A complicated debate among conservation biologists (also known as the SLOSS debate) focused on whether it is better to create one large or several small reserves. The species area relationship formula_1 states that the number of species in a habitat is directly proportional to its size. So theoretically if several small reserves have a greater total area than a single large reserve, the small reserves will contain a greater total number of species. This, combined with assumptions of island biogeography theory, lead Jared Diamond to state that a single large reserve is the best method of conservation, and it is still commonly recommended. For example, a review by Ovaskainen determined that a single large reserve site is best at maximising long-term survival of the species and deferring extinction in a closed population.