Place-based instruction allows students to explore learned concepts while building emotional connections with the location in which they are studying. Furthermore, the case for experiential science education continues to grow, and such pedagogy may be particularly beneficial to learning in ecology and environmental science. We present an experiential, place-based pedagogy aimed at introducing international high school or undergraduate students to the concept of biological invasions. Our lesson began by introducing our class, a group of Chinese high school students in a summer program in the United States, with examples of invasive species that had previously been introduced from China into the United States or vice versa. Guided discussion then focused on plant and animal species with which the students had some familiarity and covered concepts of biological invasions more generally. Next, students participated in a field activity exploring the ecology of the invasive tumbleweed Salsola tragus, a Eurasian (including much of China) species that has invaded the United States. Through classroom and field activity, students gained understanding of biological invasions, and we believe that internalization was enhanced by connecting the lesson with students' own experiences and participation in basic scientific methods and ecological fieldwork.
Bridging the gap between what can be learned in the classroom and the natural environment represents a hurdle to many educators. Place-based instruction allows students to experience the natural world through exploration of learned concepts while building an emotional connection with the location in which they are studying. When successfully implemented, place-based instruction deepens students' understanding of classroom-learned concepts by providing a dynamic working context for the scientific knowledge (Semken & Freeman, 2007). Moreover, cross-cultural place-based instruction has been suggested as a pedagogical instrument to enable international students to learn about topics through a focus on examples closely tied to their own experience and place (Smith, 2002).
A related pedagogical concept that also aims to connect classroom instruction and practice is experiential learning, which emphasizes hands-on activities in classrooms and laboratories where students “learn by doing” or otherwise experience course content firsthand. Experiential learning has long been considered a cornerstone of successful environmental education (Cummings, 1973). Indeed, the benefits of experiential learning in the fields of ecology and environmental science have been documented, as research has demonstrated considerable influence of childhood interaction with the natural environment – through play and other experiences – on environmental perspectives as an adult (Bixler et al., 2002; Ewert et al., 2005), and experiential learning has been a cornerstone of the development of ecological literacy and related perspectives (reviewed by McBride et al., 2013).
Here, we present an example that combines place-based and experiential learning to bridge cross-cultural differences between instructors from the United States and high school students from China. The international STEM (iSTEM) program at Texas Tech University was developed when the lack of rural, untouched space in the large metropolitan areas of China prompted high school science teachers to look for opportunities for their students to gain experience interacting with environmental sciences and natural resources outside of the classroom and learning to conduct hands-on research. The iSTEM program was designed for students to come to the United States for three weeks and to work with faculty and explore a new discipline within the environmental sciences daily. In 2014, the 11 student participants were from a large, academically rigorous boarding school that teaches classes in English and Mandarin, so the students were used to learning complex concepts in English.
We began this activity with approximately two hours of class instruction followed by three hours of guided activity in a field-based lab. The classroom lesson began with the introduction of several examples of invasive species that had previously been introduced either from Asia into the United States (e.g., emerald ash borer [Agrilus planipennis] and Russian thistle [Salsola tragus]) or from the United States into Asia (e.g., American bullfrog [Rana catesbeiana] and prickly pear [Opuntia stricta dillenii]). After beginning the lesson by focusing on plant and animal species with which the students had some familiarity, we covered concepts about biological invasions more generally. The following day, students participated in a field activity exploring the ecology of the invasive tumbleweed Salsola tragus Linnaeus, a Eurasian (including China) species that has invaded much of the United States. Overall learning objectives were for students to
define the terms biological invasion and invasive species,
connect biological invasions to their own experience,
understand mechanisms by which invasive species impact their environments and list common characteristics of successful invaders, and
experience basic scientific methods and ecological fieldwork.
Background Information (Classroom Discussion)
The term biological invasion describes the process through which species establish populations beyond their historical native ranges and negatively affect their novel surroundings. Impacts of biological invasions include disturbance of native communities and nutrient cycles, disruption of agriculture and other human land uses, and threats to human health (reviewed by Mack et al., 2000). Invasive species rank among the most important drivers of global biodiversity loss (Bellard et al., 2016), and Pimentel et al. (2005) estimated that the economic costs of biological invasions total $120 billion annually in the United States alone. Thus, increasing understanding and management of biological invasions represents a critical global challenge, and numerous recent publications have explored how to introduce this topic into high school and undergraduate classrooms and laboratories (e.g., Hewitt et al., 2014; Lampert, 2015; Poppenwimer et al., 2015).
The economic growth of China over the past several decades has led to an increase in trade with the United States, and with that increase in trade has come an increase in opportunities for movement of invasive species (Ding et al., 2008). Because our class consisted of Chinese high school students visiting the United States, we used the movement of species between China and this country as a platform to introduce the concept of invasive species by identifying species that our students could have previously encountered.
Thus, our classroom lesson began by dividing the class into groups of three or four students each and having them use web searches to generate short oral reports on salt cedar (Tamarix chinensis) and emerald ash borer (plant and animal species, respectively, that have been introduced from Asia into the United States) as well as prickly pear and American bullfrog (plant and animal species, respectively, that have been introduced from the United States into China). In their reports, groups were instructed to identify where in the world these species are known to occur and how they impact their environment. Following group presentations, guided discussion led to the revelation that each of these is an invasive species. We then covered topics such as the invasion process, impacts, and management. We introduced a field laboratory exercise designed to study the ecology of S. tragus, a plant that our students recognized from China.
Originally native to much of Eurasia, S. tragus has invaded disturbed landscapes throughout much of the western United States, where it is known to “tumble” with the wind across open rangelands and plains. Its widespread distribution, well-understood habitat requirements, and invasive nature make it a useful teaching tool. It is mostly shade-intolerant and can be found in arid and semiarid habitats worldwide (Howard, 1992). In the shortgrass prairie around Lubbock, Texas, it colonizes open and disturbed soils and can especially increase during drought and after activities that disturb the existing vegetation (Hyder et al., 1975), when it can detrimentally impact native prairies by increasing native plant mortality through competition for soil moisture (Allen, 1982).
Application (Field Activity)
We guided students in a field laboratory exercise during which they collected data to determine where invasive tumbleweed is most likely to be found. We had success with students working in small groups of four or five, with instructors floating between groups to help troubleshoot any issues that came up. Required supplies included a 50 m transect tape, a 0.5 m2 quadrat made of PVC or other lightweight and durable material, and a 1 m ruler. Groups began by spreading out on the landscape and marking two 50 m transects each, with one transect occurring in an undisturbed area and another occurring in a disturbed area (in our case, a roadside regularly mowed with a lawnmower).
Groups conducted a 1 × 50 m belt transect survey (for easy-to-understand methods, see Herrick et al., 2017) to count the number of tumbleweeds within 1 m of the transect tape, making sure to record their observations on pre-prepared data sheets. Next, groups used Daubenmire quadrats (Daubenmire, 1959) to estimate the amount of bare ground present along transects to the nearest percent. To do so, each group started by placing the quadrat on the ground at meter no. 1 of the transect. Within the quadrat, students estimated the percentage of the ground surface that was occupied by bare soil. After recording their estimate, the group moved their quadrat 2 m down their transect (i.e., to meter no. 3) and repeated this process for a total of 25 observations along each (i.e., undisturbed and mowed) transect. Finally, either concurrently with previous quadrat measurements or as a separate measurement taken along each transect, groups measured the vegetation height at the lower corner of each quadrat (n = 25 observations per undisturbed and mowed transect) on their data sheets.
After collecting the data, we provided pre-formatted spreadsheets on a shared laptop to streamline student data entry into a single file that ensured that data were entered in the correct format for importation into graphing and analysis software (in our case, R; R Foundation for Statistical Computing, Vienna, Austria), and statistical analyses were performed by the instructors during the class period. Statistical analyses included a t-test to compare tumbleweed density in undisturbed vs. mowed habitats. We also performed analysis of variance (ANOVA) to compare the amount of bare ground as a function of habitat (undisturbed vs. mowed) while considering student group as a statistical block to account for between-group variation in estimation of bare ground. Finally, we also used ANOVA to determine whether vegetation height differed between undisturbed vs. mowed habitats, again blocking by student group. In our implementation, we employed an arcsine square root transformation to increase normality of bare ground data, which were estimated as percentages. In addition to performing statistical tests and briefly introducing the purpose and interpretation of these tests to our class, we also visualized results using box-and-whisker plots.
The impacts of invasive plants on ecosystems have been well documented across time and ecosystems (Vilà et al., 2011), and even simple high school or undergraduate class activities like ours have the potential to contribute to the overall understanding of plant invasions. Regarding tumbleweed invasion, we found that tumbleweed density was 36.0 ± 17.0 plants per transect (mean ± SD) in mowed habitat vs. 11.4 ± 16.6 in undisturbed habitats, and this difference was statistically significant (P = 0.048; Figure 1A). Possibly explaining this difference, ANOVA indicated a significant effect of habitat (P < 0.001) on bare ground, with 49.7 ± 29.3% bare ground in mowed habitats vs. 19.1 ± 24.2% in undisturbed habitats (Figure 1B). No team effect was observed in bare ground measurements (P = 0.6091). We did observe a team effect on height measurement (P = 0.002), but height itself also significantly differed between disturbed (4.3 ± 5.8 cm) and undisturbed (48.1 ± 44.6 cm) habitats (P < 0.001; Figure 1C). The class then brainstormed explanations for our observations, and students' ideas included (1) that the disturbance of mowing creates conditions in which the tumbleweed can more easily establish invasive populations; and (2) that the presence of the tumbleweed contributes to the overall disturbance and excludes native species.
Following analysis and discussion of specific results, class wrap-up discussion helped draw connections between the field activity and concepts learned in the classroom. Furthermore, we found that this final discussion provided an opportunity to pose questions that challenged students to apply learned concepts to their own place and experience. Discussion questions for our class included
Do you think you would find the same results about tumbleweed if you did this same activity in your region of China? Why or why not?
What should we do here in Lubbock to prevent Tumbleweed from further invading native habitats? Do you think the same would apply to China?
Do you think it is important to share what you've learned about biological invasions with others? How will you do this?
Place-based and experiential instruction have been considered of growing importance in science classrooms, and these pedagogies may have particular benefits in learning and meaning when paired with cross-cultural applications in ecology and environmental science. The lesson plan presented here is designed to introduce students to the concepts of biological invasions in a culturally significant way. It provides international students with an introduction to practice in field ecology and allows them to connect simultaneously with their current local place and their country of origin through international examples of invasive species (i.e., plants and animals that had, similar to the students themselves, traveled from China into the United States as well as vice versa) to maximize the perceived relevance of the activity and topic.
Our class consisted of high school students from China, but this activity could be adapted to serve younger, domestic, and/or low-socioeconomic audiences in any science classroom with just a few basic tools, allowing students to research invasive species from a country of their choice. While we conducted the activity in a specific field laboratory, any large open area, such as a park or field, could be used to replicate this experience in a very cost-efficient way. Additionally, the identification of appropriate statistical tests and experimental design could be incorporated for advanced students. More detailed comparisons for the field component of this lesson could include calculating the number of species in each trophic level for each habitat and comparing measurements among additional diverse habitats.
Unfortunately, biological invasion is a global phenomenon and continues to grow (Seebens et al., 2018), so selecting culturally appropriate examples to relate to students from other parts of the world should be straightforward. Online databases curated by the U.S. Geological Survey (https://nas.er.usgs.gov/) and the Invasive Species Specialist Group (http://www.issg.org/) can also be used to adapt this activity to another country or region of the United States. This activity could also be conducted in local community gardens or parks, where students could study and document the damage or presence of invasive species. This activity could also be modified in partnership with local stakeholders such as Border Patrol, National Park Service, and other professionals who regularly have to deal with the risks and effects of contamination and invasive species.
Finally, although we have described a lesson emphasizing the impact of biological invasions, the activity described could be amended such that it does not focus on any specific target a priori and instead aims to measure the differences in grass, herb, and shrub densities in mowed vs. unmowed areas, grazed vs. ungrazed, burned vs. unburned, and many others. In this way, our flexible activity can be adapted to provide place-based and experiential learning not only about biological invasion, but also about habitat loss, disturbance, and many other elements of global change.
This activity was hosted by Texas Tech University STEM Center for Outreach, Research & Education (STEM CORE) and the Texas Tech University Department of Natural Resources Management. Thanks to Dr. Jerry Dwyer for encouragement to put this lesson together. Mark Johnson assisted with instruction during the field activity.