GEF

Unit 4   |  The Global Ecosystem 101 CHECK YOUR UNDERSTANDING 1. How old is the Earth? When did the first modern humans emerge? 2. Why can the Earth be viewed as a system? What are the four main systems, or “spheres,” that make up the Earth? 3. What are the three most important biogeochemical cycles that link the Earth’s systems together? How are humans dependent on these cycles? How do humans impact these cycles? 4. What is an ecosystem? Why is “thinking like an ecosystem” a vital component of practicing sustainability? How is an understanding of ecosystem services important for building sustainable societies? 5. How is sustainability an integrating concept? Why is systems thinking necessary and helpful for sustainability education? GROWYOUR KNOWLEDGE Biogeochemical cycles link the atmosphere, hydrosphere, biosphere, and lithosphere Earth systems. Studying these cycles not only shows the link between Earth systems, but also how human activity impacts these systems. In this activity, you will explore one of the cycles discussed in this unit. 1. Choose one of the three biogeochemical cycles explored in this unit—carbon, water, or nitrogen. Visit the National Center for Atmospheric Research Website (eo.ucar.edu/kids/green/cycles1.htm ) to review your selected cycle. 2. Identify the benefits of your selected cycle. Why is this cycle important? Make a list of several of the key benefits that you think this cycle provides to humans, plants, animals, and/or other living organisms. Your list may range from general (e.g., “helps plants grow”) to specific (e.g., “fills my rain barrel”). 3. Identify the human impacts on your selected cycle. How do humans interact with this cycle? List several examples of the ways you think humans interact with this cycle. Your list may include positive interactions (e.g., “using compost in gardens”) as well as negative interactions (e.g., “driving cars that emit greenhouse gases”).