9.5 Measuring and Managing Biodiversity

2026 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Describe and evaluate methods for estimating biodiversity
  2. Apply sampling techniques to unfamiliar situations
  3. Evaluate national and international strategies for conserving the biodiversity and genetic resources of natural ecosystems
  4. Understand key tools and examples including: pitfall traps, pooters, quadrats, transects, random and systematic sampling, sustainable harvesting, sustainable forestry/agroforestry, national parks, wildlife/ecological reserves and corridors, extractive reserves, world biosphere reserves, seed banks, zoos and captive breeding, sustainable tourism and ecotourism

Part 1: What Is Biodiversity?

https://cambridgeassistant.com

Biodiversity means the variety of living things in an area. It includes:

  • Species diversity — how many different species live in an area, and how many individuals of each species there are
  • Genetic diversity — the range of different genes within a species (so not all individuals are exactly the same)
  • Ecosystem diversity — the variety of different habitats and ecosystems in a region (e.g. forests, wetlands, grasslands)

A healthy ecosystem usually has high biodiversity — many different species living together. When biodiversity falls, ecosystems become fragile and less able to cope with change.

Part 2: Methods for Estimating Biodiversity

https://cambridgeassistant.com

Because it is impossible to count every single living thing in an area, scientists use sampling — studying a small part of the area and using the results to estimate what is happening in the whole area.

2.1 Sampling Techniques for Animals

Pitfall Traps

  • A pitfall trap is a container (like a jar or cup) buried in the ground with its opening level with the soil surface.
  • Small animals such as beetles, ants, spiders, and other invertebrates (animals without backbones) fall in and cannot climb out.
  • Scientists check the trap regularly, record what they find, and then release the animals.
  • Advantage: Simple and cheap to set up; works continuously without a person watching.
  • Limitation: Only catches small ground-dwelling animals; animals may be harmed if not checked often.

Pooters

  • A pooter (also called an aspirator) is a small jar with two tubes. The scientist sucks on one tube, which draws small insects from the ground or leaf litter into the jar through the other tube.
  • A piece of gauze (fine mesh) inside the jar stops insects from being sucked into the scientist's mouth.
  • Advantage: Useful for collecting tiny, delicate insects without damaging them.
  • Limitation: Only collects very small animals; time-consuming for large areas.

Quadrats

  • A quadrat is a square frame (often 0.5 m × 0.5 m or 1 m × 1 m) placed on the ground.
  • Scientists count every species inside the frame — usually used for plants, slow-moving animals, or animals attached to surfaces (like limpets on a rock).
  • Results from many quadrats are averaged to estimate the species variety across the whole area.
  • Advantage: Quick and easy to use; gives clear data on plant communities.
  • Limitation: Not suitable for fast-moving animals; small quadrats may miss rare species.

Transects

  • A transect is a straight line drawn across a habitat (using a tape measure or rope).
  • Scientists record every species they find along that line or within a set distance on either side.
  • Belt transect: A strip of measured width along the line — everything inside the strip is recorded.
  • Line transect: Only organisms touching the line are recorded.
  • Transects are especially useful for studying how species change across an environmental gradient (e.g. from the sea shore to inland, or from a sunny clearing into a shaded forest).
  • Advantage: Excellent for showing how species change from one place to another.
  • Limitation: Only covers a narrow strip — may miss what is happening away from the line.

Sign in to view full notes