Plant Conservation on the Navajo Nation – Brief Article
The Navajo Nation encompasses 17.5 million acres (28 million hectares) of the Colorado Plateau in northeastern Arizona, northwestern New Mexico, and southeastern Utah. Its dramatic landscape ranges from desert scrub to sub-alpine conifer forests. Two major rivers border the Navajo Nation, the Colorado River to the west and the San Juan River to the north. Other major geographic features include the Little Colorado River, Navajo Mountain, Rainbow Bridge, Black Mesa, Chuska Mountains, Monument Valley, Canyon de Chelly, and Shiprock.
The Navajo Natural Heritage Program (NNHP) was established in 1984, through a cooperative agreement between the Navajo Nation and The Nature Conservancy, to collect, manage, and disseminate biological and ecological information for conservation and land use planning on the Navajo Nation. The NNHP maintains a comprehensive database of information on rare and protected plant and animal species and biological communities on the Navajo Nation.
Little botanical work had been done on the Navajo Nation prior to the NNHP compared to other regions of the United States. However, since the program was formed, its botanists have conducted research to identify and classify the Navajo Nation’s plant life and have gathered fundamental data on botanical diversity through plant collections. Over time, botanists have put together a small regional herbarium including nearly 4,000 specimens collected on reservation lands. A recently developed database listing these specimens now makes information on plant locations and collections easily accessible. Many of the specimens have been collected by staff botanists in remote and difficult to access areas of the Navajo Nation, such as the canyons of the Rainbow Plateau in the northwest corner of the reservation (bordering Lake Powell in Utah) and the Little Colorado River Gorge in Arizona. From April through October, NNHP botanists and other staff members can frequently be seen carrying heavy packs and plant presses into uncharted territories of the Navajo Nation, camping out in the rough terrain, braving inclement weather and water shortages, all to find the last stronghold of little known or seldom seen plants.
Over 1,100 plant species from 90 families are known to exist on Navajo lands. The Navajo Endangered Species List includes 29 species of plants, 6 of which are federally listed as threatened or endangered. Several species of plants are known to occur only on Navajo Nation lands, including the Copper Canyon milkvetch (Astragalus cutleri), the rare Marble Canyon milkvetch (Astragalus cremnophylax var. hevronii), and the federally listed Navajo sedge (Carex specuicola).
Once known from only two locations near Inscription House in northern Coconino County, Arizona, the Navajo sedge is now known from 23 sites ranging all the way eastward to Chinle Creek in San Juan County, Utah. Navajo sedge is very localized and is restricted to seep areas or to hanging gardens in the Navajo Sandstone formation along often inaccessible sheer cliff faces. Although these extensive surveys indicate that the Navajo sedge may not be imminently imperiled with extinction, the species continues to be threatened by water development and overgrazing at its more accessible sites.
The Copper Canyon milkvetch, a very local endemic on the Navajo Nation, is known only from a 4-mile (6.5-km) stretch between Copper Canyon and the adjacent Nokai Canyon in San Juan County, Utah, near Lake Powell. Despite extensive surveys, the range of this plant has not been extended significantly beyond these locations. The remoteness of these areas keeps threats to the species’ survival at bay for the time being.
The Marble Canyon sentry milkvetch was described in 1992 after being discovered by former NNHP botanist Bill Hevron. Three varieties are now known, and all are restricted to the limestone rims of the Grand Canyon and Marble Canyon in Coconino County, Arizona. NNHP botanists have spent a considerable amount of time walking the rim of Marble Canyon in hopes of documenting the population beyond its current range, but so far without success. The Marble Canyon milkvetch is currently considered the rarest plant known on reservation lands because of its small range and restricted habitat availability.
The Mesa Verde cactus (Sclerocactus mesae-verdae) was once known from only a few scattered populations in northwestern New Mexico and southwestern Colorado. Extensive field work has indicated that this federally listed cactus is not as restricted in its distribution within this region as previously thought. The NNHP monitors several populations of Mesa Verde cactus in the Four Corners area. One of these populations includes transplanted cacti salvaged from a road construction project. Annual monitoring began in the early 1990’s. Population data helps to determine the status of a species, to see whether a population is increasing or decreasing, and to evaluate response to natural and man-made threats such as drought, insect attacks, transplanting, and off-road vehicle use. While the Mesa Verde cactus continues to suffer habitat destruction, its potential for delisting has increased due to our new knowledge.
The rare plant list of the Navajo Nation is dynamic and continues to change as we gather new information on rare species. As time passes, we hope to be able to shed even more light on the distribution and abundance of native sensitive and rare plants of the Navajo Nation.
Daniela Roth is a Botanist with the Navajo Natural Heritage Program.
COPYRIGHT 1999 U.S. Fish & Wildlife Service
COPYRIGHT 2004 Gale Group