Using habitat suitability models to scale up population persistence targets

Setting operational targets for the protection of species is crucial for identifying conservation priorities and for monitoring conservation actions’ effectiveness. The use of quantitative targets for global species conservation has grown in the past ten years as a response to the commitment of reducing extinction rates established by the Convention on Biological Diversity. We reviewed the use of conservation targets in global scale conservation analyses, and found that most of the publications adopted species representation targets, corresponding to an amount of area to be protected. We found no work adequately targeting species’ persistence, i.e. the complement to species extinction risk. Despite the adoption of pragmatic population targets, consisting in a number of individuals to be protected, has been recently proposed for global species conservation, the use of these targets at the species level is not always warranted. Pros and cons of using population persistence targets for species conservation have been discussed, yet the fundamental issue of how to scale these targets from populations to species is still unresolved. We discuss the process of “scaling up” population persistence targets to the species level using habitat distribution models, and test our approach in a case study on the European ground squirrel (Spermophilus citellus). We identified three main steps to be followed: (i) definition of a population target, (ii) characterisation of the species’ populations by means of a habitat suitability model, and (iii) definition of a scaled species target. An up-scaled species target should include multiple conditions reflecting species persistence (number, size, location of the populations to be protected), uniqueness (e.g. evolutionary potential) and representativeness (e.g. presence in different ecosystems). Adopting scaled up species persistence targets within conservation planning approaches can allow protected area plans to give the highest contribution to reducing global species extinction risk.