An ecology-based method for defining priorities for large mammal conservation: the tiger as case study

Abstract

The disappearance of large vertebrates in the tropical belt may be the next biological insult of the global extinction crisis. Large predators and their prey are at particular risk in Asia, where they are threatened by poaching and habitat loss. To facilitate the best use of limited conservation resources, we created an objective, ecology-based method for identifying priority areas for conservation that incorporates both habitat representation and landscape-level features. Using tigers as an example, our method captures the range of ecological habitats where they occur, accounting for ecological, demographic, genetic, and behavioral differences. Our analysis is hierarchical. We divided the tiger range into distinct bioregions and identified tiger habitat types within each. We then delineated tiger conservation units throughout the bioregions and ranked the units based on habitat integrity, poaching pressure, and tiger population trends. To maintain representation of tiger populations and their ecology in the different tiger habitats, we made comparisons only among tiger conservation units from the same tiger habitat types nested within the same bioregion. We identified 159 tiger conservation units in three bioregions-the Indian subcontinent, Indochina, and Southeast Asia. We ranked the units in three categories that reflect the probability of long-term persistence of tiger populations ( highest in level I units). Twenty-five tiger conservation units were classified as level I, 21 as level II, and 97 as level III. An additional 16 tiger conservation units for which little information is available were identified for immediate surveys. Levels I , II, and those identified for immediate surveys are the priority areas for immediate funding and for a regional tiger conservation strategy. One feature emerging from the study showed that protected areas cover only small areas of tiger conservation units. If the long-term prospects for tiger conservation are to improve, poaching must be stopped and protected areas increased in number, linked, and buffered by natural habitats. To enhance landscape integrity, the priority tiger conservation units that straddle international borders should be managed as transboundary reserves, giving tiger conservation a stronger regional structure. Like tigers, populations of other wide-ranging mammalian carnivores and large herbivores also are declining due to poaching and loss of habitat. The method we present for tigers can be adapted readily to improve conservation strategies for these species as well.