Optimal species preservation policy in a symbiotic relationship between species

Biodiversity is defined as the variety within the living world, and describes the relationships between the species, within ecosystems and beyond. The relationships between the species are often very important to the construction of the habitat’s biodiversity. According to the predominant opinion in both economics and ecology, damage to a certain species in the habitat could negatively affect the harmony of the habitat and of the species that depend on it. As Berlow et al. (1999) state, ‘understanding how the strengths of species interactions are distributed among species is critical for developing predictive models of natural food webs as well as for developing management and conservation strategies’ (p. 2206). Financial resources for biodiversity conservation programs are not sufficient to protect all habitats and species. This situation requires choosing conservation priorities in order to support the most species at the least cost. Moran et al. (1996, 1997) note that no single correct method exists for establishing biodiversity conservation priorities at any level of organization. Nevertheless, the question of how to determine priorities for maintaining or increasing biodiversity under a limited budget constraint has concerned environmental economists since the seminal work by Weitzman (1998). He developed ‘a more-or-less consistent conceptual framework and a more-or-less usable measure on the value of diversity that can tell us how to trade off one form of diversity against the other’ (Weitzman, 1995, p. 21).