How do human activities affect biodiversity and the environment?
The effects of human activity on biodiversity, deforestation and agriculture, pollution and climate change, and conservation.
A focused answer to WJEC A-Level Biology Unit 3, covering the effects of human activity on biodiversity, deforestation and intensive agriculture, pollution including eutrophication, climate change, and conservation strategies.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
WJEC wants you to explain how human activities affect biodiversity, describe the impacts of deforestation and intensive agriculture, explain pollution including eutrophication and climate change, and describe conservation strategies and why they matter.
Effects on biodiversity
Deforestation removes habitats and food sources, fragments populations so they cannot interbreed, and reduces the number of producers, lowering the energy entering food webs. It also releases stored carbon and reduces the uptake of carbon dioxide, feeding into climate change.
Pollution and eutrophication
The key sequence to learn is: nutrients in, algal bloom, light blocked, plants die, bacteria decompose them, oxygen used up, fish suffocate. Note carefully that it is the decomposers, not the algae themselves, that remove the oxygen.
Climate change and conservation
Burning fossil fuels and deforestation increase carbon dioxide () and other greenhouse gases such as methane, enhancing the greenhouse effect and driving climate change, which shifts habitat ranges, alters rainfall and threatens species that cannot move or adapt fast enough.
Conservation protects biodiversity through protected areas and reserves, sustainable management (such as selective logging and replanting), seed banks that store genetic material, and captive breeding and reintroduction of threatened species. The aim is sustainable use: meeting human needs while preserving species, habitats and the genetic diversity future generations depend on.
Examples in context
Example 1. The Welsh peatlands. Restoring drained upland peat bogs in Wales locks away carbon and rebuilds habitat for specialist species. Drained peat oxidises and releases ; re-wetting reverses this. This is a real conservation strategy that tackles both biodiversity loss and climate change at once, a favourite local WJEC context.
Example 2. The Millennium Seed Bank. This facility stores seeds from tens of thousands of plant species as insurance against extinction. By preserving genetic diversity off-site, it allows species to be re-established after habitat loss, illustrating the seed-bank conservation method named in the specification.
Try this
Q1. Name one greenhouse gas released by burning fossil fuels. [1 mark]
- Cue. Carbon dioxide (or methane).
Q2. Explain why intensive monoculture reduces biodiversity. [2 marks]
- Cue. Growing a single crop removes varied habitats and food sources, so fewer species can live there.
Q3. Explain why it is the decomposing bacteria, not the algae, that cause the oxygen to fall during eutrophication. [2 marks]
- Cue. The bacteria multiply on the dead algae and plants and respire aerobically, using up dissolved oxygen as they decompose the organic matter.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20185 marksExplain how the leaching of fertiliser into a river can lead to the death of fish through eutrophication.Show worked answer →
Excess nitrate (and phosphate) fertiliser is leached into the river, enriching the water with nutrients.
This causes a rapid growth of algae (an algal bloom) at the surface that blocks light to plants below, which then die.
Decomposing bacteria feed on the dead plants and algae, multiply, and use up dissolved oxygen in aerobic respiration.
The fall in dissolved oxygen means fish and other aerobic organisms cannot respire and die; this is why a polluted river has a low oxygen content and low diversity.
Markers reward leaching of nutrients, algal bloom blocking light, decomposers using oxygen, and the resulting oxygen shortage killing fish.
WJEC 20214 marksDiscuss two reasons why conserving biodiversity is important, and outline one method used to conserve a threatened species.Show worked answer →
Biodiversity is important economically and ecologically: many medicines and crops come from wild species, and a diverse ecosystem is more stable and resilient because food webs have more alternative pathways, so the loss of one species is less likely to cause collapse.
A second reason is genetic: a wide gene pool gives species the variation needed to adapt to change such as new diseases or climate shifts.
One conservation method is captive breeding and reintroduction, where a threatened species is bred in zoos or reserves to increase numbers and genetic diversity before being released back into protected habitat; seed banks and protected areas are also acceptable.
Markers reward two valid reasons (economic, ecological stability or genetic) and one correctly described conservation method.
Related dot points
- Ecosystems, energy flow and nutrient cycles, population growth and the factors that limit it, and succession.
A focused answer to WJEC A-Level Biology Unit 3, covering ecosystems and trophic levels, energy flow and the carbon and nitrogen cycles, population growth and limiting factors, and succession.
- The role of ATP, the light-dependent and light-independent reactions of photosynthesis, and the factors that limit the rate.
A focused answer to WJEC A-Level Biology Unit 3, covering the role of ATP, the light-dependent reactions and photophosphorylation, the light-independent Calvin cycle, and the factors limiting the rate of photosynthesis.
- The principles of classification and phylogeny, the three domains and five kingdoms, biodiversity, and how to measure species diversity.
A focused answer to WJEC A-Level Biology Unit 2, covering the hierarchy of classification, the binomial system, the three domains and five kingdoms, phylogeny, biodiversity and the index of diversity.
- The structure of bacteria, aseptic technique, culturing microorganisms, the growth curve, and methods of measuring growth.
A focused answer to WJEC A-Level Biology Unit 3, covering bacterial structure, aseptic technique, culturing microorganisms in batch and continuous culture, the bacterial growth curve, and methods of measuring microbial growth.
- Glycolysis, the link reaction, the Krebs cycle, oxidative phosphorylation, and anaerobic respiration.
A focused answer to WJEC A-Level Biology Unit 3, covering glycolysis, the link reaction, the Krebs cycle, oxidative phosphorylation and the electron transport chain, and anaerobic respiration in animals and yeast.
Sources & how we know this
- WJEC A-level Biology specification — WJEC (2015)