which deforestation harms the environment.Show worked answer →
Way 1: deforestation increases the amount of carbon dioxide in the atmosphere. Fewer trees means less photosynthesis to remove carbon dioxide, and burning the felled trees releases stored carbon. This adds to the greenhouse effect and global warming.
Way 2: deforestation destroys habitats, reducing biodiversity (loss of species). It also leads to soil erosion, because tree roots no longer hold the soil together and rain washes it away (and can cause flooding).
Markers reward two correct harmful effects, each explained, for example more carbon dioxide (less photosynthesis plus burning) adding to warming, and loss of habitat/biodiversity or soil erosion.
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