Terrestrial carbon sequestration is the best way to buy time in a warming world. Cutting emissions will help, but not as immediately as sequestration. Making sequestration a priority matters, given critical policy choices that must be made as evidence of current, specific climate-change impacts to agriculture and wildlife mounts.
The Rodale Instituteâ€™s vigorous call for land-based biological sequestration dovetails with contentions found in a recently published Worldwatch Institute report on climate change: 2009 State of the World: Into a Warming World. A chapter entitled â€œFarming and Land Use to Cool the Planetâ€ by Sara J. Scherr and Sajal Sthapit examines ways to reverse the trend of environmentally destructive agriculture and use carbon sequestration to mitigate climate change.
They argue that food production must be fundamentally restructured to simultaneously preempt and react to the devastating effects of climate change. They confirm the Rodale Instituteâ€™s contention that reexamining the role of carbon in agriculture is a vital first step in this restructuring process.
The Institute posits that organic agriculture presents an untapped solution, an underutilized carbon sink at the ready. A conservative extrapolation of carbon sequestration data drawn from our own long-term research indicates that, if the worldâ€™s 3.5 billion tillable acres could be transitioned to organic agriculture now, land could sequester almost 40 percent of our current carbon emissions. No other proposed carbon mitigation solution comes close to that potential impact, particularly using existing and readily available technology.
The Worldwatch authors argue that a food-centric approach might catalyze a climate-saving revolution. "A worldwide, networked movement for climate-friendly food, forest, and other land-based production is needed. This calls for forging unusual political coalitions that link consumers, producers, industry, investors, environmentalists, and communicators. Food, in particular, is something that the public understands." (p 49)
Scherr and Sthapit illustrate the interconnection of carbon and other current environmental issues: "Land uses and management systems that are accelerating greenhouse gas emissions (GHG) are also undermining the ecosystem services upon which long-term food and fiber production dependâ€”healthy watersheds, pollination, and soil fertility."
They recommend multiple strategies for carbon sequestration, including organic farming, reduced tillage, use of biochar to aid in revegetation of degraded soils, retaining forests and grasslands as carbon sinks, agroforestry and perennial cropping to retain more biomass, rotational grazing, and biogas digestion to convert manure into energy and organic fertilizer. They include several good suggestions in ramping up the quest for better perennials, such as looking at more tree crops for food production and finding suitable perennial biodiesel crops.
The authors cite the Instituteâ€™s research documenting soil organic matter increases of 15 to 28 percent over a 22-year period, but say more research is needed â€œto understand the potentials and limitations of biologically based soil nutrient management systems across the range of soil types and climatic conditions.â€ (p. 35)
The chapter also recognizes the importance of geographical context when considering these improvements: â€œThe actual net impacts on greenhouse gases of reduced emissions and increased carbon storage from reduced tillage depend significantly on associated practices, such as the level of vegetative soil cover and the impact of tillage on crop root development, which depends on the specific soils type.â€ (p. 36) Carbon material binds more easily to clay or loamy soil particles than to sand, making already good quality soil readily improvable.
We welcome more organic research in more places, incorporating timeless farmer wisdom with advanced science to adapt organic principles to local conditions. Letâ€™s also:
Rethink the value of soil carbon, elevating it to the position it deserves. This means reprioritizing our land use patterns, moving preservation of prime farmland to a high priority for national ecological security.
Focus on building biologically active soil organic matter that leads, by default, to more sustainable and environmentally sound agriculture.
Credit the added benefits of fertilizer reduction and water management. Since organic systems can use compost, manure and cover crops for fertility, they gradually eliminate the need for chemical fertilizers due to increases in naturally cycling fertility. At the same time, the soil water-holding capacity improves to better maintain crop growth and production in drier and wetter years. Keeping diverse and nearly year-round vegetative cover growing on the soil surface has the benefit of holding soil in the field (rather than losing it to erosion) and improving rainwater infiltration through the soil profile to recharge groundwater.
Recognize that even annual crop systems can transition away from greenhouse gas emission to carbon sequestration in the form of carbon compounds.
The Instituteâ€™s 29-year-long Farming Systems Trial (FST) has shown that, after the initial transition phase, organic annual systems produce a competitive yield and often do better than conventional systems in drought years. This may be due to a relatively high rate of moisture-absorbent carbon content in organic rotations, as Institute trials also show accumulation of 500 lb/C/a/yr (legume) to 2,000 lb/C/a/yr (compost) in various long-term observations.
Scherr and Sthapit target these agricultural solutions:
"In terms of climate change, landscape and farming systems should actively absorb and store carbon in vegetation and soils, reduce emissions of methane from rice production, livestock, and burning, and reduce nitrous oxide emissions from inorganic fertilizers. At the same time, it is important to increase the resilience of production systems and ecosystem services to climate change." (p 33)
The Instituteâ€™s work shows that organic practices have the power to work toward these solutions. We know, for example, that mycorrhizal fungiâ€”microorganisms that work in symbiosis with plant roots and help supply them with nutrientsâ€”are more prevalent in the carbon-rich soils of organically managed systems. Mycorrhizae secrete glomalin, a glue-like substance, that actually conserves organic matter by aggregating it with clay and mineral soil particles. While mycorrhizae have been the focus of our research on soil microbial life over the past few decades (conducted in conjunction with USDA researcher David Douds), they are part of a vast community of organisms found just below the soil surface that deliver diverse but comparable benefits to the crop ecosystem when soil is managed for health and biodiversity.
Minimal tillage, advocated in the report, has many benefits as well, and is most effective when used in concert with a diverse rotation. Reducing tillage also presents an effective way to cycle nutrients and store carbon. As Scherr and Sthapit point out, tillage can disrupt critical microbial functions by exposing anaerobic microbes to oxygen and suffocating aerobic microbes by working them deeper into the soil. Minimal tillage encourages a more biologically rich soil environment than does no-till, with less carbon loss than conventional tillage.
The authors suggest, finally, the use of the FAO Global Carbon Gap Map which helps identify areas where soil carbon storage is greatest and targets geographic regions where it is lacking. This map could pin-point the most promising regions to start using organic methods to restore degraded land.
The individual practices recommended by the authors are already used in various locations throughout the world. These carbon-building techniques, when they are coordinated into a dynamic system, constitute what the Rodale Institute calls regenerative organic agriculture. Scientific examination and practical application of each individual component is vital to understand their roles in a complete organic system. With this understanding, we can then work effectively with farmers to implement as many practices as quickly as possible to affect real carbon sequestration benefits.
Research and outreach provide the practice guidelines that allow food producers to make meaningful changes to their field and rangeland management. Policy makers and consumers are critical, however, in providing the economic support that allows farmers to transform agriculture into a climate-saving force around the world.
Source: Rodale Institute and OCA
See Scherr and Sthapitâ€™s chapter, â€œFarming and Land Use to Cool the Planetâ€