Management
Status & Threats
Agriculture, invasion by exotic species, development and other human-related activities have reduced California native grasslands by 99%. Coastal prairies have fared only slightly better than other grassland types: only 10% of the native coastal prairie communities remain.
Over 24% of coastal prairies in California north of San Francisco has been urbanized, the most of any major plant community in the United States.
Altered fire regimes, cultivation, over grazing and invasive annual grasses are major contributors to the conversion of native perennial grasslands to exotic annual-dominated grasslands and their continued persistence.
From 57% to 80% of California’s grasslands are privately owned and managed by ranchers:
- Overgrazing can significantly reduce root growth reducing the flow of carbon to the root system.
- Undergrazing can favor non-native species. Grazing removal efforts that were previously thought to increase perennial grasses resulted in grasslands dominated by non-native annuals.
Presently, the mean fire return interval in prairies is 20-30 years, an increase from 1-15 years interval during the lightening, aboriginal, and Spanish periods.
In the absence of disturbances, such as fire and grazing, a thick layer of plant litter accumulates in grasslands and can reduce species diversity through shading, physically interfering with plant growth, hindering germination cues, providing shelter for invertebrate herbivores and seed predators and encouraging pathogens.
Nitrogen inputs from human activities into ecosystems in the United States doubled between 1961 and 1997. Nitrogen deposition from auto exhaust has been linked to the increase of non-native grasses in some areas of the San Francisco Bay area.
Restoration
Prescribing appropriate levels and types of disturbance is one of the biggest challenges to managers interested in restoring and preserving coastal prairie.
To begin the process of designing a managment or restoration plan:
- Dispel common myths, such as, “restoring historic disturbance regimes will restore coastal prairie,” “researchers have figured all this stuff out,” “what works this year will work next year” “fire is fire and grazing is grazing.”
- Set a clear goal.
- Identify the grasses and grassland forbs.
- Target the worst species (the ones that crowd out the native species) and best species (natives that grow well at your site).
- Get to know your target species. In particular, find out how long they live (annual or perennial), when they set seed, how long seeds last in the soil, types of vegetative growth, and root characteristics.
- Use the characteristics of your target species to prescribe treatments that reduce the unwanted species and increase the desired species.