British Petroleum Energy Calculator: How Big Is Your Carbon Footprint? Click on link to Energy Calculator
Distinguishing Abiotic and Biotic Plant Problems
Does Organic Matter Really Matter?
Farming for Carbon
The Global Carbon Cycle (animation)
The Global Nitrogen Cycle (animation)
Intergovernmental Panel on Climate Change: How Do Human Activities Contribute to Climate Change, and How Do They Compare with Natural Influences?
National Arbor Day Foundation (maps of plant hardiness zones, comparing 1990 to 2006)
National Geographic Soils Issue (September 2008)
