Forest soils contain more humus than grassland soils, and these in turn contain more humus than cropped arable soils. The continuous tilling and ploughing of soils activates soil bacteria, fungi, and soil fauna which break down humus. This process generates CO2, which as a greenhouse gas ultimately contributes to global warming.
Current international agreements have been supporting afforestation as a measure to combat the loss of humus. Soils low in humus – products of industrialized farming – can thus be returned to a state where humus formation prevails, a process which removes CO2 from the atmosphere. For plants, carbon dioxide from the air is their main ‘building material’ and in natural ecosystems their roots, leaves and shoots eventually form humus. Millions of years ago, humus and remains of plants and animals subjected to high pressure over geological time turned into crude oil and coal which we are so recklessly burning today.
In Copenhagen, farmers and their organisations are fighting to present agriculture in a new light – as being climate-friendly. The key aspects are to work more carefully with soil fertility, to encourage humus formation, to produce biomass and biodiesel, and to use more efficient cultivation techniques in order to avoid the release of unnecessary amounts of greenhouse gases.
Agriculture has a huge potential to slow global warming. Even just a moderate rate of humus formation could elegantly fix between 5 and 15 gigatonnes of CO2 annually, thus reducing total anthropogenic GHG emissions by between 10 and 30%. And the potential is even bigger than that. Many agricultural soils contain only a fraction of the amount of organic matter they would have contained prior to the industrial revolution. So why shouldn’t we use this natural potential for carbon storage as long as our society continues to be dependent on burning fossil fuels?
The farmers at COP 15 agree. Alexander Müller, Assistant Director-General of the FAO in Rome, has called for agriculture to be included in the negotiations not merely as a cause of climate change but also as an integral part of the ultimate package of climate change solutions. During the first week of negotiations a tough struggle was fought on this issue and it appears the FAO has been successful. Whether the farming sector will in future receive support for its efforts in combating climate change will only be decided in the second week of negotiations, but for once the group of 131 developing countries (G-77) and the major agricultural exporting countries (CAIRNS) are moving in the same direction.
However, if agriculture becomes part of the mitigation strategy the fight is only just beginning. Which type of agriculture is really suited to sustainably mitigate climate change? How divergent expert opinion is on this matter became evident during the first days of the conference. Many parallel discussions wrestled with the question of which strategy was the most convincing. After all, there is a lot of money at stake. Here are some impressions:
Supported by industry groups, non-organic farmers praised “no-till farming”. While this method prevents soil erosion and increases soil humus content, there are many drawbacks. The plough is replaced with non-selective herbicides in order to clear weeds from the fields. Genetically modified maize and soybean cultivars are planted which can withstand the non-selective herbicides. Moreover, no-till generally involves increased use of energy-consuming chemical fertilizers and the soils are less well aerated which increases the amounts of the other two GHGs, methane and nitrous oxide, they release.
But old ideas are also presented in new packaging. Experts unabashedly advocate the increased use of fertilizers and pesticides in order to boost harvests. The more biomass is produced on arable land the better for the climate, they say. But they ignore that fact that intensive agriculture has already contributed significantly to the degradation of ecosystems and the environment and that it makes very inefficient use of energy and fertilizers. For example, the rate at which nitrate fertilizer, which is produced from fossil fuels, is actually taken up by plants to form biomass is now as low as 17%. The remainder pollutes our soils, watercourses, and the air.
In contrast, the proposals forwarded by experts on the biochar method appear more interesting. The model for this type of carbon sequestration is derived from the fertile Terra Preta soils the Amazon Indians created 500 to 800 years ago. These indigenous peoples charred the wood derived from clearing parts of the rainforest to create fields by carbonizing it at high temperature in the absence of oxygen, and this charcoal was then incorporated into the soil of the new fields. Charcoal prepared in this way has led to sustainable humus formation and this humus is stable, even in tropical soils where organic matter such as compost is quite rapidly broken down and disappears.
Can biochar technology be transposed to modern agriculture in that harvest residues, straw, compost material, wood, shrubs, or even paper are charred and incorporated into soils? Johannes Lehmann, the world’s leading researcher on this topic at the US-American Cornell University, is aware that the knowledge gaps on biochar systems are as yet too significant to recommend this method for practical application. Nevertheless, some companies have commenced production of small and large pyrolysis units. The smallest units are stoves costing less than $ 10 which generate heat for cooking and produce biochar as a by-product.
The International Federation of Organic Agriculture Movements (IFOAM) is the only organization to call for radical rethinking in the farming sector. According to IFOAM, arable and livestock production should once again be harmonized in natural cycles, soil fertility and fertilizers should solely be based on organic substances (livestock manure, compost, green manure, and clover), energy-intensive chemical fertilizers produced from fossil fuels have no place in sustainable agriculture, and chemical pesticides reduce biodiversity and impact on the environment.
Two weeks before the Copenhagen summit, scientists of the CarboEurop European research team published worrying new data on intensive farming and livestock production. According to Detlef Schulze of the Biogeochemistry Department of the Max Planck Institute in Jena, Germany, who was the leader of the study, GHG emissions from intensive farming and livestock production exceed carbon sequestration by forests and grasslands. In Copenhagen, agriculture now has the unique opportunity to distance itself from this negative image. But this requires courageous steps forward onto a path of resolutely sustainable farming. Organic farming will be a driving force on this path.
Urs Niggli, December 13, 2009
- cop15.dk: Homepage of the Climate Change Conference in Copenhagen
- carboeurope.org: Homepage CarboEurope IP
- mpg.de: Jena ax-Planck-Institut
- FAO.org: FAO-pages on the UN Climate Change Conference
- IFOAM.org: IFOAM pages on the UN Climate Change Conference