Redlands, CA 92374
Phone: (909) 799-7407
Invasive Species Removal Projects
Inland Empire Resource Conservation District's Invasive Species Removal Projects.
Giant cane is a species of perennial grass found present throughout the Santa Ana watershed, located primarily within or adjacent to riparian systems, but also present in upland habitats. The origins of the Arundo donax plant in southern California has not been precisely pinpointed; however, it is widely thought to have been introduced in the early 19th century into the areas surrounding the Los Angeles River, and has since spread throughout southern California and north in various levels of habitat infestation depending on climactic conditions. Arundo donax grows at an extremely rapid rate of up to 4 centimeters per day, in clumped patches of long woody stems that experience semi-dormancy in winter months and/or periods of drought. In North America it spreads primarily through plant fragments that break off and reestablish downstream.
This plant causes a myriad of problems for native habitats and dependent environs including compromised water quality and quantity, elimination of existing and prevention of establishment of new populations of native plants and increased risk of fire and flood. This reduction in native plant population presence reduces opportunities for foraging and shelter for wildlife and can raise temperature of water in areas that would otherwise be shaded by the overhang of native tall shrubs and trees. The reduced habitat functionality of riparian systems due to the spread of Arundo donax continues to be a threat to survival of already marginalized species including the least Bell’s vireo (Vireo bellii pusillus) and the southwestern willow flycatcher (Empidonax traillii extimus).The IERCD works to combat the presence of Arundo donax in its section of the Santa Ana River watershed through a variety of vegetation management projects performed over various regions of its service area. Detailed summaries of IERCD-led large-scale removals with follow-up maintenance/monitoring of this highly invasive plant can be found in the “Projects” section of this website.
The appearance of this plant varies according to age, presenting itself first as a perennial shrub and eventually becoming a woody tall shrub capable of growing to 15 feet tall. Castorbean was introduced from warmer regions of Asia as both an ornamental and as a former agricultural crop, and escaped into wildlands via seeds spreading through humans and animals. It is found most often adjacent to active/former agricultural fields and near roads and railroad tracks, and in warmer and wetter climates with less frequent periods of drought or excessive cold. Its beans are toxic to many species including humans, horses, cattle, cats, and dogs. In addition to its toxicity, castorbean is also quick to germinate and produce plants following fire, often displacing the functional native habitats previously in existence. This reduction in native habitat, as with other species of invasives, reduces overall foraging and shelter opportunities for area wildlife and also negative impacts soil stability and health.
This species was brought into southern California from China, both as an ornamental and through railroad workers, and is a tree capable of reaching heights of 65 feet. As with other exotic plants used as ornamentals, it has escaped cultivation and become prolific throughout the state, primarily due to its spread through seed and through root sprouting. Tree of heaven is particularly prolific due to intensive seed production and tolerance of compromised air quality, allowing it to grow in locations inhospitable to native plants. It is most dangerous to native riparian habitat health, where it displaces shrubs and trees providing shelter and food support for species of area wildlife.The IERCD has included tree of heaven as a species targeted for removal in invasive management projects since 2004. Additional information on tree of heaven eradication efforts in the IERCD service area can be found in the “Projects” section.
In California, there are four different species of non-native Tamarisk plants, all of which are classified as tall shrubs/short trees, capping out at 26 feet tall. They are all in California as a result of transport here for a variety of uses including as ornamentals, for windbreaks, and for erosion control. They have escaped cultivation through seed dispersal as well as migration of plant fragments and now inhabit disturbed sites, burned areas, and riparian habitat. Their leaves contain salt glands, resulting in increasingly saline soils surrounding them, preventing establishment of functional, valuable riparian species. Tamarisk shrubs and trees cause multiple problems in wildland areas, including increased flood risk due to infliction of changes on linear riparian systems in addition to crowding out of native species and permanent changes to soil composition.
Multiple eradication efforts are underway in southern California, and the IERCD has historically and currently participated in Tamarisk control projects in its service area. More information is provided in the “projects” section of the website.
There are several species of problematic low-growing invasive plants within the IERCD’s service area, including the seemingly inexhaustible perennial pepperweed. This shrub is thought to have been introduced into California in the 1930s via agricultural seed contamination and theorized to have spread as a result of hay bales distributed for use in erosion control. It can tolerate a variety of soil moisture and composition conditions, and develops a considerable root system contributing to its survival and spread. The most threatening aspect of perennial pepperweed is its advancement as a monoculture throughout the state, occupying disturbed areas previously populated with functional native plants.
The IERCD works to eradicate perennial pepperweed populations throughout its service area, most recently in partnership with the Riverside Land Conservancy over the Cienega Property located in the San Timoteo Canyon region of unincorporated Riverside County. More information on perennial pepperweed removal is located in the “Projects” section of the website.
As with the aforementioned perennial pepperweed, yellow starthistle is thought to have entered California first through seed contamination, then spread through movement of humans, animals, and transport of hay and seed. It is an annual invasive weed easily identified by its spiny yellow flowerheads, and has increased its statewide presence from 1 million acres in 1950 to over 15 million acres today. It occupies a variety of habitats, especially those adjacent to disturbed areas found alongside transportation corridors and agricultural areas. The most damaging effects of this species seem to be depletion of soil moisture in addition to transition of wildland areas from native coastal sage scrub habitats to monocultures of yellow starthistle. The conversion of valuable native habitat reduces overall availability of food and foraging opportunities for dependent wildlife.
This project began in 2002, and involved the removal of approximately three full acres of invasive species including giant cane (Arundo donax), castor bean (Ricinus communis), and tamarisk (Tamarix spp.) from a 22.5-acre eradication site. Mechanized methods of removal were employed for this effort, with follow-up spraying and monitoring occurring quarterly until removal was complete. Currently, the project site is 99% eradicated and is monitored on a bi-annual basis by District staff to ensure continual control of invasives.
The East Twin Creek removal project was initiated in 2002 by the East Valley Resource Conservation District, prior to its consolidation with the Inland Empire West Resource Conservation District which resulted in what is now the Inland Empire Resource Conservation District. The project site is located in the foothills of the San Bernardino Mountains, beginning where East Twin Creek is coincident with Coldwater and Strawberry Canyons, downstream for a total site length of approximately five miles. The total project site size is 100 acres, of which approximately 25 were infested with giant cane (Arundo donax), castor bean (Ricinus communis), and saltcedar (Tamarisk spp.). This was especially problematic as the majority of the acreage was located directly adjacent to East Twin Creek, a tributary of the Santa Ana River. The extraordinary ability of giant cane to colonize locations via hydrologic conduction of plant material made this project a priority, in order to eradicate local populations as well as to prevent further growth downstream.
Since the initial treatment, this site has been maintained annually to prevent re-infestation of giant cane, as well as to encourage the re-colonization of the site by native species of vegetation. These efforts have been very successful, as the presence of giant cane is less than 1% of the acreage at East Twin Creek, and the appearance of native species of willow (Salix spp.), cottonwood trees (Populous fremontii), and mulefat shrubs (Baccharis salicifolia) has been consistent in each year post-initial treatment. This careful bi-annual monitoring work which has resulted in restoration of the East Twin Creek site by valuable, native wildlife-sustaining species of vegetation will continue in perpetuity.
The giant cane removal effort involved approximately ½ acre of vegetation located within the challenging terrain of the Preserve. The initial eradication was completed In November of 2004, with a five-year spray contract commencing in the spring of 2005. Currently, the site is 99% eradicated, and annual visits by District staff will continue in perpetuity to ensure minimal re-growth of invasive species.
When the project began, the IERCD then known as the East Valley RCD, contracted for the removal of 30 acres of stands of 75-100% pure giant cane as well as smaller stands of castor bean scattered throughout the site. The original agreement was executed in January of 2004, and involved the initial physical removal of the invasive biomass, followed by five years of maintenance and monitoring to ensure minimal re-growth of target species. The agreement terminated in January of 2009, and the final walk-through of the site took place on May 29th, 2009; at this final meeting, the IERCD certified that the contracted removal agency had been successful in eradicating all but <1% of the targeted invasives. The site will continue to be monitored periodically by the IERCD, and will be turned over to staff of the Santa Ana Watershed Association in January of 2011.
The initial removal was completed in July of 2001, with five years of herbicide treatment and follow-up monitoring required, resulting in project completion in August of 2006. Currently, the IERCD field ecologist monitors this site, which has experienced very little re-growth of giant cane, but has experienced re-invasion by the opportunistic tree tobacco (Nicotiana glauca). Removal of tree tobacco is slated for late fall of 2010; afterwards, annual monitoring of the site should be sufficient to ensure continued control of invasive species.
The main justification for treatment of invasives at the site was its ultimate connectivity to a drainage moving first through citrus groves in the City of Redlands, and ultimately emptying directly into the Santa Ana River. This project was made possible through funding provided by Federal dollars received by the East Valley RCD, now the IERCD, which were earmarked for projects involving the documentation and removal of invasive species in the Santa Ana Watershed.
The staff of the Inland Empire Resource Conservation District documented the presence of invasive species including giant cane at both of these sites, both of which are tributaries or sub-tributaries of the Santa Ana River, in the summer of 2009. The contract for removal was executed in the fall of 2009, and targeted giant cane (Arundo donax), resulting in all stalks being removed before the end of the year. Now that the existing biomass has been removed, the maintenance and monitoring portion of the project will begin, with termination of agreements scheduled for fall of 2010. Once the site is declared successful, IERCD staff will take over the responsibility of actively monitoring for re-growth, and eradicating such vegetation should it appear.
The initial removal began in March of 2003, with an additional 185-acres added onto the original project area in order to maximize the invasive species removed. The project area underwent mechanical removal of invasive species biomass, followed by five years of herbicide treatment to prevent re-growth. The spray contract was set to expire in March of 2009, but was renewed by the Inland Empire RCD, to include all original project acreage. In addition to giant cane (Arundo donax), the 2009 Norco Bluffs/Burn contract targets additional invasive vegetation including tamarisk (Tamarix spp.), perennial pepperweed (Lepidium latifolium), tree of heaven (Ailanthus altissima), tree tobacco (Nicotiana glauca) and castor bean (Ricinus communis). Spraying of wetlands-approved salt-based herbicides commenced in the fall of 2009 and will terminate in fall 2010, with five years of monitoring and maintenance planned for the site.
This project was conceptualized in cooperation with SAWA, the non-profit agency with which the IERCD often collaborates on such efforts. The actual project area represented less than one acre in size, and consisted of giant cane (Arundo donax), tamarisk (Tamarix spp.), and castor bean (Ricinus communis). Removal of these species was complicated by the presence of native vegetation intermixed with the invasives; for this reason, the contractor selected for the job employed methods of hand-removal of all target plants. The contract began on October 23rd, 2002 and expired on the same day in 2007. Following initial removal, five years of maintenance and monitoring were completed within the project area.
Currently, the IERCD field ecologist is monitoring the site and treating any re-growth detected in and around the project area. The need to continue to maintain this site as a location devoid of invasive species is due to its location adjacent to the main linear drainage of this watershed, the Santa Ana River. Re-growth is currently less than 1% and it is projected that annual monitoring and spot treatment will maintain this number in perpetuity.
The initial removal work began in February of 2006, using heavy mechanized equipment with feacon grinder attachments for mulching the cut biomass. The work temporarily ceased in April of 2006 when the endangered least Bell’s vireo (Vireo bellii pusillus) was located within the project boundaries. Biologists employed by the Santa Ana Watershed Association spent a significant amount of annual staff time monitoring regional removal projects, in order to ensure absence of endangered and/or threatened species. Removal resumed in September of 2007, which is the month that marks the official end of the nesting seasons for vireo, and continued until completion in December 2007. The individual population stability of wildlife such as the least Bell’s vireo is one of the goals set in removal of invasive vegetation in the region; therefore any activities considered harmful, even those done in conjunction with an overall beneficial project, are immediately stopped and do not resume until absence of said species can once again be determined.
Since the end of the initial removal in 2007, an outside contractor has monitored the area and completed herbicide treatments to any visible re-growth on a monthly basis. Currently, the site is approximately 70% controlled, and the District anticipates this will reach 95% by the end of the fifth year of spray treatment. The herbicide treatment will continue until 2012, at which point the presence of invasives on the project site is targeted to be less than 5%. At that point, IERCD staff will take over monitoring and occasional treatment of re-growth on a quarterly basis. The prevention of re-growth of aggressive invasive species is critical for a project area of such considerable size, as its absence allows for restoration of large parcel of public land that will be preserved in perpetuity.
The initial removal of invasive biomass was completed in June of 2003, despite being repeatedly delayed due to the presence of two sensitive regional species, the Santa Ana River woolly star (Eriastrum densifolium sanctorum) and the San Bernardino kangaroo rat (Dipodomys merriami parvus). The existence of these species at the project site required full-time biological monitoring, which complicated the timeline of the removal; however, ultimately 86-acres of invasives were removed. Following the cutting and mulching of biomass, the area was treated with an Environmental Protection Agency-approved herbicide using a foliar spray application technique. This is standard in all removal projects, and is done in order to discourage re-growth of the target species.
In November of 2009, the IERCD worked with the United States Forest Service (USFS) to conduct the removal of approximately one full acre of tree of heaven, interspersed among three acres of habitat. The District and crews working on behalf of the USFS employed the “cut and daub” technique for removal of this invasive tree, a method involving the felling of trees, followed immediately by hand application of a wetlands-approved herbicide. This method is widely used on land classified as USFS-patrolled property, as it is the removal method least likely to contaminate adjacent stands of natives during treatment of invasive species. Following the initial treatment, the District conducted one follow-up visit to gauge site success, and will continue to actively monitor beginning in September of 2010, at the end of the official nesting season.
The IERCD also participated with the Forest Service in a removal project located in the Applewhite Picnic Area, also in the Lytle Creek watershed. In this location, tree of heaven was also targeted; however, its small size rendered it inappropriate for treatment using the cut-and-daub method employed at the adjacent campground project. Instead, IERCD staff along with USFS staff used foliar spray application of wetlands-approved herbicide. Currently, this site is only 85% under control, and therefore will continue to be monitored and treated by IERCD staff to ensure total control of invasive plants at the site.
In March of 2010, the physical removal began, after determining absence of breeding birds including the least Bell’s vireo. A salt-based herbicide approved by the Environmental Protection Agency was applied to all affected areas, by IERCD staff in conjunction with removal technicians from the Santa Ana Watershed Association (SAWA). SAWA equipment including a Polaris vehicle was used in these treatment applications, allowing employees to reach larger areas than previously allowed during the traditional method of application on foot. Following this initial removal, there will be additional treatment, follow-up maintenance and monitoring for a minimum of two years at the site.
Upon project completion, annual monitoring will continue in perpetuity to ensure minimal re-growth. The elimination of local populations of this species will assist with the desired regional extirpation required to prevent the widespread presence of this plant as it exists in northern California.
Another recent addition is French broom (Genista monspessulana), a rapidly spreading non-native shrub found in multiple locations within California, one of two locations worldwide where it is especially problematic. The ability of French broom to produce copious amounts of seed, to colonize disturbed areas, and to re-sprout after traumatic conditions such as freezing and cutting has allowed it to thrive and spread. This hardiness is also what is most dangerous about broom, as it readily out-competes natives and is difficult to eradicate. The importance of early control of species such as French broom cannot be overstated; if allowed to spread, it becomes extremely costly to treat, and causes considerable damage to the native habitats it invades.
In 2008, the District was notified by a local professor of a population situated in a regional park in the City of Yucaipa and County of San Bernardino. After an initial inspection by the Field Ecologist, the population was then mapped and scheduled treatments with an Environmental Protection Agency-approved herbicide began in August 2008. A total of 5 treatments were conducted and the population has since been eradicated. Routine annual monitoring will continue in perpetuity, in order to ensure continued control of French broom at this site.
This species was targeted for removal due to its degree of invasion in the watershed, as well as its predation upon native frogs including the California red-legged frog (Rana draytonii). The South African clawed frog is well-adapted to the local Mediterranean climate, which has enabled it to establish a dense population that is spreading. The mild conditions of southern California enable year-round breeding, which can result in 27,000 eggs per breeding session, per frog, and its tolerance for elevated toxins in water have allowed the population to continue to rise.