The usefulness of surrogates in biodiversity conservation: A synthesis

Abstract

Preserving biodiversity requires extensive information on species distributions and effectiveness of conservation actions. A surrogate approach, where a small number of species act as surrogates for broader groups of species, can simplify this task. Types of surrogates include indicator, umbrella, keystone and flagship species, and using diversity of higher taxonomic levels to represent species diversity. An overview of the empirical evidence of the usefulness of surrogates as a conservation tool is missing. We synthesised knowledge on if and when surrogate species are useful by systematically searching for meta-analyses and literature reviews assessing this. Results from 34 reviews revealed weak correlations between diversity of indicator species and other species and that umbrella species were not consistently useful for prioritising conservation actions. However, diversity of higher taxonomic levels can be representative of species diversity. No reviews have assessed the usefulness of keystone or flagship species. Thus, surrogate taxa often do not represent biodiversity or threatened species, and conservation actions aimed at surrogates might not necessarily benefit other species. However, surrogates are more likely to be useful when using a higher-taxon approach, when strong ecological similarities exists between a surrogate and other species, when surrogates are used at regional or landscape rather than local scales, and when using sets of multiple species as surrogates. As some use of surrogate species will always be necessary, surrogates should be carefully selected and their usefulness and cost-effectiveness should be assessed, including the risk that conservation actions aimed at that surrogate have unintended effects on other species.