Forests are hotspots for wildlife as well as important carbon sinks, provided they are well managed. Preventing deforestation is therefore a major aim of national and international policy packages designed to conserve biodiversity and reduce greenhouse gas emissions. In the EU, the European Commission has called for action to put a halt to global deforestation within the next two decades1. It is, however, very difficult to measure the effectiveness of policies designed to reduce deforestation, as it is impossible to know how much deforestation would have occurred if a given policy had not been introduced. Similarly, it is not possible to tell if by avoiding deforestation in one location, it is simply transferred to another location instead.
Designating protected areas, such as wildlife reserves and national parks, is considered to be an effective strategy to avoid deforestation. However, in a new study, researchers in the US, Canada and Costa Rica claim that reductions in deforestation due solely to the establishment of protected areas are often overestimated. The researchers propose an improved method for measuring 'avoided deforestation' from protected areas.
The study focuses on protected areas, including nature reserves and national parks, designated in Costa Rica between 1960 and 1997. In order to estimate avoided deforestation more precisely, the researchers compared levels of deforestation between protected sites and unprotected sites with very similar characteristics. This method effectively creates a control group to which sites in the protected group are closely 'matched'. Characteristics that were matched included climate, soil type and distance to the forest edge or roads.
According to the researchers, almost one tenth of protected areas in Costa Rican forests would have been deforested by 1997 had they not been protected. But using conventional methods, the estimated area of avoided deforestation is three times larger. They suggest their method overcomes problems with previous studies, which made comparisons between protected and unprotected areas without accounting for important characteristics that might determine which sites were designated. In other words, avoided deforestation in many protected areas may not be due to protection, but to the location of a site itself.
The research could be useful in assessing the impacts of future conservation policies. A fifth of all EU territory - 850,000 square kilometres - is made up of sites designated as protected under the Natura 2000 initiative2. Clearly, it is important to understand how these sites benefit. However, deforestation is also a global problem affecting global climate change and development of this new method could be crucial to future incentive schemes whereby governments, particularly in the developing world, would be able to claim carbon credits based on avoided deforestation.