ABSTRACT:  In 1990 the U.S. Fish and Wildlife Service (USFWS) listed the desert tortoise, Gopherus agassizii, as “Threatened” over 30% of its geographic range and shortly thereafter selected a team to develop a plan for its recovery.  The team developed a hypothesis-driven recovery plan, using population viability analyses and principles of reserve design.  The Desert Tortoise (Mojave Population) Recovery Plan is designed to achieve a 50% probability of survival for the tortoise for 500 years.
        Drawing from concepts outlined in the federal Endangered Species Act, the recovery team used a strategy of protecting evolutionarily significant population units and their associated ecosystems.  The six population units, called “recovery units,” were identified using published and unpublished data on genetic variability, morphology, and behavior patterns of populations as well as ecosystem types.  Boundaries of the six units closely approximate major ecosystem boundaries in the Mojave and Colorado deserts.  The goal is to reach a target (where possible) of 50,000 breeding adult tortoises for each recovery unit.
        Within the recovery units, the recovery team recommended the establishment of 14 reserves or Desert Wildlife Management Areas (DWMAs), ranging from 415 to 3,367 km² (with one exception, the Virgin River DWMA, which was very small).  The USFWS followed by designating 26,087 km² as federally protected “Critical Habitat” in 1994.  Additional habitat is also protected within Joshua Tree National Park (est. 2,574 km² and within the existing boundaries of the Desert Tortoise Research Natural Area (est. 100 km²).
        The recovery team attributed declines in tortoise populations to the result of human activities.  To reduce and ultimately eliminate many sources of mortality that are driving the desert tortoise toward extinction, they recommended prohibition of several activities in the reserves.  Within each DWMA, they also recommended that <10% of habitat be designated as “experimental management areas,” where intrusive and experimental research can occur.
        Governments at the federal, state, county, and city levels have begun to implement the Recovery Plan through development of regional land-use plans (habitat conservation plans, coordinated resource plans, and multi-species plans).  While tortoise recovery considerations are the driving force for land-use planning, agencies are taking a more comprehensive ecosystems approach.  If implementation of the Recovery Plan and land-use plans are successful, the reserve system for the desert tortoise will not only conserve its genetic diversity, but also the biodiversity of several major ecosystems in the Mojave and Colorado deserts.