Invasive Plant Mapping

OARS is surveying invasive aquatic plants on the Sudbury, Assabet, and Concord Rivers to map known invasives, find new infestations, and prioritize and track the progress of water chestnut pulling. Work started in 2012 on the Assabet River, and extended to the Sudbury and Concord Rivers in 2013.

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 focuses on a number of invasive aquatic plants in the rivers: water chestnut (know infestations on all three rivers), water hyacinth ( found on the Assabet), water lettuce (found on the Assabet), Eurasian and variable milfoil (infestations on the Sudbury and many ponds), European water clover (reported in MA), curly pondweed, and fanwort. Future mappings may include some wetland species including purple loosestrife and common reed.

Mapping Methods
July 2012, trained OARS’ volunteers took to the river in canoes and kayaks to map invasives. MobileMapper GPS units, configured to take data input in the field, let volunteers easily find their location and estimate the size of the assessment grid squares.
In 2013, 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 maps showing the density of water chestnuts on the rivers' main stems, developed from the GPS/GIS data collected.

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. 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!

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.

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