Exercises: Simpson's Diversity Index

Define biodiversity and state what is meant by species richness and species evenness. Explain why a high value of Simpson's Diversity Index indicates a more diverse habitat when the index is calculated as $D = 1-\sum\left(\frac{n}{N}\right)^2$.

Farm A is an intensive ryegrass monoculture with $D = 0.12$. Farm B is a mixed organic farm with hedgerows and wildflower margins, with $D = 0.78$.

1. a) Explain why a monoculture has a low index.

1. b) Discuss two ecological consequences of the difference for pollinators and soil health.

1. c) A researcher claims that Farm B is always better for conservation. Evaluate this claim, considering that $D$ ignores which species are present.