Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want human influences on ecosystems — pollution, habitat destruction and conservation — to become reliable marks instead of generic “humans damage the environment” answers.
What query it owns: how to understand and revise human influences on ecosystems in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the human-influences-on-ecosystems revision-guide angle, while Tutopiya’s Human Influences on Ecosystems subtopic page owns the learning resource and the free Human Influences on Ecosystems quiz owns the practice.

Human activities significantly affect ecosystems through pollution, habitat destruction, overexploitation of resources and introduction of non-native species. Cambridge IGCSE Coordinated Science (0654) tests air and water pollution (including eutrophication), greenhouse gases, pesticides, deforestation and conservation strategies. This guide covers the syllabus examples, causal chains examiners reward, and the question types that appear every year.

Key takeaways

• Air pollution includes sulfur dioxide and oxides of nitrogen — linked to acid rain and respiratory disease.
• Greenhouse gases (e.g. carbon dioxide, methane) trap heat and contribute to climate change.
• Water pollution from sewage and fertilisers causes eutrophication — algal bloom → oxygen depletion → fish death.
• Habitat destruction (deforestation, urbanisation) reduces biodiversity and disrupts food webs.
• Conservation methods include protected areas, captive breeding, seed banks and sustainable resource use.

What are human influences on ecosystems in Cambridge IGCSE Coordinated Science?

Human influences on ecosystems are the ways human activities alter natural communities — adding pollutants, clearing habitats, overfishing, using pesticides and changing land use. The syllabus requires you to describe specific pollutants, how they enter ecosystems, their biological effects, and measures to reduce harm or protect species.

Read the full notes on Tutopiya’s Human Influences on Ecosystems subtopic page before attempting questions.

The core ideas you must master

Human influence	Source	Biological effect
Acid rain	SO₂, NOₓ from fossil fuels	Damages leaves, acidifies lakes, kills fish
Greenhouse effect	CO₂, methane	Climate change, habitat disruption
Eutrophication	Fertilisers, sewage in water	Algal bloom, deoxygenation, fish death
Pesticides	Agriculture	Bioaccumulation, harm food chains
Deforestation	Logging, farming	Habitat loss, reduced biodiversity

Eutrophication — step by step

1. Excess nitrate/phosphate enters water from fertiliser or sewage.
2. Rapid algal growth (algal bloom) on the surface.
3. Light blocked from submerged plants, which die.
4. Aerobic bacteria decompose dead matter, using dissolved oxygen.
5. Oxygen depletion kills fish and aquatic invertebrates.

Conservation strategies

Strategy	What it involves	Example
Protected areas	Legally safeguard habitats	National parks, marine reserves
Captive breeding	Breed endangered species in captivity	Release to wild when safe
Seed banks	Store seeds of rare plants	Kew Millennium Seed Bank
Sustainable fishing	Limits on catch size and season	Quotas, net mesh size rules
Reforestation	Plant trees to replace lost forest	Afforestation programmes

Human influences in past-paper wording

Command word	What the question wants	Typical stem
Define	Precise definition	”Define eutrophication.”
Describe	Sequence of events	”Describe how fertiliser runoff affects a lake.”
Explain	Cause and effect	”Explain how acid rain affects trees.”
Suggest	Apply to scenario	”Suggest how to reduce water pollution.”
State	Short fact	”State one source of atmospheric carbon dioxide.”

Worked exam-style stems

1. “Describe the process of eutrophication.” Excess nitrates/phosphates enter water → algal bloom → light blocked → submerged plants die → bacteria decompose dead material using oxygen → oxygen levels fall → fish die. Reward: ordered steps with oxygen depletion.
2. “Explain how sulfur dioxide causes acid rain.” SO₂ dissolves in rainwater forming sulfuric acid; acid rain lowers pH of lakes and damages plant leaves. Reward: gas → acid → biological effect.
3. “Suggest two ways humans can reduce their impact on ecosystems.” Any two from: treat sewage, reduce fertiliser use, protect habitats, use sustainable fishing, reduce fossil fuel burning. Reward: practical, syllabus-linked measures.

Practise on the Human Influences on Ecosystems quiz.

How human influences connect to the syllabus

Human influences link to Organisms and Their Environment (food webs disrupted by pollution) and Variation and Selection (selection pressures from environmental change). The Cambridge IGCSE Coordinated Science resource hub links every ecology subtopic.

Common mistakes students make

• Describing eutrophication without oxygen depletion and fish death.
• Confusing greenhouse effect with ozone depletion.
• Saying pollution always kills all organisms without naming the chain of events.
• Omitting named pollutants (SO₂, nitrates, pesticides) in explain answers.
• Ignoring bioaccumulation of pesticides in food chains.

When you need more support

If pollution and conservation questions keep costing marks, work through the Human Influences on Ecosystems quiz, then get help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

What is eutrophication? Excess nutrients in water cause algal blooms, oxygen depletion and death of aquatic organisms.

How does deforestation affect ecosystems? It destroys habitats, reduces biodiversity and can increase atmospheric carbon dioxide.

What are greenhouse gases? Gases such as carbon dioxide and methane that trap heat in the atmosphere, contributing to climate change.

How do I revise human influences on ecosystems effectively? Learn eutrophication steps, named pollutants, conservation methods, then take the quiz.

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