Prioritizing rare climate space enhances plant biodiversity in national conservation area networks

Protected areas (PAs) planning often encounters obstacles globally due to the scarcity of reliable and systematic biodiversity data covering wide areas. Understanding the interaction between climate and biodiversity patterns can offer a novel approach to spatial conservation prioritization, considering the impact of climate on species distributions and the global availability of climate data. Here we used climate-based planning to develop national networks of PAs by prioritizing "climate space", which represents the multidimensional climatic conditions in a specific area. We assessed four climate-selecting strategies using Marxan to enhance average plant species richness and species composition' s complementarity in candidate PAs: (1) random selection; (2) prioritizing rare climates; (3) prioritizing common climates; and (4) equal representation for each climate condition. We identified the spatial heterogeneity of national climate conditions in South Korea, with unique climates shaped by geographic and topographic diversity. Notably, prioritizing rare climates consistently resulted in higher average plant species richness and complementarity within candidate PAs. Rare climates exhibited high spatial similarity with high plant species richness and showed significant overlaps and strong connectivity to existing PAs. Rare climatic zones in South Korea have greater geodiversity and lower human population density, providing opportunities for distinct ecosystems and habitats for rare species. Our methodology, which can be easily replicated, offers spatial-explicit and quantitative prioritization of resource allocation in a nation or region with limited biological data.