# The Theory of Island Biogeography

*MacArthur · Ecological, Complexity & Systems · Princeton University Press · 1967 · Paywalled*

An equilibrium theory of how many species an island holds, and one of the more transferable pieces of ecology on this map. MacArthur and Wilson argue that species richness settles where the immigration rate of new species balances the extinction rate of resident ones, and that both are governed by geometry rather than by which species happen to be involved. Immigration falls with distance from the mainland, because fewer colonists make the crossing. Extinction rises as area shrinks, because small populations are more easily lost. Near and large islands therefore carry more species than far and small ones, and the number holds roughly steady while the composition keeps turning over, which is the counter-intuitive part: a stable count concealing constant replacement. The organisational reading is direct and unflattering. A team isolated from the rest of an organisation receives fewer new practices and loses the ones it has faster, so its repertoire thins regardless of the quality of the people in it, and the thinning is a property of position rather than of merit. Siloing an organisation is fragmentation, and fragmentation reduces variety on both sides of the equation at once. The corpus's arguments about ecotones, edge effects and the value of contact between differing groups are the same claim from the other direction, and Ashby's law says why variety loss is not merely a shame. Limits are real: the theory predicts numbers rather than which species, its equilibrium assumption has been heavily revised, and the reserve design debate it launched was never cleanly settled. Read it for the mechanism, which is robust, rather than for the equilibrium, which is not.

- **This page:** https://explore.psychsafety.com/n/macarthur-wilson-1967/
- **View the source paper:** https://press.princeton.edu/books/paperback/9780691088365/the-theory-of-island-biogeography
- **Interactive map:** https://explore.psychsafety.com/?mode=papers&node=macarthur-wilson-1967

## Neighbours (8)

- [An Introduction to Cybernetics](https://explore.psychsafety.com/n/ashby-1956.md) (paper)
- [Resilience and Stability of Ecological Systems](https://explore.psychsafety.com/n/holling-1973.md) (paper)
- [Ecosystems and the Biosphere as Complex Adaptive Systems](https://explore.psychsafety.com/n/levin-1998.md) (paper)
- [The Use and Abuse of Vegetational Concepts and Terms](https://explore.psychsafety.com/n/tansley-1935.md) (paper)
- [Organisational Fabric](https://explore.psychsafety.com/n/the-organisational-fabric-of-psychological-safety.md)
- [Ecotones & Edge Effect](https://explore.psychsafety.com/n/psychological-safety-59-ecotones-the-edge-effect.md)
- [Five Ecological Concepts](https://explore.psychsafety.com/n/five-ecological-concepts-for-working-in-organisational-change.md)
- [Safety Organised Criticality](https://explore.psychsafety.com/n/safety-organised-criticality-socy.md)