How do human activities reduce biodiversity, and how can it be protected?
Human influences on biodiversity: habitat loss and fragmentation, overexploitation, the impact of invasive non-native species, pollution, and the methods used to conserve and protect biodiversity.
An SQA Higher Environmental Science answer on human influences on biodiversity, covering habitat loss and fragmentation, overexploitation, invasive non-native species, pollution, and conservation methods such as protected areas, captive breeding and legislation.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
The SQA wants you to explain the main ways human activity reduces biodiversity - habitat loss and fragmentation, overexploitation, invasive non-native species and pollution - and to describe the methods used to conserve and protect biodiversity. This applies the ideas of the Living Environment to the real pressures driving species loss.
Habitat loss and fragmentation
The single largest cause of biodiversity loss is the destruction of habitat for agriculture, building, forestry and mining.
Fragmentation harms biodiversity in several ways: small patches support small populations with low genetic diversity and a high chance of local extinction; isolation prevents movement between patches so populations cannot interbreed or be re-colonised; and small patches have more edge, where conditions differ from the interior, shrinking the usable core habitat.
Overexploitation
Overexploitation is harvesting a species faster than it can reproduce, so its population falls. Examples include overfishing (taking fish faster than the stock can replace itself), hunting for trophies, meat or the wildlife trade, and unsustainable logging. Without limits, overexploitation can drive a species to commercial or complete extinction.
Invasive non-native species
Invasive species are damaging because they typically arrive without their natural predators, parasites or diseases, so their numbers grow unchecked. They then outcompete native species for resources, prey on natives that have no defences, or spread disease. As native populations collapse, biodiversity falls. Familiar UK examples include the grey squirrel, which outcompetes the native red squirrel and carries a virus lethal to it, and Japanese knotweed, which crowds out native plants.
Pollution
Pollution degrades habitats and disrupts food webs. Key forms include eutrophication (nutrient enrichment of water from fertiliser run-off, which causes algal blooms that strip oxygen and kill aquatic life), toxic chemicals and pesticides that can bioaccumulate up food chains to harm top predators, plastic waste, and acidification of soils and water. Pollution can lower biodiversity even where the habitat itself is left intact.
Conserving and protecting biodiversity
Conservation uses several complementary methods:
- Protected areas (national parks, nature reserves, marine protected areas) safeguard habitats, and wildlife corridors reconnect fragmented patches so populations can mix.
- Captive breeding and reintroduction boost numbers of endangered species (often supported by seed banks and gene banks to preserve genetic diversity), then return them to the wild.
- Control or eradication of invasive species protects natives.
- Sustainable harvesting (fishing quotas, mesh-size and closed-season rules, selective logging) keeps exploitation within the rate of replacement.
- Habitat restoration rebuilds degraded ecosystems.
- Legislation and international agreements (for example CITES, which regulates trade in endangered species, and national protection laws) give species and habitats legal protection.
Examples in context
Example 1. The Atlantic cod collapse. Off Newfoundland, decades of catches above the replacement rate collapsed the cod stock in the early 1990s despite warnings, forcing a fishing moratorium and the loss of tens of thousands of jobs. The stock has been slow to recover, a stark illustration of overexploitation and why catch quotas matter.
Example 2. Red squirrel conservation in Scotland. Programmes such as Saving Scotland's Red Squirrels combine controlling the invasive grey squirrel, protecting core woodland habitat and monitoring squirrelpox. The mix of invasive-species control, habitat protection and disease surveillance shows conservation matching several methods to the specific threats facing a native species.
Try this
Q1. Name three human activities that reduce biodiversity. [3 marks]
- Cue. Any three of: habitat loss or fragmentation, overexploitation, introducing invasive species, pollution.
Q2. Explain how a wildlife corridor helps a fragmented population. [2 marks]
- Cue. It reconnects isolated patches so individuals can move, interbreed and recolonise, maintaining gene flow.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher specimen4 marksExplain how habitat fragmentation, as opposed to simple habitat loss, threatens biodiversity.Show worked answer →
A 4-mark explain answer needs the specific effects of breaking a habitat into pieces.
Fragmentation divides a large continuous habitat into small, isolated patches. Each patch supports a smaller population, which has lower genetic diversity and a higher risk of local extinction by chance.
Isolation prevents movement between patches, so populations cannot interbreed and lost individuals cannot be replaced by migration from elsewhere, reducing gene flow and increasing inbreeding.
Small patches also have proportionally more edge, where conditions (light, wind, temperature, invasive species and predators) differ from the interior, so the usable core habitat shrinks further.
Markers reward smaller isolated populations, reduced gene flow or movement, the higher extinction risk, and the edge effect.
SQA Higher specimen3 marksExplain why an invasive non-native species can reduce the biodiversity of an ecosystem it is introduced into.Show worked answer →
This is a 3-mark explain answer about invasive species.
An invasive non-native species often has no natural predators, parasites or diseases in the new ecosystem, so its population can grow rapidly and unchecked.
It then outcompetes native species for resources such as food, light or space, or it may prey on or spread disease to native species that have no defences against it.
As native populations fall or are lost, the diversity of the ecosystem decreases.
Markers reward the lack of natural controls, the mechanism of harm (competition, predation or disease), and the resulting fall in native biodiversity.
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Sources & how we know this
- Higher Environmental Science Course Specification (C826 76) — SQA (2021)
- Higher Environmental Science course overview and resources — Qualifications Scotland (2026)