Do you recruit volunteers from environmental groups and organizations? Perhaps Master Naturalists in your area whose focus is on natural resource issues? When talking to this audience, you’ll want to give extra thought to the most important “whys,” because that will be what motivates time and energy.
Although it’s common to simply say, “Invasives outcompete native plants,” that phrase falls flat for many listeners. Here’s why: the oft-repeated message lacks urgency that prompts action directed at preserving native habitat and wildlife. Without more information, some may assume adding more species, even those not native, improves diversity.
Even though adding species may seem advantageous at first glance, greater in-depth knowledge about how invasive species break down ecosystem interactions can guide all of us to better decisions for a healthy environment and the world of organisms relying on it. Here are a few thoughts to share. Find details in the linked background articles and check out the blogs referenced as examples.
Most plants are toxic to insects.
It takes eons for adaptations to develop and build into symbiotic relationships. Take the monarch butterfly’s ability to use milkweed as food, for example. Milkweed exudes a sticky substance when leaves or stems are broken. It glues the mouthparts of insects closed so they die of starvation. Over time, monarchs grew smarter, learning to first chew through the midvein at the leaf’s attachment to the petiole, preventing the flow of the “glue” into the leaves. Then, developing immunity to the primary toxin in milkweed aided them further. Et viola! The leaves could then be eaten.
This typifies the very definition of adaptation. If invasive plants displace milkweed, though, how long would evolving to use a new food source take? Monarchs are in such decline they aren’t likely to have the time to adapt. Now is the time to remove and control invasives so natives can be restored.
Learn more: “Turf War: the Battle Between Native and Invasive Plants”
Birds depend on plants for food.
Birds eat fruit, seeds, and other plant parts, but they also rely on plants to attract insects used for food. For instance, and their offspring. Without insects as food for the adults to build their own health, and for the larvae they feed the chicks, the risk is great for loss of nestlings. When invasive populations increase, the result is fewer available insects – affecting birds’ diets during the most critical season.
According to Doug Tallamy in his 2016 article in Bird Watcher’s Digest, “Some plants are far better at producing insect bird food than others. For example, oaks support 557 species of caterpillars (bird food) in the mid-Atlantic states alone, whereas non-native Zelkova trees from Asia support no caterpillars at all.
Ninety percent of the insects that eat plants can only eat specific plants; if those plants are absent from our landscapes, so will be the bird food they produce. Unfortunately, this is the case in our yards and managed landscapes when we remove native plant communities that are good at making insect bird food and replace them with vast lawns and ornamental plants from other parts of the world that produce few insects in North America. This oversight must end if we want birds in our future.”
Going a step further, winter birds have chosen the same migration pathways for millennia, expecting the needed high-fat winter fruits and berries to be there as always. When invasives crowd out native plants that provided such vital food, both winter residents and migrants suffer more from cold temperatures, and the water crossings to warmer climates end in tragedy. Birds literally run out of gas, unable to complete the dangerous days-long flight to the south. Only by assuring the right foods remain present year-round is there hope of slowing the decline in bird populations we’ve seen in recent decades. That means controlling the spread of invasives and keeping natives in place.
Read more in this article on how to help migrating birds.
Have you thought about soil?
Invasives affect the soil’s microbial community where eons-old relationships exist. Reducing the soil network’s efficiency as a conduit for nutrients and water to native species is serious, and results when invasives are introduced. The fungi, bacteria and invertebrates can’t always adapt to the damaging changes in root exudates, chemicals in leaves dropped, and a weakened ability to effectively network for nutrient recycling to maintain the natives.
Diversity within the affected ecosystem may increase by species count when invasives move in, but as soil dwelling microbes’ relationships fail, native species start dropping out from the shorter supplies of nutrients and water. It’s a downward spiral stopped only by closely monitoring for invasives and rapidly responding to control them, so natives can thrive.
Learn more about how soil chemistry suffers at the hands of invasives.
In conclusion: Learn more and share what you know!
Complex ecosystem interactions are the functions that result in goods and services we rely on. Invasives interrupt the interactions and degrade the benefits. Share as many “whys” as you can with your volunteers. Help them grasp just how far-reaching impacts from invasives can be. You’ll find an eagerness to act the more they understand. The time investment to train volunteers pays off with growing participation and the commitments you need to stay ahead of invasives.
Teri MacArthur
Teri MacArthur is the Environmental Education Specialist for the Water Conservation Program of The Woodlands Township Environmental Services in Texas. She writes frequent blogs and magazine articles on a variety of natural resource related topics, including invasive species.
