Nonnative Species Blog

Keeping invasive plants at bay is a powerful way to help native plants and wildlife flourish. But that’s no easy task when you aren’t quite sure where they are; first, you have to find them. The One Tam Conservation Management Team recently set out to do just that to help land managers keep one particular species of concern off of upper Mount Tamalpais: thoroughwort (Ageratina adenophora).

Invasive plants don’t see our property lines. The five partners that make up Marin County’s One Tam partnership know this, and they teamed up to create an Early Detection and Rapid Response program tasked with identifying and managing invasives across jurisdictions on Mt. Tamalpais. With early leadership from the Inventorying & Monitoring Network’s Invasive Species Early Detection Program, crews from One Tam surveyed over 400 miles of roads, trails, and stream corridors.

As part of a collaborative effort to manage Japanese knotweed within the Lagunitas Creek watershed, a team of ecologists from One Tam’s Conservation Management Program conducted a four-week survey to map all Japanese knotweed patches in the riparian corridor on public lands. Visit their Story Map to learn more about the creek, the plant, the surveys, and why it all matters.

This month, Golden Gate National Recreation Area and San Francisco Bay Area Network biologists discovered a large population of invasive New Zealand mudsnails in Redwood Creek at Muir Beach. A taxonomist at California State University, Chico helped confirm the snails’ identity.

Homeowners, land managers, and coho salmon and all share a common concern along Lagunitas Creek in Marin County: Japanese knotweed. The plant is one of the world’s most invasive species, and was first reported in the area in 2011. This year, an early round of Japanese knotweed treatments is focusing on an area along Lagunitas Creek where a coho salmon habitat enhancement project will be taking place later in the summer.

Native to Japan, China, and Korea, Japanese knotweed is considered the 10th most invasive plant in the world. It is hardy enough to survive on the slopes of active volcanoes and strong enough to penetrate concrete, making it a threat to both natural and developed areas. Although it is not widespread in California, it is found at a number of sites in Marin County. Roughly a third of the known populations are on National Park Service land in Lagunitas Creek.

National Park Service and Golden Gate National Parks Conservancy staff are working on cotoneaster removal at several project sites in the Golden Gate National Recreation Area including Oakwood Valley and Tennessee Valley. Cotoneaster—an invasive woody shrub with red berries that are readily dispersed by birds—forms dense stands that block all light to the understory.

A new edition of Early Detection News for July 2017 is now available. Brought to you by the Invasive Species Early Detection Program and Weed Watchers, this newsletter has the latest on invasive plants in the Bay Area.

A new edition of Early Detection News for June 2017 is now available. Brought to you by the Invasive Species Early Detection Program and Weed Watchers, this newsletter has the latest on invasive plants in the Bay Area.