Students should be able to describe both positive and negative human…

The idea

Human interactions with an ecosystem can raise or lower biodiversity. Negative interactions include deforestation, draining peat bogs, overfishing, pollution and building on greenfield land; each removes habitats, food or breeding sites, so species numbers and variety fall. Positive interactions include replanting woodland, restoring wetlands, creating hedgerows and wildlife corridors, reducing pollution and setting aside nature reserves. To describe, name the interaction and say what changes in the ecosystem. To explain, link that change to species survival: fewer habitats means fewer niches, so populations shrink and some species disappear locally.

For example: Clearing hedgerows removes nesting sites and insect food, lowering bird diversity.

What earns the marks

• Names a negative interaction such as deforestation, peat extraction, overfishing, pollution or urban expansion and states the habitat or resource lost.
• Names a positive interaction such as reforestation, wetland restoration, hedgerow planting, wildlife corridors or pollution reduction and states the habitat or resource gained.
• Explains the impact on biodiversity by linking habitat change to the number of available niches, so species variety and population sizes rise or fall.
• Uses a specific example, such as hedgerow removal reducing nesting sites and insect food so bird diversity falls.
• Distinguishes local effects, such as one pond being polluted, from wider effects, such as a river catchment losing several species.
• Applies the terms biodiversity, ecosystem, habitat, species and population correctly when describing the interaction.

Common mistakes and how to put them right

• Treating any planting as automatically positive.

  Put it right: State which species benefit and why, because planting a single non-native species can reduce variety.

• Confusing habitat loss with extinction.

  Put it right: Habitat loss lowers biodiversity and may cause local extinction, but global extinction needs wider evidence.

• Describing an interaction without its impact.

  Put it right: Add the consequence for species number or population size, not just the activity.

Exam tips

• Use a two-part answer: first describe the interaction, then explain the biodiversity impact using because or so.
• Choose one negative and one positive interaction and develop each with a named organism or habitat.
• Link answers to niches and habitats; these ideas carry the explanation beyond simple description.