By Zachary Byers, Forestry Major, Penn State University
Our nation’s lands hold a wealth of diversity. Our lifestyles and culture have affected this diversity. Among the more negative impacts on this diversity has been our introduction of exotic plant species that become aggressively invasive and threaten our native plant species. Most of these plants, including the garlic mustard and Japanese barberry, were deliberately introduced. The reasons for introducing these plants vary greatly—for example, the plants may have been considered ornamentals, or perhaps they were a quick source of nutrition or even offered the hope of preserving soil or water quality.
It’s not that these invasives are inherently bad; they simply cause too much stress in an environment where they can affect other species. This idea is very straightforward and can be explained in no more than a couple minutes, such as in this video: https://www.youtube.com/watch?v=HAY_UsGjyZk.
Among the greatest misconceptions of invasive plants is that many people still confuse them with exotic plants. An exotic plant is any plant that does not natively originate from a specific area, and not all exotic plants become invasive. An invasive plant goes a step beyond: it’s a plant that was not only brought to our land from elsewhere but also poses a threat to our native plant species. For most agencies and legislative entities dealing with invasive plants, their management practices are typically similar: removing or controlling the plants depending on how much the plants threaten the native plants of the area. Total systematic removal of invasive plants on most federal and state lands is rather uncommon; however, because the plants are regarded as potential threats, various land management techniques are deployed to suppress them.
To help others better understand invasive plants, it’s important to explain why they’re considered invasive in the first place. At first glance, many invasive plants may seem completely harmless. In fact, they may even have some degree of value; they may be aesthetically pleasing, for instance, or maybe provide an ecological benefit for their immediate environment (such as enriching the soil with nutrients). If we look at the bigger picture, though, we see that these plants can cause tremendous stress to native plant and animal species. They occupy living space, use resources other plants need for growth (and, in doing so, affect the animals that feed on those plants), and compete for natural roles within an ecosystem. Some even create secondary, toxic compounds that displace other species within reach.
In areas affected by invasive plants, the issue is not so much whether the plants should be controlled or even eradicated in a general sense, but whether the plants are truly invasive. This means that invasive plants have to be handled on a species-by-species basis, not by taking the same action for all invasive plant species. Multiflora rose, for example, is a species that has become well established in Pennsylvania but is originally from Asia and was introduced for soil conservation and to provide “living barriers.” Since its establishment, it’s been valued further as cover for small game, for its aesthetic beauty, and as a source of forage. The issue lies in the plant’s hardiness (far exceeding native rose species) that allows it to form large, shrubby masses that can become intrusive and very difficult to remove.
Opinions can differ greatly on the value of an invasive plant in their ecosystem, making it difficult to agree on how to best manage the plant beyond continual suppression and also making the possibility of large-scale eradication highly unlikely.
Of course, it’s also important to ask whether large-scale eradication is even possible. Most invasive plants still exist within our lands because they’re so resilient against both man and nature’s attempts to remove them. In fact, you could go on just about any piece of state or federal land with a checklist of invasive species and spend hours ticking off examples dotted here and there. In a perfect world, it would be great to simply pluck out every threatening bush, stump, or blade of grass from an area, but of course that isn’t possible.
But one promising method of controlling invasive plants is becoming increasingly popular: the use of prescribed (controlled) burns. Suppressing fire was the norm for many decades; in recent years, though, the value of prescribed burns has been gaining recognition. Our native plant species have not yet lost their ability to recover from low-intensity burns; however, many invasive plants have little to no ability to recover from fire even in their native habitats. It’s true that running a cleansing blaze of fire throughout the state wouldn’t be a total be-all, end-all solution to our invasive plant problems. It would, however, provide us with an extremely valuable tool for regaining control of areas that invasive plants have damaged.
In a way, invasive plant species are likely to be our environment’s “criminals” forever, murdering native species and stealing valuable resources. If we were to let the lands follow nature’s course, then over time, evolution would probably strike an ecological balance by integrating these plants into their environment. But letting nature follow its course would cost us a great deal of the species that we cherish so deeply. In my opinion, policing invasive plant species, as we have for years, is truly our only option. Today we are more conscious about the effects of invasive plants than we were in the past. These invasive species are no longer strangers to us.; we know what they are and have the tools to keep them in line. All that’s left for us is to stay mindful and do whatever we can to keep that long list of invasive plants from getting any longer.