Global protected areas and IUCN designations: Do the categories match the conditions?

Protected areas are considered fundamental to the preservation of nature. The International Union for Conservation of Nature (IUCN) has standardized categories for protected areas designation, which are intended to represent varying levels of regulatory protection. We evaluate whether the present assignment of protected areas to IUCN categories corresponds to the expected gradient of naturalness in a globally consistent manner. Our proxy of naturalness was a global map of human influence known as Human Footprint (HF). Higher HF values represent less intact natural areas. Our final sample of protected areas included 21,186 IUCN-designated sites that were >= 1 km(2). We used multiple linear regression to test for the effect of IUCN categories on mean HF while accounting for biome and protected area size. The present assignment of protected areas to IUCN categories does not correspond to the expected gradient of naturalness. We observed that IUCN Category la areas have higher HF than expected and Category VI protected areas have unexpectedly low HF; Category VI protected areas also are generally larger than protected areas of other categories. Reporting of area protected in different IUCN categories is one measure of progress towards meeting commitments under the Convention on Biological Diversity, yet because IUCN categories are not interpreted consistently across the globe, this is not a reliable metric. Further, despite the social, economic and ecological importance of protected areas with a very low HF, our results suggest that the availability of such areas within the global protected areas network is very limited. (C) 2009 Elsevier Ltd. All rights reserved.