This chapter discusses human impacts on the global nitrogen and phosphorus cycles that link the living and non-living parts of the Earth system. These chemical relationships control the general pattern of interaction between geological and biological processes. Professor Cornell uses diagrams that show present day cycles, flows between stocks, and human changes. While people are most familiar with carbon, nitrogen is also a very important element for life on Earth. Nitrogen is fixed from the atmosphere through the agricultural, industrial, and transport sectors, and has negative effects in terms of algal blooms and eutrophication. Nitrogen is transported very large distances in the atmosphere. The phosphorus cycle has also been affected greatly by human activity and contributes to nutrient enrichment.

This video is licensed under the CC BY-NC-SA license.