3.4 Island Biogeography - Data Analysis

This is a good exercise to have students engage with a simple concept that has a tricky graph behind it. It's a seminal graph produced by the scientists who proposed this theory but helps explore ideas of protected area design.

Island Biogeography

Ecologists have established clear links between habitat fragmentation and species extinction.

Therefore larger reserves are usually much more valuable for conserving species than smaller ones.

Important decisions have to be made about the optimum size, shape, pattern and geographical coverage of reserves often based on principles of island biogeography.

The image shows the number of species found on an island based on the rate of immigration (to the island), the rate of extinction (on the island), the distance from the mainland and the size of the island.

Here's a great video from HHMI Biointeractive about Island Biogeography and Conservation. It's about 18m long.

Student Questions:

  1. How does the rate of immigration differ between islands close to the mainland and those far from the mainland?
  2. How does the rate of extinction differ between small islands and large islands?
  3. Suggest some reasons why this might be the case.
  4. What is the combination for high biodiversity and how can this idea be applied in general to protected areas?

Click on the hidden box for answers.

  1. The rate of immigration is higher closer to the mainland. The further from the mainland, the lower the rate if immigration.
  2. The rate of extinction is higher on smaller islands than larger islands.
  3. This might be due to a lack of food / insufficient breeding opportunities / inbreeding depression / random (stochastic) events / lack of suitable habitat / increased competition.
  4. Big islands nearer the mainland have the best chances of maintaining high diversity. Thus, for protected area, you want the largest area possible with the best connections to other areas of high biodiversity such as habitat corridors and buffer zones.
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