Comparing Methods for Prioritising Protected Areas

There are insufficient resources available to manage the world’s existing protected area portfolio effectively, so the most important sites should be prioritised in investment decision-making. Sophisticated conservation planning and assessment tools developed to identify locations for new protected areas can provide an evidence base for such prioritisations, yet decision-makers in many countries lack the institutional support and necessary capacity to use the associated software. As such, simple heuristic approaches such as species richness or number of threatened species are generally adopted to inform prioritisation decisions. However, their performance has never been tested. 

A group of colleagues from Madagascar and the UK now evaluated the performance of some site prioritisation protocols that used to rank the conservation value of 22 established and candidate protected areas of dry forest in Madagascar. The organisms of choice were reptiles for which there is comprehensive inventory data available from a range of sites in the contiguous dry regions of Madagascar. The country’s reptile fauna is very diverse, comprising almost 400 species, most of which are endemic (92%) and forest-dependent. Given the dramatic deforestation in Madagascar, such species may depend on the effective maintenance of protected areas for their long-term survival.

The authors tested if their rankings produced by four different protocols correlated with the results of a widely-used systematic conservation planning software called Zonation. The four indices scored sites on the basis of: 

• species richness 
• an index based on the species’ Red List status;
• irreplaceability (a key metric in systematic conservation planning, where each species is weighted by the inverse of the number of protected areas in which it was recorded); 
• a novel Conservation Value Index (CVI), which incorporates species-level information on endemism, representation in the protected area system, tolerance of habitat degradation and hunting/collection pressure.

All of the rankings correlated with the software results, but the CVI and Irreplaceability performed better than Species Richness and the Red List Index which lets the authors conclude:

Given that management is limited by insufficient financial resources, it is all the more critical that available funds are targeted towards the most important sites. While sophisticated analytical tools can and should be used to inform such investment decisions, decision-makers often lack the capacity to use them, or choose not to for other reasons. Instead, they frequently rely on non-transparent, subjective processes or simple measures such as species richness or the number of threatened species. It is therefore important to understand how such metrics can perform and in what circumstances they should be used. Our analysis suggests that some heuristic indices can provide a transparent framework to support evidence-based decision-making by practitioners, although their performance is variable and partially dependent on the amount of information required to use them. Our CVI, which incorporates measures of rarity and threat for individual species, appears to provide a useful alternative to more sophisticated systematic conservation planning tools, and emphasises the benefits of integrating species-specific data into conservation assessments.