Invasive Species

There are several invasive plant and animal species found in the Santa Clara River Watershed, all with varying levels of impact, options for control/management, and project funding. Here is a list of some of the major invasive species:

Tamarisk sp. (Salt Cedar)

The plants are considered to be among the world’s 100 top invaders and one of the most damaging invasive weeds in the western US. The species that are present in the U.S. include Tamarix ramosissima, T. parviflora, T. aphylla, T. chinensis, and T. canariensis, and several hybrid forms between the different species (Gaskin & Schaal 2002). Similar to Arundo donax (Giant Reed), tamarisk invades riparian systems and responds positively to flooding which seems to facilitate establishment. The plants form dense stands, and invaded areas often become completely dominated by tamarisk with few other plant species present.  For more information, visit: http://rivrlab.msi.ucsb.edu/invasive-species/tamarisk

Tamarisk grows in huge, dense stands. (NOAA.gov)

Tamarisk is a fire promoter, even in natural riparian areas. (Tamarisk Coalition)

 Arundo donax (Giant Reed)

Arundo (giant reed) is a perennial, clump-forming grass that has invaded riparian areas in Mediterranean-type, subtropical, and semi-arid climates worldwide. It is the largest of six species in the genus Arundo and is one of the tallest grasses in the world.  Dispersal and reproduction occur primarily through transport of rhizome fragments that break off during seasonal flooding events and are carried to new sites where populations establish.  Arundo has been observed flowering annually between August and October in desert populations, but in coastal habitats of California, flowering occurs irregularly among years and sites (A. Lambert, personal observations).  Its flowers are perfect (Tucker 1990), but neither pollen nor seeds have been documented in North America (Johnson et al. 2006) and no seeds have been found in Europe (Lewandowski et al. 2003).  For more information, visit: http://rivrlab.msi.ucsb.edu/invasive-species/giant-reed

Arundo grows in dense, tall stands.

Often, management requires intensive, mechanical removal.

Delairea odorata (Cape Ivy)

Originating from South Africa, this plant tends to be found in low elevation with preference towards disturbed areas such as stream banks. In California, the vines reproduce only vegetatively, re-sprouting from broken fragments of either rhizomes or stolons.  The vines can climb to heights of up to five meters  and grow up to one foot per month, making this invasive species difficult to control.  Expansion into relatively undisturbed chaparral ecosystems is a disturbing new phenomenon, as these systems have been considerably resistant to non-native species invasions.   For more information, visit: http://rivrlab.msi.ucsb.edu/invasive-species/cape-ivy

Cape Ivy.

Cape Ivy, much like Kudzu, smothers out native species with it’s blanket-like growth.

Potamopyrgus antipodarum (New Zealand Mud Snail)

The New Zealand Mud Snail (NZMS) is found in many water bodies, including estuaries, brackish waters, lakes, large rivers and small streams. This small aquatic gastropod has a history of becoming a pest species in many parts of the world, and its recent introduction into North American waters is cause for concern. NZMS can reproduce relatively rapidly it often reaches densities greater than 100,000/m² in suitable habitat. Ecological effects of the NZMS include out-competition of native sails and a lack of nutritional value for fish. For more information, visit: http://rivrlab.msi.ucsb.edu/invasive-species/new-zealand-mud-snail

A dime is used for size comparison. The New Zealand Mud Snail ranges in size from 4-12 mm. (U.S. Geological Survey)

The New Zealand Mud Snail, a closeup! (U.S. Geological Survey)

For a comprehensive list of invasive flora and fauna found on the river, check out this guide! A useful identification tool for spotting invasive’s along the Santa Clara River.

• Invasive Flora Fauna Guide