Exotic Invasives Threaten Grassland Ecosystems

Home to a vast assemblage of plant species, the grasslands of the Santa Cruz Mountains are one of the most diverse, species-rich, and unfortunately, also one of the most endangered ecosystems in the United States.

Prior to the 18th century, California's grasslands consisted primarily of perennial grasses, but with the introduction of non-native plants and animals brought by European settlers, the plant composition changed dramatically. Exotic annuals that were introduced spread rapidly, out-competing native plants for light, nutrients, and water. The proliferation of exotic vegetation poses a serious threat to the unique biodiversity of these grassland ecosystems. By some estimates, exotic vegetation accounts for nearly 80% of the vegetation cover within California grasslands today.

District lands encompass approximately 5,300 acres of grasslands. The largest sections stretch from the crest of the Santa Cruz Mountains along the Skyline Ridge out towards the the coast and encompass Big Dipper Ranch, Driscoll Ranch, and the former McDonald Ranch at La Honda Creek Open Space Preserve.

Grazing as a Resource Management Tool

As part of the District's mission to protect the diversity and integrity of natural resources for their value to the environment and to people, the District's grazing policy helps restore native perennial grasses and wildflowers by taking advantage of the annuals' life cycles and the appetites of cattle. "Having cattle eat the annual grasses early will allow for native grasses and wildflowers to germinate, " explained Kirk Lenington, Senior Resource Planner for the District.

In addition to the management of non-native grasses, grazing offers other benefits: fire fuel reduction, which minimizes the risk of wildfire, and support for the local agricultural economy.

District Grazing Policy

In January 2007, the Board of Directors tentatively adopted amendments to the District’s Resource Management Policy, including a new chapter on Grazing Management. To develop the draft Grazing Management Policy, District staff met with and consulted a number of agencies and organizations, including the San Mateo County Farm Bureau, the U.S. Department of Agriculture, the San Mateo County Agriculture Advisory Committee, and the San Mateo Resource Conservation District.

Once the comprehensive review of all District Resource Management Policies is complete, the Policies will be returned to the Board for formal adoption.