Assessing the performance of surrogate species in spatial conservation planning

Selecting effective surrogate species is essential for improving conservation planning efficiency under limited resources. However, the selection process is often hindered by conceptual ambiguities and inconsistent methodologies. Moreover, most existing studies focus on assessing surrogate species but fail to integrate them into practical spatial conservation planning. We developed a multidimensional effectiveness index (EI) that integrates umbrella, keystone, flagship, and protection dimensions to quantitatively evaluate the conservation potential of mammal species. Applying this framework to 346 mammal species in China, we ranked species by EI and incorporated top-performing subsets into systematic spatial prioritization with Zonation, with condition and cost layers representing climate vulnerability and human pressure, respectively. We assessed surrogate performance across 4 planning scenarios and 10 selection thresholds. Species with high EI scores achieved up to 80% or greater spatial representation based only on the 20-30% of species with the highest EI scores, substantially improving planning efficiency. The resulting priority conservation areas (PCAs) covered approximately 2.69 million km², accounting for ∼28% of China's land area. The PCAs were concentrated in biodiversity hotspots such as the Hengduan Mountains, southeastern Xizang, Yunnan, northeastern China, and Taiwan. Most of China's pilot national parks overlapped with the identified PCAs, underscoring the ecological validity of the framework. This study bridges the gap between species-level assessments and spatial conservation planning. The proposed framework is flexible and broadly applicable, offering a practical tool to optimize surrogate selection and support national and global biodiversity targets.