The SuAsCo watershed faces some unique challenges in that the Wild and Scenic rivers flow through both rural and developed land. Invasive species are also an unfortunately common problem across the country, and our watershed is no exception. We are working hard to keep our rivers clean and to control these invasive species with a number of projects. Please read on below to find out more!
Purple Loosestrife Control | Water Chestnut Removal | River Clean-Ups
Purple Loosestrife Control - Galerucella Beetle Rearing
Purple loosestrife is an aggressive invasive plant that grows in wetlands. It is originally from Eurasia, and was introduced for both medicinal and ornamental purposes. Unfortunately, purple loosestrife is still sold in many places because of its bright, purple flowers. Purple loosestrife has little biological benefit where it is not native, aggressively crowding out native species, reducing habitat for waterfowl and altering water flow.
Purple loosestrife if difficult to remove because it grows so quickly, has no native predators, thrives in mildly disturbed soil (a situation we create by trying to remove the plant in the first place), produces many seeds, and has a persistent root stock. In recent years, conservation groups have turned to methods of biological control. Due to the fact that purple loosestrife does not have any native predators, we need to investigate what its predators are where it is native.
Galerucella beetles are also native to Eurasia and feed on purple loosestrife leaves. They will sometimes nibble on other plants here, but need the purple loosestrife to complete their life cycle. This is very important to consider when using a biological control agent, because we do not want to introduce another invasive pest that will take over! Once the purple loosestrife are gone, the beetles will be as well. Realistically, however, we will not be able to completely eradicate purple loosestrife in the United States. So much of it is growing in so many places, our best option to keep it under control with measures like the beetles. Eventually, we hope to establish a large enough beetle population that they will naturally reduce purple loosestrife populations and keep the plant from invading new areas.
Our U.S. Fish and Wildlife Service partners at Great Meadows National Wildlife Refuge and Assabet River National Wildlife Refuge raised Galerucella beetles for several years, and they are making a difference. Early in the spring, refuge staff dig up purple loosestrife to grow as a food source for the beetles they are also raising. When the beetles that are now living in the wild come out from their winter dormancy, staff and volunteers collect the beetles from the wetlands and place them on the cultivated loosestrife plants. The beetles and plants are protected from predators so the beetles can mate and lay eggs. Once the eggs have hatched and the larvae have grown into adult beetles, they are released back into the wild so they can continue to feed on purple loosestrife and overwinter to breed the following year.
Water Chestnut Removal
Water chestnut is an invasive aquatic plant that grows in shallow waters in freshwater ponds and slow-moving rivers. Like purple loosestrife, it is originally from Eurasia and was introduced as an ornamental plant. Water chestnut is a problem because it is also an aggressive invasive plant, and will form dense mats across the water's surface. The mats block out sunlight so other, native aquatic plants cannot grow, alters and reduces habitat for native animals, and are almost impossible to navigate boats through. Its seed is a hard, spikey nutlet, painful to step on, that roots in the sediment, but can remain viable as a seed for up to 12 years. This means that management and eradication plans must be long-term and span many years to truly be effective.
Our U.S. Fish and Wildlife Service partners at Great Meadows National Wildlife Refuge own a large, mechanical aquatic harvester that they loan to a number of other partners in the watershed to use throughout early and mid summer to harvest water chestnut. The harvester can operate in water that is several feet deep and has cutting blades that slice through the water chestnut stems. A large conveyor belt brings the cut plants up and onto the barge portion of the harvester, and the plants are later transferred to a dump truck on shore. The harvester can only go where the water is deep enough, so we rely on volunteers in canoes and kayaks to pull water chestnut by hand where the water is too shallow for the harvester.
Controlling water chestnut is a time- and labor-intensive process that takes many years, but we are seeing progress. Some ponds in the watershed have nearly successfully eradicated water chestnut and are now just conducting continued monitoring and occasional hand-pulling.
River Clean-Ups
Our rivers flow through a relatively densely populated and developed area, and they unfortunately have had a lot of time to collect debris and pollutants. The Organization for the Assabet, Sudbury, and Concord Rivers (OARS) hosts an annual river clean-up in the fall, and has been doing so since 1986! They began work focusing solely on the Assabet River, as they used to be The Organization for the Assabet River. Since their inception, they have expanded to include all of the rivers in our watershed and are an extremely valuable partner in our Wild and Scenic River conservation efforts.
Even though we have been cleaning up our rivers for over 25 years, there is still much more to remove. Less trash and debris are thrown into the rivers now, but so much remains burried in the sediment from years gone by that cleaning the rivers is a long-term project.
In mid September, 2012, OARS hosted their 26th annual river clean-up. In an effort to reach even more of the watershed, they expanded to include six different clean-up locations. Over 200 people came out and volunteered to haul trash out of the rivers. Check out the OARS event page for tons of great photos of the hugely successful event.
