To stop the carbon in the atmosphere from increasing, we only need to grow the biomass in the soil by a hundredth of an inch per year. Good topsoil contains about ten percent biomass ... so a hundredth of an inch of biomass growth means about a tenth of an inch of topsoil. Changes in farming practices such as no-till farming, avoiding the use of the plow, cause biomass to grow at least as fast as this. If we plant crops without plowing the soil, more of the biomass goes into roots which stay in the soil, and less returns to the atmosphere. If we use genetic engineering to put more biomass into roots, we can probably achieve much more rapid growth of topsoil. I conclude from this calculation that the problem of carbon dioxide in the atmosphere is a problem of land management, not a problem of meteorology.It sounds plausible to me. The point, though, is that we need to supply incentives to people who prevent climate change without prejudging how they do so. Unfortunately Kyoto fails in this regards. It is entirely focused on reducing net anthropogenic greenhouse gas emissions. Climate Stability Bonds would be different: if Professor Dyson is right in that climate stability could be achieved by more widespread application of no-till farming methods, then a bond regime would reward research and diffusion of those methods - but Kyoto would not.
29 August 2007
Climate change and land management
Freeman Dyson writes:
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2 comments:
Yes, it sounds plausible, and since it comes from a respectable scientist (even one on "our" side in politics, if you count that he's an advocate of nuclear disarmament and international cooperation) it's all the more serious that he has chosen to speak out on an issue far away from his fields of expertise.
By all other accounts, growing or regrowing topsoil is awfully difficult. Many serious environmentalists (such as Jared Diamond in "Collapse", if I don't remember very wrong) see topsoil as so difficult to replenish that it for all practical purposes is a nonrenewable resource.
Yes, no-till agriculture reduces erosion, and that is a very good thing, but it does not replenish topsoil. No matter how kind your agricultural practices, you have to put back the nutrients you take out somehow, through some forms of fertilizer or nitrogen-binding crops. While there are promising advances (I'm keeping an eye on the biochar/agrichar technique), agronomists have been looking for such technologies for a long time anyway, so we can't expect miracles to just turn up and save us.
In the even that they do anyway, it probably won't be insurmountable to amend Kyoto to accept topsoil as a "carbon sink" on par with forests.
Thanks as always Harald. I think it was Professor Dyson's phrase "much more rapid growth of topsoil" that led me to believe he is referring not to the creation of more soil, but to the conversion of the deeper layers of soil into topsoil. Could that be right? If so, I think Dyson's optimism could be justified.
Yes, I guess Kyoto could conceptually be modified to take into account growth of topsoil. I suppose it's only slightly less realistic than monitoring forests in a meaningful way.
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