 Callum has served on a US National Research Council Committee on Marine Protected Areas and has also been a member of the Marine Reserves Working Group, headed up by Jane Lubchenco, Steve Gaines and Steve Palumbi at the National Center for Ecological Analysis and Synthesis in Santa Barbara.With this group he sought to develop a more robust theoretical underpinning for the design and implementation of marine reserves.In parallel with work on reserves, Callum has also been active with the Coral Reef Fish Specialist Group of the World Conservation Union (IUCN).