I Contributed Papers Amazonian Nature Reserves: An Analysis of the Defensibility Status of Existing Conservation Units and Design Criteria for the Future CARLOS A. PERES* AND JOHN W. TERBORGH Center for Tropical Conservation, Duke University, 3705-C Erwin Road, Durham, NC 27705, U.SA. AbstracU Many tropical nature resenms are woefully understaffed or exist only on paper. Without effective implementation, tropical reserves cannot count on in situ enforcement and consequently are subject to a wide range of invasive threat~ Weak institutional structures are aggravated by reserve designs that facilitate rather than discourage unlawful human activitie£ Taking into account severe financial and institutional constrain~ we 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 are defended In a GIS analysi~ we found that 40 to 100% of the area of all existing nature reserves in Brazilian Amazonia are directly accessible via navigable rivers and/or functional road& Such access greatly facilitates the illegal harvest 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 situated so that their defensi- bility is maximized Defensibility criteria should complement site considerations based on biological crite- ria, such as presumed centers of diversity and endemisn~ gas Reservas Naturales Amaz6nicas: un anfilisis del estado relativo de protecci6n de las unidades de conservaci6n existentes y del criterio de disefio para el futuro Resumen: Muchas reservas naturales tropicales se encuentran desastrosamente atendidas o existen s6la- mente en papele£ Sin una implementaci6n efectiv~ las reservas tropicales no pueden contar con una implementacidn in situ de la ley yen consecuencla estan sujetas a un amplio espectro de amenazas inva- sora~ Las estructuras institucionales ddbiles seven agravadas por disetios de reservas que facilitan mds que desalientan las actividades humanas fuera de la ley. En este estudio, consideramos el estado actual de las reservas de bosques en las tierras bajas de la Amazoni~ tomando en cuenta las severas restricciones finan- cieras e instttucionale~ Nos preguntamos c6mo el criterio pot el cual las reservas son delimitadas puede afectar la eficiencia con la cual ias dreas contenidas son defendidas. A tratMs de un andlisis de SIG, encon. tramos que entre un 40 y un 100% del drea de todas ias reservas naturales extstentes en ia Amazonia Brasilet~a resulta directamente accesible pot medio de rios navegables y/o rutas funcionaleg Este tipo de acceso facilita la recolecci6n ilegal y ia conversi6n de recursos forestales en una regi6n ddnde cada guardla es responsable de proteger un drea mayor que el Estado de Delaware. Una defensa de grandes drea~ eficiente desde un punto de vista de costo~ se puede lograr a travds de una delimitaci6n adecuada de las reservas a lo largo de las lineas divisorias de aguas y mediante un empleo eficiente de los limitados recursos de infraestructura y personal Dados los niveles de los recursos financieros presentes y probablemente futuro~ * Current address: Departamento de Ecologia Gera~ Instituto de Bioct&ncias Universidade de Sd~ Paulo, Caixa Postal 11.461, Sdio Paul~ ~P. 05422-970, Brazil Paper submitted July 26, 1993; revised manuscript accepted March 16, 1994. 34 Conservation Biology,Pages 54-46 Volume 9, No, 1, February 1995