Over the last decade the concept of ecosystem services such as filtration, regulation, pollination, and food production have gained currency. But these ecosystem services in turn depend on even more basic biosphere processes:

• solar energy flow
• water cycling
• nutrient cycling
• community dynamics or succession

These biosphere processes provide the foundation for all sound management, and for ecosystem services such as food, fiber, fuel, mitigation of flood and drought, water and water quality, disease regulation, and recycling of wastes--without which our economy would not be able to function.

by Peter Donovan

In Allan Yeomans’s book Priority One: Together We Can Beat Global Warming (2005, 2007), he states that an additional 1.6% of the top 12 inches of the world’s cropland and grazing land soils turned into organic matter would bring atmospheric carbon dioxide concentrations below 300 ppm (if we also quit adding carbon to the atmosphere). This figure is based on removing 80 parts per million of atmospheric CO2.

Yeomans’s calculation converts carbon to soot (Priority One, chapter 2). Here is a somewhat more straightforward calculation. Note that the figures are for straight carbon, not carbon dioxide.

The atmosphere currently contains about 800 Gt (gigatons or billion metric tons) of carbon. The vast majority of this is in the form of carbon dioxide, which is currently about 383 parts per million (Yeomans used 380 ppm for his calculation). Each of these parts per million = 800/383 = 2.089 Gt C. So, to take out 80 ppm we are talking about removing 80 x 2.089 or 167 Gt (167,000,000,000 metric tons) of carbon from the atmosphere.

Soil density is usually between 1.2 and 1.4 on a dry basis. That is in relation to the density of water which is 1.0.

A hectare of soil (100 m x 100 m), 12 inches or 30.48 cm deep, has a volume of 3,048 cubic meters. At a soil density of 1.2, this foot-deep hectare of soil weighs 3,658 metric tons. One percent of this weighs 36.58 metric tons, and if this 1 percent is organic matter (58% carbon by weight), it contains 21.21 tons of carbon.