Undergraduates in ecology and conservation biology courses often lack a clear understanding of how to do fieldwork and utilize data analysis to answer complex questions. This is unfortunate, because with proper training these students could identify and address some of today's most pressing environmental issues. I present a simple, problem-based learning activity that provides students a new approach to understanding two important topics in the environmental sciences – how biodiversity is distributed across landscapes and how habitat loss can affect this biodiversity. This activity helps students explore foundational concepts in biology, enables them to collect data in a simplistic field setting, and introduces them to statistical analyses and modeling. In addition, it also teaches students how to ask questions, synthesize data, and address an issue using the same approaches that conservation practitioners utilize in the real world.
Courses in ecology and conservation are well suited to give students the skills necessary to address a broad range of environmental issues facing our world (Cid & Pouyat, 2013; Schaefer & Gonzales, 2013; Lewinsohn et al., 2015). However, students often lack basic scientific literacy and an understanding of the methodologies employed by practicing scientists (Jordan et al., 2009; AAAS, 2011; Pool et al., 2013). To address these shortcomings, a multifaceted educational approach is required that integrates background readings, hands-on activities, and data analysis/synthesis.
One specific approach that can help meet this goal is utilizing problem-based learning (PBL) activities. PBL activities are student-centered approaches that increase student knowledge of content and critical thinking through the use of instructor-facilitated problem-solving exercises (Barrows, 1996; Wood, 2003; Barrett, 2010; Schmidt et al., 2011). For each activity, students are presented with observations or problems and then participate in structured and self-directed programs that include background reading, collection of data, and synthesis of results (Barrows, 1996; Wood, 2003; Gijbels et al., 2005; Barrett, 2010; Schmidt et al., 2011; Prosser & Sze, 2014). To date, this approach has become increasingly utilized in ecological education, and there is growing evidence that it increases retention of knowledge and reinforces higher cognitive skills (Hoover et al., 2012; Cardelús and Middendorf, 2013; Schaefer & Gonzales, 2013; Bestelmeyer et al., 2015; Lewinsohn et al., 2015).
Here, I present a novel PBL activity I have incorporated into my conservation biology and ecology courses. This activity helps students increase their understanding of ecological theory, the basics of fieldwork, and data analysis. In addition, it addresses two key concepts in environmental sciences – how biodiversity is distributed across landscapes and how habitat loss affects biodiversity.
Background & Approach
Sampling biodiversity in an ecosystem is challenging for students because expertise is required in field methodologies and species identification. In addition, sampling across ecosystems poses substantial challenges because of time constraints. Therefore, we must design simplistic approaches that help students better understand the fundamental concepts behind fieldwork and how the data we collect can help us make predictions about how the world works.
A second challenge for students in environmental courses is determining how habitat loss affects biodiversity. While habitat loss poses a significant threat to biodiversity worldwide (Brooks et al., 2002; Sax & Gaines, 2008; Pimm et al., 2014), predicting which species will go extinct from habitat loss is often difficult (He & Hubbell, 2011). For example, there have been 785 documented extinctions worldwide to date (Sax & Gaines, 2008; IUCN, 2015), but estimates of undocumented extinctions generally far exceed these numbers and can be as high as 27,000 per year (IUCN, 2015). As a result, reconciling these differences is often challenging for instructors and students alike (Novacek, 2008).
To address these two shortcomings, I have created a simple activity that teaches students about biodiversity and how to predict how biodiversity is affected by habitat loss. This activity can be done in either a field setting or outside of a building where class is held. Below, I detail how this study can be conducted using a problem-based learning approach or in a typical instructor-led activity. In addition, I discuss two potential graphs that could be used to help students analyze their data.
PBL & Instructor-Led Approaches
Prior to class, students will be given a set of background readings, with two observations/problems, and a list of the supplies they will be using (see below). Using this as a guide, instructors should let students know that they will be working in class to design a simple simulation study that can be used to address these two issues.
Once in class, students will begin the activity by breaking into small groups and discussing why species' distribution patterns may differ for different species and in different ecosystems. In addition, they should discuss how biodiversity can be effectively sampled for and how habitat loss is likely to affect biodiversity in different ecosystems. Depending on the nature and level of the class, this activity can be either student or instructor led. To help facilitate this discussion, I have created a glossary of important terminology that can be examined by students (Appendix).
Using the discussion above, the list of materials that students have been given ahead of time, and the terms in the Appendix, students will work with instructors to design a study using jelly beans that can be distributed across a landscape in different ways to simulate the distribution of biodiversity across space. Specific considerations to make are what types of distribution patterns jelly beans will be placed in and what types of species these jelly beans will simulate.
Using the approach designed above, students will disperse variety packs of jelly beans across a study area to simulate how “species” are distributed across a landscape. Flavors of jelly beans represent different “species,” so keep the jelly-bean packages to use as “species identification guides.” How jelly beans are distributed across the study area can be determined in conjunction with students or to suit the purpose of the lesson (e.g., examining the differences between random, regular, and clumped distribution patterns).
Using the background readings described above, students and instructors can design an effective sampling methodology for determining how species are distributed across their habitat. The most simplistic approach for this is to have student groups establish a transect line that goes through the area where the jelly beans are distributed (Figure 1). This will create a subsection of habitat, which can be sampled to determine the number of “species” and their abundance.
Following the placement of transects, students can utilize a quadrat sampling method of their choice to sample for “biodiversity” (i.e., count the number and type of jelly beans they find). Two simple approaches for students are to place a PVC quadrat or hula hoop at set or random intervals to sample plots (Figure 2)
Students will use the jelly-bean package as their “species identification guide” and determine how many individuals of each “species” were observed in the plots.
Following collection of data, students will use sidewalk chalk or a white board in the classroom to create graphs about the data they collected (Figure 3; see sections on graphs 1 and 2 below for more details on instructor-led graphs). This method of analysis can be led either by students or by instructors using the two potential graphs below. In this portion of the activity, instructors should challenge students to think about three main things: (1) What is the relationship between the number of species and the area sampled? (2) Are some species rarer or more dominant than others? (3) How could you use the information collected to determine the effects of habitat loss on biodiversity?
Finally, students and/or instructors could engage in a quick wrap-up discussion about the exercise as a whole. Topics to be discussed in this portion of the activity could include (1) what the advantages are of using jelly beans versus other materials (e.g., nonbiodegradable items such as plastic beads) and (2) how model species such as these jelly beans have been used historically to understand species distributions and interactions (e.g., Calver & Wooller, 1998).
Species are distributed unevenly across landscapes, which makes it difficult to determine which are abundant and which are rare.
Habitat loss is a significant threat to biodiversity, but predicting actual losses of species resulting from this land-use change is often difficult.
Brown, J.H., Mehlman, D.W. & Stevens, G.C. (1995). Spatial variation in abundance. Ecology, 76, 2028–2043.
Pimm, S.L. & Raven, P. (2000). Extinction by numbers. Nature, 403, 843–845.
Connor, E.F. & McCoy, E.D. (2001). Species–area relationships. Encyclopedia of Biodiversity, 5, 397–411.
World Wildlife Fund (2016): http://wwf.panda.org/about_our_earth/biodiversity/biodiversity/
Variety package of jelly beans for each student group
Transect tapes for establishing sampling area
Premade PVC quadrats or a hula hoop for sampling plots
Graph 1: Frequency Distribution across Space
A key concept for students to grasp is that species vary in abundance and that in many habitats there are rare and dominant species. To help students understand this, instructors could task each group with creating a frequency histogram showing how abundances of individual “species” vary across the plots they sampled. This graph is often referred to as a rank-abundance chart or a Whittaker plot. To make this graph, the following information should be utilized. (1) The x-axis is the abundance by rank, which means that the individual flavor of jelly bean (aka the “species”) with the most individuals is number 1 and the second-most-abundant is number 2. (2) The y-axis is the abundance (i.e., the number of individuals found for each “species”). For a visual depiction of how this graph could look, see Figure 4.
Key Concepts to Discuss for Graph 1
Through this graphing exercise, instructors can discuss species distributions, rarity, and dominance. These are essential concepts for students to get in ecology and conservation biology courses and will serve as a natural segue for discussions about habitat loss. For more information on each of these terms and how they could be included in discussions, see Appendix.
Graph 2: Species-Accumulation Curves
A common tool that biologists use to estimate how effective their sampling has been at capturing biodiversity is a species-accumulation curve. To graph this curve, students can utilize the following information: (1) x-coordinates will represent the number of plots sampled; (2) y-axis values will range from zero to the total number of “species” collected across plots; and (3) each point will correspond to the total number of unique “species” found within individual plots as sample size increases. For example, if you sample the first plot and find two types of jelly beans – your first x, y coordinates will be 1,2; and if you sample the second plot and find 3 types of jelly beans, but 1 is the same from the first plot – your second x,y coordinate will be 2,4 (for more information on this graph, see Figure 5).
Key Concepts to Discuss for Graph 2
After creating the second graph, student groups can explain the patterns they observed and discuss any differences in trends between groups. In addition, instructors can introduce concepts such as species saturation and asymptotic sampling curves, and lead discussion on whether these patterns should hold in all ecosystems around the world or for all taxonomic groups. For more information on each of these terms and how they could be included in discussions, see Appendix.
Predicting Habitat Loss & Its Impacts Using the Two Graphs
A key challenge in education is helping students take the data they have collected and analyzed and use it to make predictions. For this final analysis, instructors can introduce students to the concept of habitat loss and discuss how it can alter frequency distributions and species-accumulation curves. For instructors, the easiest ways to get this idea across are to (1) have students randomly remove a number of the plots from their data and reanalyze the revised dataset and/or (2) have them erase a portion of graph 2 (e.g., plots 6–10 on the x-axis) and then discuss how this loss of habitat affects their biodiversity patterns. Finally, instructors can also discuss how conservation biologists use these same techniques to make predictions about what will happen to real-life ecosystems affected by habitat loss.
This activity is designed to promote an increased understanding of biodiversity and how it can be affected by habitat loss. Because of its flexible nature, it can be student-led using a PBL approach or in a more traditional, instructor-led setting. This activity is particularly useful because it helps introduce students to field data collection, graphical analysis, and predictive modeling. Furthermore, by engaging students in this manner, instructors can hope to help increase knowledge retention and reinforce important concepts that are at the core of conservation biology and ecology. Finally, by helping teach students how to ask questions and analyze data, instructors will be making important strides in helping to give students the skills necessary to address environmental problems in the future.
I would like to thank the undergraduate students in my classes for helping me experiment with this problem-based learning approach.
List of important terms and definitions that could be used for discussion activities, with brief mentions of how many of the terms may specifically apply to this activity.
Abundance – The number of individuals of a species found in a given area. In this activity, abundance could be measured as the number of individuals of each flavor of jelly bean.
Asymptotic Sampling Curves – This is also referred to as a rarefaction curve and represents the curving that takes place when you sample more areas to look for more species. At first, you find many more species, but after substantial sampling, you tend to level off and only find the rarest species. In this activity, this is the pattern we expect to observe when sampling for “species” using jelly beans because there are only a set number of jelly beans that exist. In nature, we expect this pattern to occur because organisms must have specific traits and characteristics to survive in a habitat and not all organisms can persist in all environments.
Biodiversity – This term is often defined differently, but here it is defined as a measure of the variety and variability of “species” in a given habitat.
Clumped Distribution – This is the most common distributional pattern in nature. In this case, individuals/species are found in close proximity to each other, often corresponding with the distribution of resources. An example of this could be the distribution of amphibian species around ponds in a forested landscape.
Dominance – This refers to the degree to which a species is more numerous than its competitors. In the present study, the species with the most individuals are the most dominant.
Evenness – This term discusses how species vary in abundance within habitats. Habitats that have more even distributions are ones that have similar numbers of individuals for all species. Uneven habitats are ones where some species are significantly more dominant than others.
Habitat Loss – This refers to the process whereby habitat is lost or converted from its natural form. In this activity, you can see that habitat loss can differentially affect species, depending on their distributions and abundances.
Random Distribution – This distribution pattern occurs when species/individuals found in a given environment and their position are independent of other individuals. This is the type of pattern that can occur when abiotic factors primarily affect dispersal, such as dandelion seeds being dispersed by wind.
Rank-Abundance Graphs – This type of graph can be used to visualize the differences in the abundance of different species. It is often used to determine which species are dominant in an area and which are rare. In this activity, this can also be useful for telling which species may be most likely to be affected by habitat loss.
Rarity – This refers to species that are often uncommon or infrequently encountered when sampling.
Regular Distribution – This distributional pattern is when species/individuals maximize the distance between each other and spread out uniformly across a landscape. Plants may often exhibit this pattern when species use chemicals to prevent growth of competitor species (i.e., allelopathy).
Richness – The total number of species. In the present study, this represents the total number of jelly bean “species.”
Species-Accumulation Curves – These are often referred to as species–area relationships, but they represent the number of species that are found as you increase in area sampled.
Species Saturation – This term refers to the maximum number of species that an area can support. In the present study, this concept can be discussed using the number of different types of jelly beans (i.e., species) found in the variety-pack bag.