The above 'Carbon IQ test' is an excellent way of exploring how much you know about the carbon cycle, and what that means for viable solutions to our climate challenge. Have a go at it before checking out the information below. The below diagram, by Peter Donovan of the Soil Carbon Coalition, shows the amount of carbon stored in each stage of the terrestrial carbon cycle, in which carbon moves from the atmosphere, to vegetation via photosynthesis in the form of complex carbon compounds (plain 'C' in the animation), to litter and soil when the plants or leaves die, and back to the atmosphere as carbon dioxide via decay, oxidation, or burning. The facts that soil is by far the biggest carbon reservoir over which we have any direct control, and that it has proved possible to double the carbon content of soils in a decade, are why I believe that agriculture and land use may be the key frontier if we are to maintain a hospitable climate. (Figures taken from Sequestration of atmospheric CO2 in global carbon pools, Energy and Environmental Science, 1:86-100 (2008). Also note that there is about 15 times more CO2 in the oceans than in the land biosphere and atmosphere combined) In earlier posts I have looked into the climate science and shown that it is now not only necessary to reduce emissions of CO2, but to actually draw down CO2 from our atmosphere and reduce the amount that is already up there. Soil carbon can truly claim, without a hint of greenwash, to be one of nature's own solutions. The Woods Hole Research Centre has found that around 25% of carbon build-up in the atmosphere over the past 150 years has come from land use change, mainly deforestation and farming. Ohio University and others put the figure at around 50%. Organic farming techniques like avoiding nitrogen fertiliser and building up the soil's carbon content can slow this trend. But where it gets really exciting is when we realise that design systems like permaculture and keyline mean that this trend can be reversed, sucking carbon out of our atmosphere while also improving the quality of our soils to enhance food and water security, flood resilience and local community self-sufficiency. I have always been a little sceptical of 'win-win' solutions, but when they simply emerge from ending our present 'lose-lose' processes, I'm a big fan. At a European Commission conference in June last year Prof. Rattan Lal of Ohio University presented findings that, with changes to agriculture and land use, terrestrial ecosystems could naturally reabsorb sufficient CO2 to reduce atmospheric concentrations by at least 50ppm from current levels (thus taking us back under the campaigners' favourite, 350ppm). There is not yet an abundance of research in this area, but it is a tantalising possibility, and if there is one resource I recommend casting your eyes over, it's this slideshow, produced by the Soil Carbon Coalition. Edit (08/01/10) - I was sent a link to the below video by the LifeWorks Foundation. More similar videos can be seen here.