This modeling activity simulates how atmospheric CO2 concentrations, which influence global climate, increase with deforestation and decrease during reforestation. As fast-growing tropical trees sequester carbon via the process of photosynthesis, carbon also cycles through trees, soil, animals, and back to the atmosphere via respiration and decomposition. Students gain hands-on experience in exploring carbon cycling, and linkages with nutrient cycling and food chains. The quantitative aspects of this activity promote integration of mathematical skills with scientific concepts. The model is downloadable (PC’s only, ExtendSim software, ImagineThat, Inc.) for free at: www.nrem.iastate.edu/ECOS/rfsims.html. This animated, interactive, game-like, bilingual model of a tropical rainforest contains an instructional video, a tutorial-like ‘lesson pane’, and four Levels with different ecological concepts and levels of complexity. Concepts include the law of conservation of matter in relation to carbon cycling between land and atmosphere. Three ‘state’ variables — sunlight, rain, and nutrients — are adjustable, as is land use, which toggles between pasture and forest in Level 4. Food webs and detrital fluxes are portrayed within an ecosystems context, such that biodiversity declines as habitat becomes degraded. Storages and fluxes are animated with icons to provide a visual sense of the model’s quantitative basis; actual quantities are provided in spreadsheet and graphic form. Students can thus engage actively in the scientific method by posing questions and formulating hypotheses. They can gather data from running the model at different experimental levels of the state variables to test hypotheses, evaluate the data collected, and present results in essays, posters, or Powerpoints.

This material is based on work supported by the U.S. National Science Foundation (Grants DEB 0703561 and 1119223). The simulation model was used in the 2008 Fairchild Challenge: http://www.fairchildgarden.org/education/fclinks/rainforestmodel/.