Invasive species are a pressing threat to global biodiversity, and education about their identification, prevention, and management can play a vital role in limiting their spread and cascading impacts. Nonnative or nonindigenous species are by definition not native to an area, so if introduced, they often dominate native species due to their relative lack of predators and disease. When these nonindigenous organisms have negative environmental or economic impacts, they are considered invasive species (Moser et al., 2009) and are typically targeted for mitigation, management, or removal. The problem with invasive species is that many are not recognized by the general public and can spread in myriad ways. As with most environmental issues, prevention is far cheaper than management or eradication, but it is difficult for many students to understand the complexities of invasive species’ spread, management, and impact.

Invasive species have massive negative economic and ecological consequences, as they threaten agriculture, fisheries, and biodiversity in many ecosystems. Invasive species are estimated to cost $137 billion per year in the United States (Pimentel et al., 2000), and their impacts spur major trade entities such as the North American Free Trade Agreement and the World Trade Organization to become involved in regulating their spread (Andersen et al., 2004; Fernandez, 2008). Invasive species have many vectors for transport to new locations, including via hitchhiking on shipped goods, intentional introduction for food or ornamental reasons, hull fouling or ballast water of shipping vessels, and the aquarium trade, among other methods (Hulme, 2009; Lovell et al., 2006; Murray et al., 2014). The species’ spread could accelerate further with climate change, as geographic ranges of common invaders could expand and shipping channels could open new avenues for accidental dispersal (Beaury et al., 2020; Hellmann et al., 2008; Lord, 2017).

Beyond their economic impact, invasive species have substantial negative effects on biodiversity and change the way that native species evolve. They are a major cause of extinctions, especially among island birds, which have been wiped out by introduced animals, including cats, rats, snakes, and foxes (Clavero & García-Berthou, 2005). Invasive species may also push native species to evolve survival strategies centered around competition with the new invader rather than maximizing their fitness in their traditional environment (Mooney & Cleland, 2001). Despite the negative impact of invasive species on biodiversity, the management of these species is controversial and complicated; it inserts human decision-making into ecological processes and presents the challenge of deciding which species are likely to be harmful (Allendorf & Lundquist, 2003). There is the additional complication of lag time, as species are typically introduced several years before they become problematic, forcing managers and scientists to focus on prevention and early detection. These challenges highlight the need for education about invasive species, both to train future leaders and scientists and to help build early-detection programs utilizing citizen science and relying on public awareness.

Invasive species education

Early detection is one of the most valuable and cost-effective tools for preventing the establishment and spread of invasive species. As such, several programs in schools and for the general public have focused on raising awareness of the appearance and impact of invasives (Aloba et al., 2017; Reaser et al., 2020; Reis et al., 2013; Verbrugge et al., 2021). Some early-detection programs are using eDNA (environmental DNA, which detects trace amounts of DNA) in conjunction with citizen science to build an effective framework for catching potential invaders as early as possible (Larson et al., 2020; Reaser et al., 2020). Environmental education about invasive species is important but has been complicated by inconsistent terminology, unclear risk communication, and a lack of widespread dissemination of educational materials (Verbrugge et al., 2021), so it is essential to develop ways to clearly and effectively communicate about the threats, impacts, and management of invasive species.

Although game theory has been used in multiple ways to model the spread and impact of invasive species (e.g., Batabyal & Nijkamp, 2016; Büyüktahtakin et al., 2013), there are few examples of using games to teach the effect or management of these species. One such game was a board game developed by the University of Florida’s Center for Aquatic and Invasive Plants; it taught children the trade-offs of managing invasive species in a certain location (Aloba et al., 2017). Another board game taught middle and high school students about competition between native and invasive species as it simulated the colonization of a field by different players (Hopwood et al., 2013). Other games have challenged children to find and identify invasive seaweed (Skukan et al., 2020) and to invent and draw invasive species to learn about the characteristics that make them successful (Lampert, 2015). Although these tools are valuable, none focus on larger-scale management issues that arise in attempting to regulate and prevent the spread of invasive species through global transportation.

Gaming the global spread of invasive species

The game that I developed was designed to be both competitive and cooperative and to teach high school and college students about the cascading effects of the spread of invasive species. In short, each group or team represented an island nation, and their goal was to use their budget to protect their island from the negative effects of invasive species, with a secondary goal of minimizing the negative effects for the “world” as a whole. It does not require any specific materials or knowledge, as I have played this game effectively with both a college class on invasive species and with visiting high school seniors who had no previous background in the topic. I believe it is best suited to be played toward the end of units on invasive species, but it can stand independently as well.

Game setup

Start by dividing the class into groups of approximately three students—the number of groups doesn’t really matter other than for the length of the game. In each group, one student can be assigned as the speaker, one as the accountant to keep track of the money, and a third as the scientist who will keep track of the list of invasive species on that island. Each group is an island nation, and all group members have equal say in their group’s decisions.

All groups start with $4,000; before the game begins, they can choose to spend this money to prevent ($1,000 each), manage ($500 each), or ignore each of nine different potential invasion vectors (listed in Table 1). This is intentionally not enough money for them to be able to prevent every potential invasion vector, mimicking the choices that politicians, conservationists, and environmental officials have to make with limited resources. These amounts are not based on any economic model, but they were chosen to promote debate by ensuring that no group could just pick one simple strategy (e.g., manage every vector). Groups could also choose to try to save their money (the highest amount of money at the end wins). Allow approximately 3 minutes for discussion as groups record their choices. For this first round, students have been introduced to invasive species and know what the goal of the game is, but few additional instructions are given because the goal is for the students to learn the impacts of their decisions.

Figure 1 shows an example with five groups playing the game; the order in which the students take turns is the path that invasive species spread. Whether a particular species actually takes hold if and when it arrives will depend on both luck and how the group chose to manage or prevent the species’ spread. Each group will also get a vector card (see Online Appendix A) showing logos for each potential vector or a copy of Table 1.

Game play

It does not matter which team goes first, but the turn starts with the drawing of a card (example cards included in Online Appendix B) that shows an invasive species and the vector by which it arrived. After drawing a card, if the team had chosen (prior to the game) to prevent that vector (e.g., ballast water), then they are protected from the invader and their turn is over. If they had chosen to ignore that vector, then they lose $10,000 (or $20,000 if they got one of the “worst” invaders, which are underlined in Table 1). If they had chosen to “manage” the vector shown on the card, then they lose $1,000 (or $2,000 for one of the “worst” invaders). The invaders considered “worst” in this game are rats, feral pigs, and zebra mussels, which are among the most economically and ecologically harmful invasive species in North America. This separate category is included to highlight the importance of prioritizing management strategies.

The monetary amounts for the game were not based on actual estimates of economic impact but were chosen through several iterations of practice game play with three main goals in mind. First, the math needed to be simple enough that the focus remained on the spread and management of invasive species. Second, losses needed to be large enough to show that no matter the strategy, invasive species management is about losing the least amount of money. Finally, the “worst” invaders were included so that students would not think of all invasive species as equivalent and would need to think carefully about the vectors they focused on managing. Of course, this game oversimplifies the range of impacts invaders can have, but players could research and assign economic values for each invader if they wanted to build a more nuanced version of the game. Regardless of the invaders that become established on each island, it quickly becomes apparent (just as in reality) that invasive species are going to lose everyone money in the long run.

In addition to the loss of money, the invasive species may spread to the next team or island (see Figure 1). If the first team had ignored that vector, then the invasion spreads to the next island; if they managed that vector, they will flip a coin to determine whether it spreads to the next island. The second team handles this the same way as the first one did, losing no money and stopping further spread if they initially chose to “prevent” that vector, or losing money and continuing the spread. The first turn only ends when a team has prevented that vector or already has that invasive species. At this point, it is the second team’s turn to pick a card and repeat the process.

After each team has drawn a card at least once, you can decide to end the game or play a second or third round before totaling money to determine a winner. Additional money would not be provided if more rounds are played—only if a new game is started. When the round is complete and the game is over, each group will tally up their money (almost all will be negative), and the team with the highest amount of money (least negative amount) wins. Additionally, all of the expenses from the whole class should be added up; this is not a zero-sum game, so the whole class can do better or worse. After writing down the groups’ expenses and total expenses for the class (i.e., the “world”), you can prepare to play again.

Before this second game, give the whole class 5 minutes to talk about their strategy both within and between groups. As mentioned earlier, countries and trade organizations are involved in regulating the potential transport of invasive species and resources are always limiting, so this is a realistic scenario of global cooperation (Andersen et al., 2004). Before beginning the next game, ask the class about what they learned from the first game, what this means for invasive species management, and how they modified their strategy going into the second game. For students who are not familiar with the topic, guiding questions could include the following:

• How did you allocate your funds?
• How did the most successful groups allocate their funds?
• Did the strategies of the other groups affect your group?
• Which vector was most problematic?
• How would you change your strategy for future rounds?
• Would your strategy differ if all of the groups in the class worked together?

The second game is played the same way; tally up the team expenses and the total class expenses at the end of the game. The whole-class expenses are typically reduced in Round 2, as are most of the team expenses, though there is some variability; some groups just get unlucky, and that is worth discussing. Just as even the most clean and careful people get sick occasionally, invasive species are a problem everywhere in the world, and all we can do is stack the odds in our favor through effective prevention and management strategies.

Potential variations

This game could be modified in myriad ways to add complexity, teach additional concepts, or target different audiences. If it were the culmination of a larger unit on invasive species, then instead of using the listed vectors and cards (Online Appendixes A and B), students could research different vectors and species and design that element of the game using their own examples. Additionally, the expenses to prevent invasive species and the costs of an invasion were uniform because the goal was to highlight the vectors, challenges of management, and necessity of cooperation. However, the game could be built more around the economics of invasive species management if the costs of different prevention strategies and an invasion were different for each vector and invader.

The whole game could be scaled up to have multiple classes compete with one another to lose the least money; this could even be done within a class if each team is only one or two students. This would put greater emphasis on the collaborative aspect of the game, rather than on competition among groups. Climate change could be incorporated into the game as well if islands were split between two or three different climate zones and invasions would only be successful if the invader were suited to that climate zone. By changing the climate zone in a later round, the class could see how their islands are vulnerable to a different suite of invasive species, many of which they may not have prepared for. Finally, the game could highlight economic inequality by giving each group a different amount of money to begin with; groups with less money could prevent fewer invasive species and would lose the most money. As a result, students would see that even a small difference in the initial resources can lead to massive differences in costs down the road. By incorporating thinking outside the box and applying this thinking to the current global pandemic, this game could be easily modified to model disease ecology and public health strategies.

Conclusions and outcomes

Even after one round of this game, students were quickly catching on to concepts that they struggled to understand from lectures and readings, including the role of prevention and the importance of shipping routes. As often as prevention is discussed in relation to invasive species, being negatively affected by it (or a lack of it) in a competitive game drives home the relatively low cost and effect of prevention compared with the potential costs after an invasion. Even more striking of a difference in student understanding existed for trade patterns, which are complex to discuss and highlight the importance of in a classroom setting. In the game, when islands were continually getting invasive species transmitted to them from the island in front of them in the play order, teams got frustrated at the other groups that were not pulling their weight in terms of prevention. Each time an invasive species spread from group to group, the groups further down the line were anxiously hoping that another group would stop the spread before it got to them! This frustration could be harnessed to advocate for a more collaborative approach in future iterations of the game; if it is played multiple times (even with different variations), students could work collaboratively as a class to develop the most effective policy for all of their islands.

Beyond the anecdotal evidence described, I did not assess student understanding of these topics before and after the game. This could be done in the future, with surveys conducted before and after the game to ask students about invasive species, vectors, management strategies, and economic impacts. Additionally, students could brainstorm invasive species management strategies both before and after the activity, with the expectation that after playing the game, students will place a much greater emphasis on collaboration and prevention techniques. Even without formal assessment in my class, it was quite clear that the topic and the approach (using a game) resonated with both college students and high school seniors. Several students mentioned that it was their favorite class period of the semester, and as previously mentioned, students demonstrated a high level of understanding of the economic consequences of invasive species on future assignments. Even though there are other games that can be effective tools to teach about invasive species (e.g., Aloba et al., 2017; Hopwood et al., 2013; Skukan et al., 2020), this game is unique in that it focuses on economics and large-scale management rather than on identification and site-specific prevention and mitigation issues. My experience underlines the importance of environmental education in preventing the spread of invasive species (Verbrugge et al., 2021) and helps with the complicated issues of risk management and economics.

Joshua Lord (lordj02@moravian.edu) is a professor in the Department of Biological Sciences at Moravian University in Bethlehem, Pennsylvania.