10 March 2007
Without stealing his “thunder,” Craig does a good job of introducing biogeochemical processes in the soil and the potential soil has for sequestering carbon. Incredibly, there is more carbon, globally, stored in soil than in the atmosphere and living vegetation combined.
Craig’s article contains a map of degraded soils worldwide. I don’t want to minimize the role of burning fossil fuels in raising atmospheric carbon dioxide over the last 100-years, but the degradation depicted in the map involves, in part, loss of soil organic matter, which has been lost from either accelerated erosion or decomposition due to regular plowing. Plowing aerates the soil, speeding the process of organic matter decomposition, and exposes the soil to erosive forces.
Oceanographers and climatologists are concerned withÂ ocean acidification. Much of the ocean acidification is due to soil carbon entering the ocean either as sediment or dissolved carbon carried by rivers.
So, you start talking about soil and soon you’re talking about the ocean and atmosphere.
What to do? The key is to use best management practices that minimize erosion. Growing perennial crops is preferable to annuals as perennials do not require working the soil and planting every year. This is one of the reasons that ethanol derived from sugar cane is more efficient than making ethanol from corn. This is why cellulosic ethanol from switchgrass or wood chips is more efficient than ethanol made from corn.
Converting to perennial root-dense grasses (like switchgrass) instead of annual row crops such as corn would also store more carbon in the ground than would be harvested as crops. This would restore some of the carbon to the soil that has been lost over the past 100 years, or so, due to tillage, oxidation, and erosion.