Edge artefacts and lost performance in national versus continental conservation priority areas.

Aim Global conservation policies, such as the Convention on Biological Diversity ( CBD) decision to aim for the protection of 17% of the area of terrestrial ecosystems by 2020, are typically realized at national levels. We investigate the difference between continentally coordinated conservation versus nationally devolved conservation, in a manner relevant for the Nagoya resolution. Location The terrestrial areas of the Western Hemisphere. Methods We used IUCN distribution data for 8463 species of mammals, birds and amphibians in the Western Hemisphere. We investigated the consequences of prioritizing land at a continental scale, versus analysing priorities within each country separately. Spatial prioritization was performed using the Zonation software, which produces a complementarity-based hierarchical priority ranking across the area of interest. Results We found that coordinated continent-wide priorities achieved > 50% higher mean protection levels than national analyses for the top 17% of land. National prioritizations also result in spatial priority patterns that can be considered as artefacts at the continental scale: in bands of high-priority land concentrated at terrestrial political boundaries, such as at low-latitude edges of temperate zone countries. We find that this edge artefact also correlates with the present distribution of conservation areas, with the density of conservation areas within 50 km of a national border being > 50% higher than the density of conservation areas away from national borders. Main conclusions The means by which national priorities are integrated with continental or global conservation prioritization will have considerable influence on how much is achieved by the CBD resolution. Focus on national species distributions and priorities will result in lost performance because of emphasis on nationally rare species that are comparatively common elsewhere. National borders intersect species distributions (and possibly diversity gradients), leading to clustering of nationally rare species and priority areas close to the border. [ABSTRACT FROM AUTHOR]