By Savanna Henderson, Humanitas Global
Agriculture is inherently vulnerable to the impacts of climate change, which threatens current and future global food and nutrition security. Agriculture accounts one one-fifth of total emissions but it also holds immense potential for adaptation and mitigation to climate change while delivering sustainable food systems. At the 2015 Paris Agreement, 94 percent of all countries included agriculture in mitigation and/or adaptation contributions. One primary reason for the recognition of agriculture in climate change action can be attributed to soils role as one of the major carbon pools (following the lithosphere and oceans). This is also one of the primary aspects of the carbon cycle that can be controlled by human activity. The recently released 2016 State of Food and Agriculture Climate Change, Agriculture and Food Security Report enthusiastically recounts the role of soil: “Soils are pivotal in regulating emissions of CO2 and other greenhouse gases. Appropriate land use and soil management lead to improved soil quality and fertility and can help mitigate the rise of atmospheric CO2”.
Carbon farming and soil-friendly farming practices have become the calling card for climate change adaptation and mitigation for a simple reason: healthy, productive soils require carbon while a stable climate requires less carbon. Some of these practices have been well-known for some time but have not been adopted at the necessary scale, or have been discouraged by incentives and input subsidies that perpetuate unsustainable practices. No-till is one such practice.
Plowing has been practiced since 8000 BC to aerate the soil and disrupt the growth of weeds that would compete with the crop through burying crop residue and disrupting growth. Technologic advances in plow design led to agricultural expansion throughout the world, converting large tracts of land into cropland. Despite the penalties witnessed during the Dust Bowl, global food production with tillage has continued to grow, reducing the prevalence of natural habitats by more than 50 percent while continuously disrupting the soil. In addition to transforming natural habitats into agriculture and releasing carbon into the atmosphere, tilling reduces the integrity and stability of the soil, increases the risk of erosion, run-off and degradation while allowing carbon to oxidize back into the atmosphere.
The concept of no-till agriculture resonates around minimizing soil disruption through obviating plowing of fields. Every year, roughly 60 gigatons of carbon enters the soil organic carbon sink as decomposing plant matter. Nearly 61 to 62 gigatons of carbon are lost from this pool as soil organic matter is oxidized by the atmosphere through tillage and erosion. Instead of plowing, farmers leave crop residue on fields after the harvest where it acts as a mulch to protect soil from erosion and a source of organic matter. This mulch reduces evaporation, which promotes water conservation and can be extremely useful in arid areas where water availability is limited. Crop residue furthermore provides soil organisms a source of food resulting in increased diversity of soil flora and fauna. Organisms like worms create channels in the soil that foster root growth and alongside the lack of tilling, contribute to a more stable internal structure that is resilient to environmental stressors and improves capacity for growth.
Despite all the benefits associated with no-till, adoption has been low for a number of reasons:
- The specialized seeders needed can be prohibitively expensive.
- In developing countries, crop residues are often already utilized as fuel and animal feed, leaving nothing to mulch the crop with.
- Different pest species can arise during a shift from tilled cropland to no-till requiring further adaptation and planning.
- Some no-till crops require a heavier reliance on herbicides and fungicides as the increased moisture promotes increased growth.
- Expected changes from tilled to no-till can sometimes take years or decades to reveal themselves depending on the soil, region and other biophysical attributes. During this time productivity and yields could be reduced decreasing the calories and income available to the farmer.
- There are also questions around the rates of soil organic carbon sequestration that have been researched and published for the past 20 years.
Under the right conditions, no-till is a climate-smart agricultural technique that supports food and nutrition security while providing resilience to climate change. Such a practice deserves more attention as leaders at the 22nd Session of the Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) focus on action needed to achieve priorities set out in the Paris Agreement. Countries with agriculture included in adaptation and/or mitigation contributions must develop action plans with clear objectives to achieve climate targets. Beyond COP22, there needs to be a refocus on sustainable and climate-smart agricultural practices that can be scaled and adequately supported by policy and investments.
It remains clear that soil management is key to agricultural adaptation and mitigation. In a companion post, I will look more closely at additional agricultural practices that support soil carbon sequestration.
