Examining protected area effectiveness in Sumatra: Importance of regulations governing unprotected lands

Several studies suggest that protected areas conserve forests because deforestation rates are lower inside than outside protected area boundaries. Such benefits 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 km² 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 production areas where commercial logging is permitted but conversion is not. Deforestation 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 production 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 effective 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.