The Science of Non-native Species in a Dynamic Delta

Invasion of non-native species is one of the greatest global threats to the integrity of ecosystems and one of the five main drivers of ecosystem change. When a new species becomes part of the ecosystem, it can alter the food web, nutrient and contaminant cycling, abundances of other species, and habitat structure. The resultant changes in ecosystem services (e.g. water quality, water flow, fisheries, endangered species) and even ecosystem stability can impact a broad range of stakeholders and impinge on the responsibilities of many government agencies.

The California San Francisco Bay-Delta ecosystem is one of the world’s most invaded estuaries. Indeed, non-native species comprise much of today’s Delta ecosystem. Non-native species threaten the Delta Plan’s coequal goals of “protecting, restoring, and enhancing the Delta ecosystem,“ and “providing a more reliable water supply for California” as well as state and federal objectives for preserving native species and ecosystems. The Delta Reform Act of 2009 recognized the importance of this issue and stipulated that the Delta Plan should restore a healthy ecosystem by promoting “self-sustaining, diverse populations of native and valued species by reducing the risk of take and harm from invasive species.” Reducing the impact of non-native species is also a core strategy highlighted in the Ecosystem Amendment to California’s Delta Plan.