Invasive species, also known as exotics, are plants, animals, insects, and aquatic species introduced into non-native habitats.
Often, invasive species travel to non-native areas by ship, either in ballast water released into harbors or attached to the sides of boats. From there, introduced species can then spread and significantly alter ecosystems and the natural food chain as they go. Another example of non-native species introduction is the dumping of aquarium fish into waterways.
Without natural predators or threats, these introduced species then multiply.
Invasive species also put water conveyance systems at risk. Water pumps and other infrastructure can potentially shut down due to large numbers of invasive species.
Invasive Species in California
Since the arrival of Western settlers, California has been troubled by invasive species. In one prominent example, eucalyptus from Australia has thrived across the state.
The state’s waterways are also home to some of the densest concentrations of invasive species in the world. This is the case in San Francisco Bay, with its busy ship traffic from around the globe, and the Sacramento-San Joaquin Delta.
In the past decade, invasive species threats have included trout and bass in Lake Tahoe, water hyacinth in the Delta, and zebra and quagga mussels in Southern California.
In addition to water hyacinth clogging infrastructure, invasive fish such as carp and bass have dramatically altered the Sacramento-San Joaquin Delta. Some of these species eat the same food smelt depend upon. Others alter the environment by decreasing turbidity, making young smelt more vulnerable to predators.
Along the Colorado River, once vibrant species such as the razorback sucker and the bonytail have become endangered. And on the shore, once thriving cottonwoods have been crowded out by tamarisk, salt cedar and other exotic plants that erode beaches and degrade wildlife habitat.
In response, California passed Assembly Bill 984, directing the state to develop a comprehensive plan for removing tamarisk the entire length of the Colorado River system.
The Lower Colorado River Multi-Species Conservation Program, launched in 2005, aims to balance use of Colorado River water resources with the conservation of native species and their habitat. The MSCP works toward the recovery of species currently listed under the Endangered Species Act.
California also passed strict regulations on ballast water release in 1999. Further treatment and compliance standard deadlines were announced in 2006.
Under the plan, ships with 5000 metric tons of ballast capacity must meet the 2006 ballast standards by 2014. Ships with more than 5000 metric tons have until 2016.
However, these deadlines are being challenged and may be pushed back.