global protected area expansion is compromised by projected landuse and parochialism protected areas are one of the main tools for halting the continuing global biodiversity crisis caused by habitat loss fragmentation and other anthropogenic pressures according to the aichi biodiversity target 11 adopted by the convention on biological diversity the protected area network should be expanded to at least 17 of the terrestrial world by 2020 to maximize conservation outcomes it is crucial to identify the best expansion areas here we show that there is a very high potential to increase protection of ecoregions and vertebrate species by expanding the protected area network but also identify considerable risk of ineffective outcomes due to landuse change and uncoordinated actions between countries we use distribution data for 24757 terrestrial vertebrates assessed under the international union for the conservation of nature iucn red list of threatened species and terrestrial ecoregions 827 modified by landuse models for the present and 2040 and introduce techniques for global and balanced spatial conservation prioritization first we show that with a coordinated global protected area network expansion to 17 of terrestrial land average protection of species ranges and ecoregions could triple second if projected landuse change by 2040 ref 11 takes place it becomes infeasible to reach the currently possible protection levels and over 1000 threatened species would lose more than 50 of their present effective ranges worldwide third we demonstrate a major efficiency gap between national and global conservation priorities strong evidence is shown that further biodiversity loss is unavoidable unless international action is quickly taken to balance landuse and biodiversity conservation the approach used here can serve as a framework for repeatable and quantitative assessment of efficiency gaps and expansion of the global protected area network globally regionally and nationally considering current and projected landuse pressures