Amazonian nature reserves : an analysis of the defensibility status of existing conservation units and design criteria for the future

Without effective implementation, tropical reserves cannot count on in situ enforcement, and consequently are subject to a wide range of invasive threats. Weak institutional structures are aggravated by reserve designs which facilitate rather than discourage unlawful human activities. Here we begin with the assumptions of severe financial and institutional constraints and then consider the current status of forest reserves in lowland Amazonia. We ask how the criteria by which reserves are delimited may affect the efficiency with which the contained areas can be defended under these assumptions. In a GIS analysis, we find that 40% to 100% of the area of all existing nature reserves in Brazilian Amazonia is directly accessible via navigable rivers and/or functional roads. Such access greatly facilitates the illegal offtake and conversion of forest resources in a region where each guard is responsible for protecting an area larger than the State of Delaware. Cost effective defense of large areas can be achieved through appropriate delimitation of reserves along watershed divides and by efficient deployment of limited infrastructure and personnel. Given current and probable future levels of financial resources allocated to reserve maintenance in Amazonia, any new nature reserves in this region should be designed and sited so as to maximize their defensibility. Siting considerations based on biological criteria, such as presumed centers of diversity and endemism, should be complemented by defensibility criteria. (Author abstract)