"Our results support the notion that ranches are important for protecting biodiversity and suggest that future conservation efforts may require less reliance on reserves and a greater focus on private lands," say Jeremy Maestas, who did this work while at Colorado State University in Fort Collins and is now at the U.S. Natural Resource Conservation Service in Provo, Utah; Richard Knight of Colorado State University in Fort Collins; and Wendell Gilgert of the U.S. Natural Resource Conservation Service in Fort Collins in the October issue of Conservation Biology.
About 30 million acres of U.S. ranch and farmland were converted to rural residential developments during the 1990s. This trend has increased the popularity of preserving ranches with conservation easements, which restrict development but often allow livestock production.
So far more than 1,200 land trusts have used conservation easements to preserve about 2.5 million acres of land in the U.S. However, this approach assumes that preserving ranches helps protect biodiversity, and some conservationists argue that ranching and maintaining biodiversity are incompatible in the West.
To see if ranches do help protect biodiversity in the rural West, Maestas and his colleagues surveyed birds and plants in cattle ranches, rural residential developments and nature reserves near Fort Collins, Colorado. The average lot size in the rural developments was 40 acres.
The researchers' findings support the assumption that preserving ranches helps protect biodiversity in the West. Ranches had higher densities of the ground- and shrub-nesting birds that are typical of the local native shrub/grassland habitat, such as green-tailed towhees and vesper sparrows. In contrast, rural developments had higher densities of nest predators, such as the black-billed magpie, and of birds that are usually uncommon to the area, such as Bullock's oriole, a tree-nester that is presumably attracted by the landscaping trees.
Moreover, ranches had more native plant species and fewer non-native plant species than rural developments and reserves. Altogether the ranches had only half as many non-native plant species as the rural developments, and only two-thirds as many as the reserves (11 vs. 23 and 17, respectively). In addition, the coverage of cheatgrass, the most common non-native plant, was lower on ranches than on rural developments or reserves (14%, 18% and 22%, respectively).
"Ranches can be more effective than reserves at maintaining native biotic communities," say Maestas and his colleagues. Reserves may be inadequate because most are in harsher environments with higher elevations and poorer soil. Moreover, the reserves studied have extensive trail systems that could facilitate the spread of non-native plants.
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