Global gap analysis of cactus species and priority sites for their conservation

Knowing how much biodiversity is captured by protected areas (PAs) is important to meeting country commitments to international conservation agreements, such as the Convention on Biological Diversity, and analyzing gaps in species coverage by PAs contributes greatly to improved locating of new PAs and conservation of species. Regardless of their importance, global gap analyses have been conducted only for a few taxonomic groups (e.g., mangroves, corals, amphibians, birds, mammals). We conducted the first global gap analysis for a complete specious plant group, the highly threatened Cactaceae. Using geographic distribution data of 1438 cactus species, we assessed how well the current PA network represents them. We also systematically identified priority areas for conservation of cactus species that met and failed to meet conservation targets accounting for their conservation status. There were 261 species with no coverage by PAs (gap species). A greater percentage of cacti species (18%) lacked protection than mammals (9.7%) and birds (5.6%), and also a greater percentage of threatened cacti species (32%) were outside protected areas than amphibians (26.5%), birds (19.9%), or mammals (16%). The top 17% of the landscape that best captured covered species represented on average 52.9% of species ranges. The priority areas for gap species and the unprotected portion of the ranges of species that only partially met their conservation target (i.e., partial gap) captured on average 75.2% of their ranges, of which 100 were threatened gap species. These findings and knowledge of the threats affecting species provide information that can be used to improve planning for cacti conservation and highlight the importance of assessing the representation of major groups, such as plants, in PAs to determining the performance of the current PA network.