SPEAKER: 2015 is the year of the soil, and in December we have the World Soil Day coming up. And that's very exciting, because we have now something to hold onto. We have a body, a UN body that champions soils. Before, soils were neglected. There were no UN resolutions on soil, but now we have a champion that promotes the stewardship and the sustainable use of soils.
And as as part of the celebration on soils, we have put together a special issue in the magazine "Nature," and as part of that special issue, we make an important point about soil organic matter. Soil organic matter makes up more carbon than the vegetation and the atmosphere combined, so small changes in soil carbon contents have a huge impact on the climate.
So we need to be able to predict the behavior of soil carbon in a warming world, and that's only possible if we have the right kind of model, and can mathematically predict what is happening in 50 or 100 years from now. But we have built this model with a wrong understanding that plant material is broken down, and then re-combined to large humic substances.
This understanding could not be confirmed by a modern analytical tools. The last 10 years have clearly shown that humic substances, large, complex molecules are not formed in soil. So any model that builds on that notion of large humic substances is not able to predict the behavior of carbon in a warming world. That's why that this very important to revise our understanding of what soil organic matter is actually composed of.
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Johannes Lehmann, professor of soil science, discusses the United Nation’s World Soil Day. Further, he talks about a special section of the journal Nature, which celebrates soil.