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How Soil Can Solve Climate Change

Posted by kevinwolz on March 11, 2012

Just ran the numbers…I’ve been meaning to do this for quite a while now…

There are 1.89 quadrilion (10^15) pounds of carbon (C) in the atmosphere (as carbon dioxide – CO2). That’s a lot. Here’s a better way to think of it…that’s about 1.2 lbs of C for every sq. ft. of land on Earth’s surface. Taking this a bit further, with ~40% of Earth’s land surface today covered by either cropland or pasture, that’s ~3 lbs of C for every sq. ft. of agricultural land – a much easier number to wrap your head around.

Those numbers are for today’s situation, with atmospheric [CO2] at about 393 ppm. Pre-industrial levels were about 290 ppm, and while it’s important that we eventually get back down to those levels, it is commonly argued by scientists that bringing [CO2] down to just 350 ppm will at least stave off the worst of climate change – a good first goal.

Getting back down to 350 ppm [CO2] in the atmosphere means removing just ~11% of the CO2 currently up there. Again using our easy metric from above, that’s about 0.3 lbs of C for every sq. ft. of agricultural land.

So why am I using this metric that refers to agricultural land? Well, when one thinks of ag land, the first thing that comes to mind is soilSoil comes in many varieties, which mainly differ by their relative composition of sand, silt, and clay, soil’s three primary components. In addition, however, soil contains organic matter. Organic matter is the decomposing matter that was once part of a plant or animal, and it’s about 58% carbon. The amount of organic matter in soil typically ranges from about 1-10%, depending on the type of soil and its health. Prairie soils before the plow came through were on the higher end of this range…conventional ag soils today are on the lower end of this range.

SO, even though the typical agricultural soil today only contains about 1-3% carbon, this number is not fixed – we can change it. In the typical agricultural “loam” soil, raising soil organic matter (SOM) by just 1% in a cubic foot of soil locks up ~0.5 lbs of C. See where I’m going with this??

THEREFORE, all we need to do to bring us back to manageable a CO2 level (350 ppm) and prevent the worst of climate change is to increase the soil organic matter in the top foot of the world’s agricultural land by just 0.62%! Since conventional agricultural practices have managed to bring down SOM by at least 1% on most agricultural land in the last 100 years, bringing it back up by just 0.62% should be EASY! How? An agricultural system that uses perennial polycultures in nature’s image to produce food, fuel, and fiber while simultaneously restoring ecosystem services and sequestering carbon. Simple.

Want to mitigate climate change? We need to get carbon back in the soil!


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