Invasive Plant Mapping and Management

OARS is mapping invasive aquatic plants - focusing mainly on water chestnut - on the Sudbury, Assabet, and Concord Rivers to map known populations, find new infestations, and prioritize and track the progress of water chestnut pulling. Mapping started in 2012 on the Assabet River, and was extended to the Sudbury and Concord Rivers in 2013, 2014 and 2016.

Invasive non-native species
Read more about invasive species on the Assabet, Sudbury, and Concord. Part of an effective invasives management program is knowing what and where: early identification, prioritizing efforts, and tracking progress. OARS’ mapping includes a number of invasive aquatic plants in the rivers: water chestnut (know infestations on all three rivers), water hyacinth ( found once on the Assabet), water lettuce (found once on the Assabet), Eurasian and variable milfoil (infestations on the rivers and many ponds), European water clover (found in the Sudbury River), curly pondweed, and fanwort.

Mapping Methods
July 2012, trained OARS’ volunteers took to the river in canoes and kayaks to map invasives. Handheld GPS units let volunteers easily find their location, estimate the size of the assessment grid squares, and enter the data on the spot.
In 2013, 2014 and 2016, as part of the SuAsCo CISMA water chestnut control effort, OARS' summer interns surveyed all of the Sudbury, Assabet, and Concord Rivers for water chestnut.
View the maps showing the density of water chestnuts on the rivers' main stems from the survey. In 2018, OARS did a pilot study to test whether a drone could be used to do aerial mapping of water chestnut.

Water chestnut mapping of the Crow Island area of the Assabet River, 2012

More about OARS’ mapping
2012 Presentation on Invasives Mapping (made to SuAsCo CISMA)

Managing invasive plants
Management options for invasives depends on the biology of the particular species. See OARS' "Water Chestnut Management Guidance & Five-Year Management Plan for the Sudbury, Assabet, and Concord River Watershed." The Guidance compiles the most recent research on the lifecycle and control of water chestnut, provides guidance on permitting of control efforts (for both permittees and Conservation Commissions), and lays out a management plan for the Sudbury, Assabet and Concord Rivers. For example: water chestnut can be managed by physical removal (with a mechanical harvester or hand-pulled) because the plant regenerates from seed; milfoil, however, can regenerate from plant fragments and from seed and so must be managed by more careful removal of the whole plant, chemical treatment, and/or bottom barriers.

Since 2008, OARS volunteers have been hand-pulling water chestnut on the Assabet River, starting with patches in the Stow section of the river. Sections that have been pulled multiple years show significantly fewer plants. In 2013, our handing-pulling efforts expanded to included the Sudbury River in Saxonville. Read more and see the pictures!

In 2015 and 2016 OARS' Rapid Response Team spent the summer removing all water chestnut plants from the Assabet River by hand, in addition to the volunteer pulling efforts. This work was supported by funds from two environmental penalty payments for stormwater violations in the watershed. Starting in 2017 the Rapid Response Team has hand-pulled water chestnut from all three rivers. This work was supported by the Greater Lowell Community Foundation in 2017. This thorough and consistent effort has yielded significant improvements, but securing funding to maintain it is a challenge.

OARS' Water Chestnut Management Guidance & Five-Year Management Plan, released in 2017, will help water chestnut management state-wide. We compiled current research and experience from the field, and contacted municipalities and organizations throughout the region. A survey was sent to conservation commissions statewide with the help of MACC. Permitting guidelines were developed in collaboration with MassDEP to help groups comply with wetlands regulations and bylaws. The Management Plan is implemented through the "Water Chestnut Subcommittee of the SuAsCo Cooperative Invasive Species Management Area (CISMA)", chaired by OARS. This work was supported by the Nyanza Natural Resource Damages Trustee Council, comprising U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, and MassDEP.

Thanks to Mass Audubon for their technical assistance and to SuAsCo CISMA for the use of their MobileMappers and their support of our work with funding from the Nyanza Restoration Fund.

Continued thanks to the the ESRI Conservation Program for ArcGIS software.

Thanks to the ERM Foundation for their support.

Other References
Milfoil treatment WA Department of Ecology
Massachusetts Practical Guide to Lake Management (aquatic plant management methods starting on page 102)