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Towards a Deeper Understanding of Native and Introduced Species Photos: Merry Lea Environmental Learning Center of Goshen College Introducing ecological complexity to your lesson plan helps dispel harmful myths about the impact of invasive species By Lisa Zinn, Jonathon Schramm and Laura S. Meitzner Yoder T HE ISSUE OF INVASIVE SPECIES has arisen as an important theme in environmental conservation and environmental education. When teaching youth about native, introduced, and invasive species, it is tempting for educators to convey this simple message: Native = good; non-native = invasive and bad. Although simplifications are often important for educators to convey complex messages to students, this particular message poses special risks for environmental educators. Learners may inadvertently demonize individual species, without any awareness of the underlying ecological principles—disturbance, niche, and competition—that contribute to species dominance in an ecosystem. After a day of removing invasive plants, students may take home a view that methods of control are relatively straightforward, and that control is urgently needed, while lacking understanding of the possibility for prevention. Further, a focus on invasive plants in natural ecosystems may not help students to link this phenomenon to our food system, which relies heavily on introduced species. This deepens the mental divide that many people have in their thinking about natural and managed ecosystems. In other words, valuable opportunities for deeper ecological understanding among students are being lost in favor of a specific focus on removal of only a few key invasive species in our ecosystems. Is there a problem? After experiences we had teaching about invasive species at an informal environmental education center, we began to rethink the language we used to teach about invasive species. It became clear to us that terms such as alien, invasive, and non-native had different connotations for the recent immigrants to our region than they have for long-term residents. This prompted us to revisit our approach, with the intent of developing more ecologically meaningful ways of talking about issues related to species invasion. We hope to encourage teachers to examine the ways they are teaching invasive species to include more of the ecological complexity that is often lost as we try to motivate students TEACHING ABOUT INVASIVE SPECIES – PERSPECTIVES PAGE 7 to action. By grappling more fully with ecological realities, we believe students will be better positioned to transfer their understanding to new situations and species they will encounter later. Invasive species education should be more aligned with the broader goals of education for sustainability, interpreting ecological complexity in ways that people can understand and use. The challenge with invasive species is to “illustrate such complexity, without overwhelming or confusing the learner” 1. In our field-based teaching, one of our goals is to introduce students to ecological principles that affect changing populations of native and introduced species. We will focus on three of the most common misrepresentations of introduced—and particularly of invasive—species that we have heard educators use (and used ourselves). This particular example concerns an invasive plant called garlic mustard (Alliaria petiolata), which was introduced to North America in the mid-1800s and is now considered invasive over much of the continent2. As environmental educators many of us have found ourselves explaining this plant to students in something like the following manner: “Not only does garlic mustard produce a huge number of seeds each year but it also emits chemicals into the soil around it that kills other plants or keeps them from growing. This allows the garlic mustard to completely dominate the area so none of our native plants and flowers can grow there. This creates a monoculture on the forest floor, which means only one species can grow here, where originally there was a huge diversity of native herbs and flowers. This is a problem!” This explanation provides a quick way to introduce a group of students to the invasive species they are encountering on the trail. However, explaining invasive species in this manner can easily lead students to believe several myths about invasive species: “The Myth of the Villainous Invasive,” “The Myth of Black and White Distinctions” and “The Myth of Static Ecosystems.” These myths are easy to convey when we are teaching on the trail, but can be damaging to students’ perceptions of non-native species. The Myth of the Villainous Invasive When we teach this myth, we teach the false idea that invasive species somehow intend to dominate ecosystems and exclude others more than other species do. After hearing the explanation above about garlic mustard, students might come away with the idea that garlic mustard is a dastardly plant that does not play fair. It is a bully that comes in and takes over by using sneaky tactics against our well-behaved native species. Its intention is to come in and dominate the landscape, leaving no room for pretty wildflowers. In addition to anthropomorphizing the garlic mustard, this myth also gives students the impression that the solution to this lack of biodiversity on our forest floor is as simple as getting rid of the garlic mustard. While this is part of the solution, we also want to help students understand that it will take more thinking. We have to consider soil nutrients, canopy disturbance, excessive herbivore pressure, and other factors that are influencing the “evil” garlic mustard’s rapid growth, the relative scarcity of many native herbs, and also our solutions to the problem. PAGE 8 A better approach may be to talk about specific mechanisms the garlic mustard has that have allowed it to thrive so well in both its original and new environments. You could begin by asking students to brainstorm about challenges that plants have to their survival (access to sunlight, competition for water and nutrients, getting seeds to a location where they can grow, predators, diseases, etc.) and then explain that all plants have adaptations or survival strategies to deal with these challenges: “All plants have adaptations to help them survive within their niche, or specific habitat. One of these adaptations is that garlic mustard produces lots of seeds at a time. Why do you think this might make it good at surviving in this forest? Garlic mustard also produces chemicals that are released into the soil to keep other plants from growing. There are native plants that use this chemical strategy also, like the black walnut tree. Why would this help the garlic mustard survive in a place where it is competing with other plants for sun, nutrients, and water? These adaptations helped it survive in its native landscape, and these same features help garlic mustard spread rapidly when humans move it to a new location. In the new location, there are fewer predators and diseases to attack it, and plenty of areas of disturbed land for it to grow. Not all plants and animals that are moved around the world to new locations take over like garlic mustard. This usually happens when a species gets to a new place, where it happens to grow really well: places where farming, grazing and logging have opened up many niches for growth are especially easy places for an invasive to thrive. In a habitat like this, it will be able to spread rapidly and out-compete the native species growing there for years before it came. Why do you think this could be a problem for the health of an ecosystem? It can decrease the ecosystem’s diversity and threaten some native species populations. Can you think of any ways we could work toward stopping the spread of invasive species? What would we have to consider?” We suggest that if we focus on these characteristics of introduced plants as things that are common to species around the world, rather than their exotic origin and aggressive growth, we can help students to gain an appreciation of ecological constraints that affect all species’ abundance and distribution3,4. This in turn can help them to develop a stronger understanding of how our management efforts can effect underlying mechanisms, rather than only removing the offending species. The Myth of Black and White Distinctions When we teach this myth, we imply that all plants from outside our region are “invasive,” and all native plants from inside our region are “not invasive.” This is problematic for a few reasons. For one, students may not realize that only a minority of species introduced to a habitat will spread on their own (naturalize), and only a minority of those will TEACHING ABOUT INVASIVE SPECIES – PERSPECTIVES spread enough to be called invasive. Those introduced plants that do not become invasive are what we call “non-native” or “introduced,” but are not necessarily “invasive.” Also, this myth doesn’t work for a species that may be harmless and native to one region but can wreak ecological havoc when they become invasive in another part of the globe. This means the native plants from our backyard might become invasive when taken to another continent. Most importantly, this simplified distinction neglects the role of human activity in spreading species around the globe. This is especially true of our agricultural species, or others that we have an economic interest in promoting. We rarely think of wheat or tomatoes or cassava as invasive, but all do reach unnaturally high abundances, at least where we cultivate them. Likewise, seeds that often accompany our crop plants, e.g. weedy species from fields, often are accidentally introduced in high densities. Although it is very easy for educators to slip into this shorthand way of discussing invasive species, it is crucial that we help students understand the ecological realities. Species—invasive or otherwise—rely on certain conditions for survival that they can find in different places if they are moved around by people or other natural forces. This can reinforce that it is not simply the origin of a species that determines whether it is invasive or non-invasive, but instead the interaction between species’ traits and the community of which it is a part5. Continuing with the garlic mustard example: “Have you ever wondered why garlic mustard got to North America from Europe in the first place? It didn’t get here on its own; instead it was intentionally planted by settlers from Europe who liked to use this plant both for food and also for medicine. Naturally, they thought it was a great idea to bring this important plant with them, so they planted it very widely across the eastern United States. It slowly began to spread into natural parts of the landscape, such as our forests. They had no idea it would become invasive at that time, but now we are having to deal with the consequences. Can you think of any North American species that might have been introduced to other parts of the globe? In fact, many species of plants and animals have been moved around the world, both accidentally and intentionally by people, everything from tomatoes to Canada goldenrod to beavers and mink.” Emphasizing the unique histories of each species can help students to remember to think ecologically about them, to consider their survival needs and interactions with habitats old and new. The Myth of Static Ecosystems When we teach this myth, our students learn that ecosystems have one set way they should be and that any changes that happen due to “evil” invasive species are harming the system. In the example above, students could also take away TEACHING ABOUT INVASIVE SPECIES – PERSPECTIVES PAGE 9 we will share our ideas and I want you to explain why you think any of these changes will occur.” A rich follow-up discussion in the classroom could involve having the students investigate other invasive species in their area with a range of population trajectories: some that have fallen from initially high numbers into lower but stable sizes (like the multiflora rose), some that have been successfully (or unsuccessfully) managed or controlled by humans (like purple loosestrife), and some that have populations that are still increasing with an unknown ecosystem response in the long-term (like garlic mustard). Teaching about invasive species can be a difficult task: the high level of ecological complexity can be difficult to communicate to students. As environmental educators, it is easy to fall back on catchy phrases and sound bites that help us communicate the main ideas simply but often inaccurately. We hope the ideas presented above will help us as educators capture a broader range of ecological principles in their complexity. We encourage both formal and informal educators to consider how teaching invasive species might be strengthened so that important ecological concepts are conveyed, but also so that students find these issues interesting and accessible. Informal educators can help by trying to avoid these myths when taking students on the trail at nature centers. Formal educators can help by following up on field trips with discussions about the complex issues of native species. Instead of teaching the oversimplified message that “invasive species are bad!” how about: “Invasive species can teach us important lessons about how we use the earth.” the idea that the forest has always been rich in diversity and that only changed since the garlic mustard invaded. Ecologists and environmental educators can fall prey to this myth too, as human lifetimes are so short that we forget how dynamic ecosystems are and that many of the landscapes where we study and teach have a history of dramatic human and natural disturbances e.g. fires, glaciation, flooding, etc. Explaining the complex dynamics and changes that ecosystems go through over time can be a difficult concept to communicate, especially to young students who don’t have a lot of personal experience with changing landscapes. One potential activity is to have students spend some time thinking about how a landscape might have looked in the past. Using our garlic mustard example you could do a simple trail activity using writing or drawing: “As you look at this area do you see any clues to what this landscape might have looked like 50 years ago? What about 100 years ago? How big are the trees? Does it look like they would have been here? This landscape has changed a lot over time. Do you think some plants are new here? Do you think some plants are gone? Yes, ecosystems are changing. Scientists often use the word dynamic to mean that they are always shifting and changing. Take a minute and write (or draw) a description of what you think this area will look like 100 years from now. Will these trees still be here? Will garlic mustard still be the dominant plant on the forest floor? When we are done PAGE 10 Lisa Zinn teaches in the Sustainability and Environmental Education Department (SEED) at the Merry Lea Environmental Learning Center of Goshen College in Goshen, Indiana. Jonathon Schramm also teaches in SEED at Merry Lea, working with graduate students on environmental education curriculum design. Laura S. Meitzner Yoder directs the Human Needs and Global Resources program at Wheaton College, in Wheaton, Illinois. She works with undergraduates who undertake cross-cultural experiential learning on justice, poverty, and transformation. Notes 1. McKeown, Rosalyn. Education for Sustainable Development Toolkit. Knoxville, TN: University of Tennessee, Energy, Environment and Resource Center. 2002. 2. Meekins, J.Forrest and Brian C. McCarthy. “Competitive ability of Alliaria petiolata (Garlic Mustard, Brassicaceae), an invasive, nonindigenous forest herb.” International Journal of Plant Sciences 160.4 (1999): 743-752. 3. MacDougall, Andrew S. and Roy Turkington. “Are invasive species the drivers or passengers of change in degraded ecosystems?” Ecology 86 (2005): 42-55. 4. Mack, Richard N., Daniel Simberloff, W. Mark Lonsdale, Harry Evans, Michael Clout and Fakhri A. Bazzaz. “Biotic invasions: causes, epidemiology, global consequences and control.” Ecological Applications 10 (2000): 689-710. 5. Shea, Katriona and Peter Chesson. “Community ecology theory as a framework for biological invasions.” Trends in Ecology and Evolution 17 (2002): 170176. TEACHING ABOUT INVASIVE SPECIES – PERSPECTIVES