That little yellow flower that blankets our trails every spring may seem like a cheerful welcome to the season, but in all reality, their presence is concerning. This flower, called Lesser Celandine, literally blankets the trails, preventing other native plants from growing. This is just one example of an invasive plant species.
An invasive plant species is defined as one that is not native (not here before European settlement. In Bucks County, this dates back to the early 1600’s) to an area and can cause harm to the environment, economy, and human health. These plants were often introduced by European settlers to be used as land cover, natural fences, or simply as “pretty” plants. While they had good intentions, knowing that the plants were kept in check by environmental conditions, pests and diseases, and wildlife back where they came from, they did not realize that without those same conditions, the plants would become aggressive and adapt very well to their new environment.
These invasive species have now spread wildly and they have a significant negative impact on the ecosystem. Due to their tendency to rapidly reproduce, biodiversity is severely reduced as the invasive species grow much more quickly than the native plants. Invasive species threaten over ½ of the endangered native species. In Riparian zones (bits of land that run along water bodies), invasive species degrade the soil quality, removing valuable nutrients that other native species require, therefore causing them to die out. When these native species die out erosion quickly takes place, causing soil and sediment to fall into streams, creeks and rivers.
Fortunately, plants and animals depend on each other and must evolve and adapt in order to survive. Native plants may develop new traits via “survival of the fittest” that help them to compete with the invasive species. For example, Garlic Mustard produces a chemical that kills off fungi that help native plants use the nutrients in the soil efficiently. The more native plants are present, the more chemicals the Garlic Mustard produces so that it can take over. It is now discovered that Clearweed, a plant native to Georgia, was able to evolve to battle off the nasty chemicals. Now the problem comes when it was noticed that the Clearweed that was resistant to the chemical was less able to thrive on its own without Garlic Mustard present since it had adapted to having the invasive plant around. (Click here to view the details about this experiment and discovery)
Wildlife such as insect-eating bird populations have decreased since many invasive plant species are toxic to insects, another trait that helps them grow prolifically. However, some birds have adapted to the plants by using them as nesting sites. Many of these invasive plants protect the birds from predation, allowing the populations to balance out a little bit. Unfortunately, this process of co-evolution takes time and native plants and animals may need more time to adapt than the invasives will allow.
Plants and animals don’t have to take the time to evolve and adapt if we ensure the survival of native plant species. Aside from being accustomed to the wildlife, pests, diseases, and weather here and therefore being able to grow at a steady pace, native plants have an obvious importance to the ecosystem.
Native plants that grow in Riparian zones increase soil stability and reduce the impact that erosion has on the body of water. They also add biodiversity that causes the soil to be more nutrient rich. This allows for the rest of the plants in the area to thrive as well. There are many native plants that are also wonderful pollinator attractors. The more pollinators that are flying and buzzing around, the better the plants chances are of spreading its genes. In the garden, natives are great because they are used to the weather conditions here and therefore don’t need as much fertilizer as non-native plants would. This can save the gardener money and can reduce the effect of nasty runoff from chemical fertilizers!
The next question is – how can you help reduce the amount of invasive species? It may seem like a big task, but it’s very feasible. Since invasive species will take over an area, minimize the amount of native plant disturbance. If the native community is displaced, an invasive species will be more than happy to move in! If you have invasive species in your yard (common ones include Garlic Mustard, Spotted Knapweed, Crown Vetch, Dames Rocket, Lesser Celandine, English Ivy, Kudzu, Autumn Olive, Multiflora Rose, Wineberry, and Japanese Stiltgrass) get rid of them before they become a problem and go to seed. Once you have removed them, plant natives! The environment will thank you.
Check out these links for some comprehensive lists and guides to identifying invasive species.