LETTER Examining protected area effectiveness in Sumatra: importance of regulations governing unprotected lands D. L. A. Gaveau 1,2 , L. M. Curran 1,3 , G. D. Paoli 4 , K. M. Carlson 1,3,5 , P. Wells 4 , A. Besse-Rimba 6 , D. Ratnasari 2 , & N. Leader-Williams 7 1 Woods Institute for the Environment, Stanford University, 473 Via Ortega, Stanford, CA 94305, USA 2 Living Landscapes Indonesia, Jl. Parit H. Husin 2, Gg. Wisata 1, No. 11B. Pontianak, West Kalimantan 78121, Indonesia 3 Department of Anthropology, Stanford University, 450 Serra Mall Bldg 50, Stanford, CA 94305, USA 4 Daemeter Consulting, Jl. Tangkuban Perahu No.6, Bogor, Jawa Barat 16151, Indonesia 5 School of Forestry and Environmental Studies, Yale University, 195 Prospect St., New Haven, CT 06511, USA 6 Department of Environmental Science, Udayana University, Badung, Bali 80361, Indonesia 7 Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK Keywords Deforestation; degradation; Indonesia; logging; propensity score matching; REDD; remote sensing. Correspondence D. L. A. Gaveau, Woods Institute for the Environment, Stanford University, 473 Via Ortega, Stanford, CA 94305, USA. E-mail: dgaveau@yahoo.co.uk Tel: +62 852 53 992273; Fax: +16507250605 Received 18 October 2011 Accepted 2 January 2012 Editor Prof. Lian Pin Koh doi: 10.1111/j.1755-263X.2011.00220.x Abstract Several studies suggest that protected areas conserve forests because deforesta- tion rates are lower inside than outside protected area boundaries. Such bene- fits may be overestimated when deforestation rates within protected areas are contrasted with rates in lands where forest conversion is sanctioned. Here, we reexamine protected area performance by disentangling the effects of land use regulations surrounding the 110,000 km 2 protected area network in Sumatra, Indonesia. We compared 1990–2000 deforestation rates across: (1) protected areas; (2) unprotected areas sanctioned for conversion; and (3) unprotected produc- tion areas where commercial logging is permitted but conversion is not. Defor- estation rates were lower in protected areas than in conversion areas (Mean: −19.8%; 95% C.I.: −29.7—−10.0%; P < 0.001), but did not differ from pro- duction areas (Mean: −3.3%; 95% C.I.: −9.6—2.6%; P = 0.273). The measured protection impact of Sumatran protected areas differs with land use regulations governing unprotected lands used for comparisons. If these regulations are not considered, protected areas will appear increasingly effec- tive as larger unprotected forested areas are sanctioned for conversion and deforested. In the 1990s, production areas were as effective as protected areas at reducing deforestation. We discuss implications of these findings for carbon conservation. Introduction Protected areas have been the predominant biodiversity conservation approach for decades (Chape et al. 2005). An estimated 23% of the Earth’s humid tropical for- est biome is under some form of protected designation to conserve forest habitats and their biodiversity (UNEP 2007). The Convention on Biological Diversity’s 2010 target to reduce the 2002 rate of biodiversity loss en- couraged research into whether protected areas reduce deforestation (Brooks et al. 2009). To estimate the protection impact of forested protected areas, researchers have typically contrasted deforestation rates inside and outside protected area boundaries (DeFries et al. 2005; Nagendra 2008; Soares-Filho et al. 2010). Protection could be inferred effective if deforestation rates were lower in protected than in unprotected sites. But, the comparatively remote locations of many protected ar- eas often overestimated protection impact (Joppa & Pfaff 2009). Studies controlled for this “high and far” bias using matching techniques or multiple linear regressions (Pfaff & Sanchez-Azofeifa 2004; Andam et al. 2008; Gaveau 142 Conservation Letters 5 (2012) 142–148 Copyright and Photocopying: c  2012 Wiley Periodicals, Inc.