Invasive plants come from all over the globe, accidently or purposefully spread for various reasons. Some of these plants were brought as part of erosion control or wildlife enhancement programs, established along roads and throughout the landscape before their negative effects were understood. Others were widely used for ornamental purposes and intentionally introduced to US soils for their aesthetic qualities. Whatever the reason for their arrival, one thing is clear: these plants, and all of the harmful environmental and economic impacts they bring, are here to stay unless we take action.
The classification of a plant as an invasive species can be confusing. Some non-native plants establish themselves in a community, without displaying invasive tendencies and causing much damage to the native populations. On the other hand, native species, such as poison ivy, can end up overwhelming and outcompeting other plants such that they cause some of the same impacts as exotic invasive species. Exotic invasive plants are generally species that have been introduced into our local landscapes, usually from outside of the US, and exhibit traits that allow them to grow and spread more aggressively than our native plants. These characteristics that give them a competitive advantage include producing many seeds with high rates of germination, resprouting or vegetative reproduction, deterring native herbivores, and tolerating harsh environmental conditions.
The impacts of these plant invasions are present throughout the New Hampshire. Along the side of the road, oriental bittersweet climbs and completely smothers native trees. Japanese barberry and multiflora rose form thickets of thorns that are inhospitable for other plants or animals. However, not all of these invasive plants have such direct or obvious impacts. For example, the fruits of invasive honeysuckles tend to be more numerous but less nutritious than those of their native counterparts. If migratory birds choose the invasive berries that are an inadequate food source because they are more readily available, it could be harmful to bird populations. At a broader level, the characteristics that make invasive species so successful in new environments allow these plants outcompete and displace native species. The resulting reduction in biodiversity has widespread impacts which ultimately diminish the ecosystems and natural communities that make this region beautiful.
It takes careful coordinated action from both individuals and organizations across the region to make a difference. You can start by learning to properly identify invasive plants in your backyard or other areas you visit. It’s also important to learn the proper removal techniques. Not only do you want to be sure you are removing the correct plant, but you need to consider different removal or disposal methods depending on the species. Japanese knotweed, which is prevalent along roadsides or disturbed areas, can be particularly difficult to manage as even small root fragments can lead to re-establishment of the population. For other species that reproduce by seeds, such as autumn olive or burning bush, mechanical removal in the spring before the plant produces fruits can be effective. The NH Department of Agriculture, UNH Cooperative Extension, local conservation organizations, and town conservation commissions can provide simple identification guides and other resources to help you take action around your home.
Removing terrestrial invasive species takes focused, collaborative, and long-term effort, which is now underway in the Squam Watershed. Conservation organizations including the Squam Lakes Association, Lakes Region Conservation Trust, the Squam Lakes Conservation Society, the Squam Lakes Natural Science Center, and conservation commissions from the five watershed towns (Ashland, Center Harbor, Holderness, Moultonborough, and Sandwich, are all part of this concerted fight against exotic invasive plants. The Squam Lakes Association is kicking off the 2108 invasive removal effort on May 19th with a Squam Watershed-wide weed pull, with locations all around the lake so volunteers can help remove invasive plants within their communities. It takes a coordinated effort over years to successfully control established invasions. Learn more about the SLA’s May 19th effort on their website: squamlakes.org.
Individuals can get involved through their town conservation commissions, local conservation groups, and on their own property to reduce the spread and impact of invasive species. The presence of invasive plants is a serious threat to the environmental health of the region, but with coordinated, long-term effort we can protect our forests, fields, wetlands, and trails.