Erosion is a natural process than rivers undergo as they meander, or move back and forth across their floodplain. However, clearing of land, building structures that permanently alter the river’s course, and removing trees and shrubs whose roots help stabilize the banks of the river all increase the rate at which the slopes deteriorate. Sediment is then released into the water, which decreases water quality, and the removal of the tree canopy results in warmer water. There are many ways to reduce erosion, but a common natural method is to re-introduce native species.
In 2015, a management plan was developed by a member of our board for a tree nursery, in place since 2011 and located on land donated by Sandra Estey in the McLean’s Flats area. The tree nursery was developed to support active reforestation and riverbank stabilization projects along the Nashwaak River and, in particular, to provide healthy trees for the Nashwaak Greenway project. Starting in 2016, NWAI increased its production of Silver Maple (Acer saccarinum) so that by 2018 at least 1,000 three-year old trees will be ready annually for planting along disturbed sections of floodplains and eroded river banks of the Nashwaak in order to re-establish this critical habitat that these forests provide to sensitive and species at risk.
Floodplain forests are critically important ecosystems. One of the main benefits they offer to the river is their ability to mitigate flood damage by absorbing large amounts of water and slowing the speed and reducing the height of a flood. Planting Silver Maples can significantly reduce soil runoff and erosion along a riverbank. A mature Silver Maple can draw up and release into the atmosphere 200 L of water every hour (Kozlowski and Davies, 1975). In addition, their canopy shades the river and helps to moderate its temperature. Riparian forests (those along the banks of a river) provide habitat for many different species of animals and plants. For these reasons, NWAI is committed to restoring the Silver Maple floodplain forest communities along the banks of the Nashwaak River.
At the end of August 2016, four staff members of NWAI headed out the McLean’s flats to plant one-year old Silver Maples. These seedlings had been collected by volunteers and planted in plugs of soil. Over the course of two days, the beds were marked at intervals and 1,250 Silver Maple seedlings were planted in the nursery. In the spring of 2018, these trees will be large enough to plant along the Nashwaak River, particularly in retired hay fields. These areas are difficult to restore because the tall grasses will outcompete small trees. The bigger, three-year old trees will be large enough to withstand this competition and thrive. As they grow, they will help stabilize the banks, reducing erosion and improving water quality and habitat for all kinds of fish, aquatic organism, and for the human residents of the Nashwaak as well.