Increasingly severe storms and weaker carbonate materials associated with more acidic oceans will increase the vulnerability of reef corals to mechanical damage. Mechanistic predictions based on measurements of colony mechanical vulnerability and future climate scenarios demonstrate dramatic shifts in assemblage structure following hydrodynamic disturbances, including switches in species' dominance on the reef and thus potential for post-disturbance recovery. Larger colonies are more resistant to factors such as disease and competition for space, and complex morphologies support more associated reef species. Future reefs are thus expected to have lower colony abundances and be dominated by small and morphologically simple, yet mechanically robust species, which will in turn support lower levels of whole-reef biodiversity than do present-day reefs.