Protected area downgrading, downsizing, and degazettement (PADDD) in Africa, Asia, and Latin America and the Caribbean, 1900–2010

National parks, nature reserves, and other protected areas (PAs) are the centerpiece of efforts to conserve biodiversity. Conservation policy and practice assume that PAs are permanent institutions, but scattered evidence suggests widespread PA downgrading, downsizing, and degazettement (PADDD). To assess the extent, patterns, trends, causes, and consequences of PADDD, we reviewed authoritative United Nations lists of PAs (1962–2009), examined published documents, and consulted 128 conservation experts. We focused on Africa, Asia, Latin America, and the Caribbean, which collectively contain most global priorities for conservation and more than 70% of the global PA estate. We identified 543 instances of PADDD in 57 countries, affecting more than 503 591 km2 of protected lands and waters. The occurrence, spatial extent, timing, proximate causes, and consequences of PADDD varied widely among countries. Of the 375 PAs affected by PADDD, 76 PAs (20.3%) were affected more than once. Thirty (5.5%) of the 543 PADDD events were eventually partially or wholly reversed. In the absence of PA downsizing and degazettement, at least four additional countries would have already met 2020 targets for PA coverage established under the Convention on Biological Diversity. Our findings suggest that PADDD is a patchy, episodic phenomenon associated with industrial-scale natural resource extraction and development; local land pressures and land claims; and conservation planning. Though some PADDD events may foster biodiversity conservation, most PADDD suggests tradeoffs between conservation goals and other policy objectives. PADDD thus represents both a largely unrecognized threat to biodiversity and a rarely employed mechanism to strengthen conservation policy.