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 adopted legislation in 1999 requiring ballast water management. In 2006, the State Lands Commission issued regulations setting ballast discharge standards and deadlines. Under the current plan, ships must meet the 2006 ballast standards by 2020.
In 2017, the State Lands Commission adopted regulations for ballast water management. Among other things, they required arriving vessels of a certain tonnage to discharge only the minimal amount of ballast water essential for operations and to minimize or avoid uptake of ballast water in areas with known infestations of invasive species.