Status and Trends of Plants

East Tavaputs Plateau, Utah. Photo © Ray Wheeler.

The states of New Mexico and Arizona may have the greatest diversity of vascular plant species in the continental United States. New Mexico is estimated to have about 3,900 and Arizona about 3,370 species of flowering plants and ferns. Endemism is high among plants on the Colorado Plateau in Utah, but less high in more southern areas: about 5% of Arizona plant species are endemic (46 species on the Colorado Plateau), and less than 4% in New Mexico (24 are cacti, mostly in the desert regions). The number of nonindigenous or introduced species is also high; Utah has at least 580 introduced species sharing space with about 2,500 species of indigenous vascular plants.

The Plateau has some of the highest proportions of globally rare native plants in the country, about 15% of the total taxa, yet northern portions of the Plateau are some of the mostly poorly studied areas for vascular plants. The moss flora of the region, for example, is one of the least known in the United States, and our knowledge of liverworts and hornworts in New Mexico, Arizona and surrounding regions is the poorest in the country.

The list of threatened and endangered plants on the Colorado Plateau is large. Arizona, New Mexico and Utah each list from 50 to 140 taxa of plants as sensitive. These include cacti, wild buckwheats, prickly poppies, mil-vetches, paintbrushes, penstemons, sagebrushes, and others. The sunflower, pea, cactus and figwort families account for more than half of the species of special concern in New Mexico. For a list of threatened and endangered species on the Colorado Plateau, click here.

Land uses which have contributed to the threats to sensitive plants include grazing, fire suppression, road building, urbanization, and water diversion and development. Some cacti and plants with showy flowers have been threatened by overcollecting for the horticultural trade. As knowledge about the use of medicinal herbs by Native Americans has spread, populations of some of these plants have also suffered from overcollecting and poaching on public lands.

Albee, B. J., Shultz, L. M. and Goodrich, S., editors. 1988. Atlas of the vascular plants of Utah. Occasional Publication 7. Utah Museum of Natural History, Salt Lake City.

Brown, D. E. 1994. Biotic communities of the Southwestern United States and northwestern Mexico. University of Utah Press, Salt Lake City, 342 pp.

Dick-Peddie, W. A. 1993. New Mexico vegetation: Past, present and future. University of New Mexico Press, Albuquerque, 244 pp.

Edwards, T. C. 1995. Protection status of vegetation cover types in Utah. Pp. 463-464 In: LaRoe, E. T., Farris, G. S., Puckett, C. E., Doran, P. D. and Mac, M. J., editors. Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.

Flather, C. H., Joyce, L. A. and Bloomgarden, C. A. 1994. Species endangerment patterns in the United States. General Technical Report RM-241. U.S. Forest Service, 42 pp.

Grossman, D. H. and Goodin, K. L. 1995. Rare terrestrial ecological communities of the United States. Pp. 218-221 In: LaRoe, E. T., Farris, G. S., Puckett, C. E., Doran, P. D. and Mac, M. J., editors. Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.

Kearney, T. H. and Peebles, R. H. 1960. Arizona flora. 2nd edition with supplement. University of California Press, Berkeley and Los Angeles, 1085 pp.

Mac, M. J., Opler, P. A., Haecker, C. E. P. and Doran, P. D., editors. 1998. Status and trends of the Nation's biological resources. U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, 986 pp. Also available at http://biology.usgs.gov/s+t/SNT/index.htm.

Martin, W. C. and Hutchins, C. R. 1980. A flora of New Mexico. Volume 1. J. Cramer, Hirschberg, Germany, 1276 pp.

Martin, W. C. and Hutchins, C. R. 1981. A flora of New Mexico. Volume 2. J. Cramer, Hirschberg, Germany, 1315 pp.

Morin, N. 1995. Vascular plants of the United States. In: LaRoe, E. T., Farris, G. S., Puckett, C. E., Doran, P. D. and Mac, M. J., editors. Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.

Morse, L. E., Kartesz, J. T. and Kutner, L. S. 1995. Native vascular plants. Pp. 205-209 In: LaRoe, E. T., Farris, G. S., Puckett, C. E., Doran, P. D. and Mac, M. J., editors. Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.

Schaack, C. G. 1970. A flora of the arctic-alpine vascular plants of the San Francisco Mountains, Arizona. M.S. Thesis. Northern Arizona University, 107 pp.

Stromberg, J. C. and Chew, M. K. 1997. Herbaceous exotics in Arizona's riparian ecosystems. Desert Plants 13: 11.

Tuhy, J. 1995. Endangered plants of the Moab area. Canyon Legacy 23: 11.

Welsh, S. L., Atwood, N. D., Goodrich, S. and Higgins, L. C., editors. 1987. A Utah Flora. Great Basin Naturalist Memoirs, Volume 9, 894 pp.

Whittemore, A. and Allen, B. 1995. Floristic inventories of U.S. bryophytes. Pp. 198-200 In: LaRoe, E. T., Farris, G. S., Puckett, C. E., Doran, P. D. and Mac, M. J., editors. Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.