Unit 5: Predicting the Effects of Climate Change on Soil Loss
Students will investigate how the factors that influence erosion work together to produce an overall erosion rate. In agricultural areas, these factors are rainfall-runoff erosivity, soil erodibility, slope characteristics, and agricultural practices. Students will analyze changes in precipitation predicted by climate change models to consider how a changing climate could influence erosion rates in agricultural areas.
Unit 5 supports the following overarching goals of the Growing Concern Module:
Use geological data to develop a plan for sustainable soil management in one or more agricultural settings.
Predict, using systems thinking, agricultural challenges that might result from climate change.
By the end of the unit, students will be able to:
Explain how rainfall and runoff erosivity, soil properties, landscape characteristics, and agricultural practices contribute to soil erosion.
Differentiate between natural and human influences on soil sustainability.
- Analyze, using systems thinking, how changes in precipitation predicted in climate change models for their region will impact erosion rates.
This unit directly supports multiple InTeGrate guiding principles. It encourages students to use systems thinking to investigate interactions between variables called factors that contribute to soil erosion and to evaluate how these factors could be affected by climate change. The grand challenge of sustainability is addressed through consideration of soil erosion, which is inherently interdisciplinary, as it involves the influence of both natural (geologic) processes and human (agricultural) activity and decision-making.
Context for Use
This unit builds on concepts presented in units 1-4 of the Growing Concern Module, but could also be implemented as a stand-alone unit. It is designed for use in a 50-minute class period. Students are required to complete a homework assignment prior to this class period to prepare for the first activity. Instructors with more class time may choose to have students work on the homework in class prior to beginning the first activity. This unit is appropriate for a variety of class sizes. as students work in small groups on both activities. The physical classroom setting must be able to accommodate students working in groups of four during the first activity.
Description and Teaching Materials
In this unit, students begin by completing a homework assignment to prepare in advance. In class, they first work in cooperative learning groups to share what they learned from the homework with the rest of the class. Next, they participate in a guided lecture facilitated by the instructor. Finally, they complete a follow-up homework that allows them to synthesize what they have learned.
Pre-work (before class)
Each student will complete a reading, then answer questions provided on the Pre-work for Unit 5 student page. Students will investigate one of four different factors that influence erosion rates. They will bring their responses to the discussion questions and use this information in an in-class activity.
The instructor will need to assign students to one of the four factors in roughly equal numbers.
The four assigned topics are:
- Rainfall and runoff erosivity (R factor)
- Soil properties (K factor)
- Landscape characteristics (LS factor)
- Agricultural practices (C and P factors)
Note: These factors are based on the Revised Universal Soil Loss Equation (RUSLE) defined by Renard et al. (1991), where:
Estimated average soil loss (tons/acre/year) = R*K*LS*C*P
- R = rainfall-runoff erosivity factor
- K = soil erodibility factor
- LS = length slope factor
- C = cover-management factor
- P = support practice factor
Guided lecture and activities (50 minutes)
The in-class portion of this unit is a guided lecture that intersperses active learning activities throughout. The instructor can use the provided presentation (PowerPoint 2007 (.pptx) 3.4MB Jul30 14) to guide the class period. Instructions are provided in the Notes section of the Powerpoint slides and an outline of the guided lecture is included below.
- Slide 1: Overview and learning objectives
- Display as students enter the classroom
- Slides 2-3: RUSLE homework follow-up small group activity (15 minutes)
- Students will divide into groups with classmates who had the same factor. The size of the groups is up to the instructor; four or five students is recommended. Students will compare answers from their homework and work together to address any questions that arise. Once students have discussed their answers and reached consensus, one group for each factor will present information about their factor to the class and list any remaining unanswered questions. If there were multiple groups for each factor, each group for a given factor should get a chance to add comments and questions. If desired, the instructor can record key ideas on the board as the groups present to provide a visual reminder students can refer to throughout the class period. Once all of the factors have been discussed, the instructor will summarize the key information for each one and address any outstanding questions before moving on.
- Slides 4-6: Using the RUSLE (5 minutes)
- In this set of slides, students will consider how the factors work together to produce a rate of soil loss. Two short thought problems are provided that can be used for quick think-pair-share discussions.
- Slide 7: Human activity vs. natural processes activity (10 minutes)
- This activity gets students moving around the room and allows them to consider whether factors are influenced by human or natural processes, or both. The activity is structured like the classic "getting to know you" game in which participants are asked to make a choice and move to a designated space indicating their choice. In this case, you should designate one space for human activity and another for natural processes. Opposite sides of the classroom work well. If it is difficult to move around your classroom, you could also use clickers, index cards, or a show of hands.
- How it works:
- Tell students that when each component is revealed, they must decide if they think it is influenced more by human activity or by natural processes, then move to the designated space.
- Advance the slide to reveal the component and corresponding photo, remind students what it means, and tell them to move to the designated space.
- Once everyone has made their choice, have students explain to a neighbor their reasoning for choosing that side. Then ask for a few volunteers from each side to share with the whole class.
- Clear up any confusion or ideas that need to be addressed before moving on to the next component. Note: Many components are influenced by both so there is no single correct answer. Students should be encouraged to consider multiple processes that can impact the same thing.
- Expected answers:
- Support practices (human)
- Soil porosity (both: texture, organic matter, and biological activity are examples of natural processes; tillage and driving machinery are examples of human activities; these are introduced in the Unit 2 homework)
- Slope steepness (mostly natural, except in areas where terracing is a common practice)
- Surface roughness (both: Tillage can increase surface roughness up to a point when clods are broken up too much; rainfall causes depressions to fill with sediment and decrease surface roughness over time)
- Rainfall intensity (natural)
- Use rainfall intensity as a transition to the next section on impacts of climate change by asking students what controls rainfall (climate). End with the idea that climate change influences natural processes such as rainfall and heightens the need for human action. The video in the next slide discusses this idea in the context of agriculture.
- Slide 8: Climate change and agriculture video: "Science for a Hungry World" from NASA (5 minutes)
- The video addresses the effects of increasing atmospheric CO2 on plant growth, discusses decreasing crop yields with increasing temperatures from a global perspective, and ends with a bit about how NASA satellite data in gathering this type of data. Before starting the video, the instructor should ask the class to predict how global climate change might impact agriculture.
- Slide 9: Local impacts of climate change
- It is important to help students bridge global (as presented in the video) and local impacts of climate change. Use the map of modeled changes in precipitation for North America to have students determine one predicted impact in their local region.
- Slides 10-12: Introduction to systems diagrams
- This series of slides links the idea of changing precipitation patterns back to soil sustainability. The RUSLE allows us to calculate changes in erosion, but a systems diagram (presented in Slide 12) allows for a more nuanced investigation of the mediating processes that link precipitation and erosion.
- Slides 13-22: Interpreting systems diagrams
- This series of slides walks students through each component of the systems diagram and explains how to interpret the relationships indicated by the various symbols. The headings are written so that students can review them on their own if needed.
- Slides 23-25: Example
- These slides give students a chance to practice using the systems diagram by considering data from a particular region (in Nebraska) and how the same climate change effects (decrease in precipitation) can have different effects on erosion when you consider the needs of the plants themselves.
- Slide 26: Wrap-up
- In the corn/wheat example, students see that a change in the system can impact individual crops in different ways. What is planted and the management practices employed are ultimately human decisions that have a big impact on the agro-ecosystem. This slide of the U.S.-Mexico border is provided as an example of how economics and politics also affect the agricultural system. You can use this to guide a closing discussion about the idea that sustainable solutions to mitigating the impacts of climate change must address environmental, social, and economic factors.
In the homework, students will synthesize what they have learned in this unit and practice using systems language to describe relationships in the system under investigation.
- Powerpoint for Guided Lecture (PowerPoint 2007 (.pptx) 3.4MB Jul30 14)
- Climate change and agriculture video: Science for a Hungry World (produced by NASA) (MP4 Video 54.7MB Aug9 13)
- Lecture Notes Handout (MS Word version) (Microsoft Word 2007 (.docx) 3.1MB Sep18 14)
Lecture Notes Handout (pdf version) (Acrobat (PDF) 911kB Sep21 14)
- Unit 5 Follow-up Homework (MS Word version) (Microsoft Word 2007 (.docx) 38kB Sep18 14)
Unit 5 Follow-up Homework (pdf version) (Acrobat (PDF) 107kB Sep21 14)
- Zip File With All Unit 5 Files (Zip Archive 62.6MB Jul31 14)
Teaching Notes and Tips
The activities in this unit require students to work cooperatively to consider complex issues from a systems perspective. This may be new for some students, and they may need more guidance from the instructor than is provided on the handouts. These activities are intended to give students a chance to think through the concepts on their own, so some of the questions are intentionally open-ended with multiple "correct" answers. It is important for the instructor to circulate and help students as they are working to alleviate frustration that can occur as a result of this type of work.
The follow-up homework is intended to be used as a summative assessment for this unit.
Links to answer keys for the pre-work and homework assignments are provided below.
References and Resources
- Montgomery, D. R., 2007, Soil erosion and agricultural sustainability: Proceedings of the National Academy of Sciences of the United States of America, v. 104, no. 33, p. 13268-13272.
- Pruski, F. F., and M. A. Nearing, 2002, Climate-induced changes in erosion during the 21st century for eight U.S. locations, Water Resour. Res., 38(12), 1298, doi:10.1029/2001WR000493.
- Renard, K. G., Foster, G. R., Weesies, G. A., and Porter, J. P., 1991, RUSLE - Revised Universal Soil Loss Equation: Journal of Soil and Water Conservation, v. 46, no. 1, p. 30-33.
- Wilkinson, B. H., and McElroy, B. J., 2007, The impact of humans on continental erosion and sedimentation: Geological Society of America Bulletin, v. 119, no. 1-2, p. 140-156.