Human Impacts on Biodiversity

HSC Biology | Free Study Notes

In this lesson

• how habitat destruction affects biodiversity

• how introduced species affect ecosystems

• how pollution reduces biodiversity

• what conservation means

• why protecting biodiversity matters

Why human impacts matter

Biodiversity depends on the variety of:

• genes

• species

• ecosystems

Human activity can reduce this variety by:

• destroying habitats

• changing food webs

• reducing population sizes

• lowering genetic diversity

• causing species decline or extinction

This means human actions can affect biodiversity at more than one level.

Habitat destruction

Habitat destruction is the removal or severe alteration of the natural environment where organisms live.

Examples of habitat destruction

• land clearing

• deforestation

• urban development

• mining

• draining wetlands

• agricultural expansion

Why habitat destruction reduces biodiversity

Habitat destruction can:

• remove food sources

• remove shelter and breeding sites

• split populations into smaller isolated groups

• increase competition for the remaining resources

Effects on biodiversity

When habitats are destroyed:

• some species may disappear from the area

• species richness may decrease

• abundance of some populations may fall

• genetic diversity may decline if populations become very small

Important idea

A species may not survive even if a few individuals remain, because a damaged habitat may no longer provide the conditions needed for reproduction and long-term survival.

Introduced species

An introduced species is a species moved by humans, deliberately or accidentally, into an area where it does not naturally occur.

Why introduced species can be a problem

Introduced species may:

• compete with native species for food and shelter

• prey on native species

• spread disease

• reproduce quickly

• disrupt food webs

Why this affects biodiversity

If introduced species outcompete or reduce native populations, then native biodiversity may decline.

Important idea

Introduced species are not always harmful, but they can become serious threats when they have no natural predators or controls in the new environment.

Pollution

Pollution is the release of harmful substances or energy into the environment.

Examples of pollution

• chemical pollution in water

• plastic pollution

• oil spills

• air pollution

• pesticide runoff

• excess nutrients entering waterways

Why pollution reduces biodiversity

Pollution can:

• poison organisms

• reduce reproductive success

• damage habitats

• alter food chains

• lower water or soil quality

Example effects

• aquatic organisms may die if water quality falls

• plants may be damaged by soil contamination

• animals may ingest plastics or toxins

• sensitive species may disappear first, lowering species diversity

Conservation

Conservation is the protection and management of biodiversity, species and ecosystems.

Why conservation matters

Conservation aims to:

• protect habitats

• maintain populations

• prevent extinction

• preserve genetic diversity

• restore damaged ecosystems

Examples of conservation strategies

• national parks and protected areas

• habitat restoration

• control of introduced species

• pollution reduction

• captive breeding programs

• laws that protect threatened species

Key idea

Conservation is not just about saving one species. It is about protecting ecosystems and

maintaining biodiversity over time.

How these impacts connect

Human impacts often work together rather than separately.

Example

A habitat may be cleared, then polluted, then invaded by introduced species.

This can cause:

• rapid decline in native populations

• reduced genetic diversity

• lower species richness

• disruption of ecosystem stability

So biodiversity loss is often caused by several pressures acting at once.

Human impacts and long-term ecosystem change

When biodiversity is reduced:

• food webs may become less stable

• populations may be more vulnerable to disease or environmental change

• ecosystems may lose resilience

This is why biodiversity protection is important not only for individual species, but for the long-term health of whole ecosystems.

Worked example

Exam-style question

Explain how one human activity can reduce biodiversity.

Worked answer

Habitat destruction can reduce biodiversity because it removes the environment that organisms need for food, shelter and reproduction. This can lower population size, reduce species richness, and cause some species to disappear from the area.

Why this works

This answer:

• identifies one human activity

• explains the mechanism clearly

• links the impact directly to biodiversity

Common mistakes

• Saying biodiversity loss only means extinction.

• Treating introduced species as harmful in every case without explanation.

• Describing pollution generally without linking it to species or ecosystems.

• Confusing conservation with preservation of just one animal.

• Forgetting that habitat destruction can also reduce genetic diversity by isolating populations.

Quick quiz

1. What is habitat destruction?

2. How can introduced species reduce biodiversity?

3. Give one example of pollution that can damage ecosystems.

4. What does conservation mean?

5. Why can habitat destruction reduce genetic diversity as well as species diversity?

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