# Food Web Complexity and Species Diversity

*Paine · Ecological, Complexity & Systems · The American Naturalist · 1966 · Paywalled*

The experiment behind the keystone species concept, and the demonstration that importance can be disproportionate to abundance and invisible until removal. Paine spent years prising the predatory starfish Pisaster ochraceus off a stretch of rocky shore at Mukkaw Bay, Washington, and throwing it into the sea, while leaving an adjacent stretch alone. On the untouched shore, a diverse community persisted; on the cleared shore, the mussels the starfish had been eating spread unchecked, crowded out the other species, and the community collapsed from fifteen species toward a mussel monoculture. The predator had not been dominant by numbers or biomass, but its selective consumption of the competitively superior species was the thing holding the space open for everything else, and nothing about its everyday presence announced that role. The term keystone species itself arrives in Paine's short 1969 follow-up note, but this is the experiment the term names. Three transferable claims follow. Structural importance cannot be read from prominence: the member whose ordinary activity holds space open for others may look unremarkable until they are gone, and by then the reorganisation is under way. Removal is a regime shift, not a subtraction: the cleared shore did not become the same community minus one species, it became a different community, which is the alternative-stable-states argument Scheffer later generalised. And you learn structure by perturbation, which is methodologically clean on a shoreline and ethically loaded in an organisation, where the equivalent experiment is run constantly, unintentionally, by restructures. The critical read the field supplied is worth keeping: keystone became a conservation buzzword applied so loosely that Mills, Soule and Doak argued in 1993 for retiring it, and later work showed Pisaster's effect is context-dependent, strong on wave-exposed shores and weak in sheltered ones, so even the canonical keystone is keystone only somewhere. The concept survives as a question to ask, not a label to award.

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## Neighbours (4)

- [Early-warning signals for critical transitions](https://explore.psychsafety.com/n/scheffer-et-al-2009.md) (paper)
- [Looking At Things Properly](https://explore.psychsafety.com/n/a-practical-guide-to-looking-at-things-properly.md)
- [Organisational Fabric](https://explore.psychsafety.com/n/the-organisational-fabric-of-psychological-safety.md)
- [Five Ecological Concepts](https://explore.psychsafety.com/n/five-ecological-concepts-for-working-in-organisational-change.md)