Empirical evidence for reduced protection levels across biodiversity features from target-based conservation planning

Target-based planning is an integral component of systematic conservation planning. Using empirical data, we investigate a prior conceptual proposition that target-based planning may lead to lower average protection levels across biodiversity features due to its prescriptive nature where conservation outcome is measured in terms of achievement of many independently developed targets. We used spatial distribution models and externally provided targets set for 253 biodiversity features from the Maputaland–Pondoland–Albany hotspot and compared target-based planning to alternative approaches, such as maximum-utility planning, which can operate without the specification of strict targets. We found that target-based planning retained on average a significantly lower fraction of the distributions of all biodiversity features than did alternative methods. This sub-optimality fundamentally follows from the nestedness of species distributions being ignored in target setting, leading to investment in features that occur in relatively species-poor and expensive areas. Consequently, benefit-based alternatives to target-based planning will achieve higher overall conservation performance.