In Southern California, many of the riparian corridors, meadows, and ponds have been overrun by Tamarisk (Tamarix). Not only does this affect the hydrology in these areas, but it out competes native vegetation causing a thick, almost impenetrable barrier that impedes wildlife movement. This issue has been a major focal point of many state and federal agencies in the Southwest Desert Region of the United States.
In 2017, CDA partnered with the Wildlife Conservation Board (WCB) and the California Department of Fish and Wildlife (CDFW) to combat invasive species Tamarisk on the San Felipe Valley Wildlife Area (SFVWA). This is a state-owned property located in eastern San Diego County with the primary focus of deer and deer habitat. SFVWA consists of approximately 17,800 acres acquired and managed by CDFW for the protection and enhancement of mule deer and desert riparian habitat. This property was purchased with the intent of linking them with adjacent Bureau of Land Management (BLM) and California State Park lands.
There have been two previous Tamarisk removal projects on the SFVWA dating back to 2006. Both of these projects have been 100% successful in the removal of the invasive species. This current effort is aimed at completely eradicating the invasive species throughout the remainder of the property.
Many riparian systems within the western Colorado Desert are infested with invasive and non-native plant species such as salt cedar, which can pose a major threat to these sensitive desert habitats. Since salt cedar has the potential to be so damaging to riparian and marsh habitats, it is therefore a species of particular concern for property owners and land managers in this region. Like many invasive species, salt cedar has no natural limiting factors outside its native range. Once established, it can outcompete native plant species and form dense, monotypic stands. Wildlife habitat quality is significantly degraded by these changes in vegetation structure and, in some cases, by the creation of physical barriers that can prevent wildlife access to water sources. Additionally, salt cedar is a prodigious water user that can further reduce water availability for native plant and animal species.
Additional concerns about salt cedar are related to changes in natural water flow patterns and soil chemistry. Dense stands create large amounts of excess biomass that can potentially impede water levels and heighten flood risk during periods of high-water flow. Increased erosion, streambank scouring and altered hydrology are frequently the result of dense infestations. Salt cedar is reported to accumulate high salt concentrations in its foliage. Subsequent leaf drop of these high salt content leaves may increase soil salinity and discourage the growth of other, more desirable plant species at infested sites.
Salt cedar removal enhances and protects biodiversity, watershed health and special status species and also reducing the risk of wildfire to the nearby communities of Julian and Shelter Valley. San Felipe Creek has long served as a primary stopover for migrating birds in the arid Colorado Desert and is an important resource for state and federally-listed species such as peninsular bighorn sheep, least Bell’s vireo, southwestern willow flycatcher, and yellow-billed cuckoo.
Successful completion of this project on the SFVWA and in the San Felipe Creek watershed would fulfill objectives of the multi-agency MOU regarding conservation and management of desert watersheds in San Diego and Imperial Counties. Restoration of natural conditions along this valuable riparian system, as well as the protection of rare, threatened, endangered, and special status species, are prime concerns of the state and federal land management agencies managing lands in the region.
Initial treatment of the 418 acres of Tamarisk in the SFVWA began during the fall of 2018 and was completed in February of 2019. The removal consisted of hand cutting and chipping all tamarisk and following up with an herbicide on the stumps to prevent new growth. Overall, the project has been 100% successful and has already made an immediate impact to the San Felipe Creek during the rainy season this past winter.
Over the next three years, CDA and CDFW will be monitoring and treating the 418 acres where the Tamarisk removal took place to ensure the success of the project. In the meantime, several water projects both on the SFVWA and in the Colorado Desert have been identified and have secured funding to implement during 2019 and in the spring of 2020.
