Climate Change and Carbon Ranching
By Courtney White, Quivira Coalition
Reprinted thanks to Courtney White and the Quivira Coalition. To read the full article, visit www.quiviracoalition.org.
Novelist and historian Wallace Stegner once said that every book should try to answer an anguished question. In the case of climate change, an anguished question is this: what can we do right now to help reduce atmospheric carbon dioxide (CO2) from its current (and future) dangerously high levels?
In an editorial published in July of 2009, Dr. James Hansen of NASA proposed an answer: “cut off the largest source of emissions – coal – and allow CO2 to drop back down… through agricultural and forestry practices that increase carbon storage in trees and soil.” Personally, I’m not sure how we accomplish the coal side of the equation, which requires governmental action, but I have an idea about how to increase carbon storage in soils.
I call it a carbon ranch.
The purpose of a carbon ranch is to mitigate climate change by sequestering CO2 in plants and soils, reducing greenhouse gas emissions, and producing co-benefits that build ecological and economic resilience in local landscapes. “Sequester” means to withdraw for safekeeping, to place in seclusion, into custody, or to hold in solution – all of which are good definitions for the process of sequestering CO2 in plants and soils via photosynthesis and sound stewardship.
The process by which atmospheric CO2 gets converted into soil carbon is neither new nor mysterious. It has been going on for millions and millions of years and all it requires is sunlight, green plants, water, nutrients, and soil microbes. According to Dr. Christine Jones, a pioneering Australian soil scientist, there are four basic steps to the CO2 / soil carbon process:
Photosynthesis: This is the process by which energy in sunlight is transformed into biochemical energy, in the form of a simple sugar called glucose, via green plants – which use CO2 from the air and water from the soil, releasing oxygen as a byproduct.
Resynthesis: Through a complex sequence of chemical reactions, glucose is resynthesized into a wide variety of carbon compounds, including carbohydrates (such as cellulose and starch), proteins, organic acids, waxes, and oils (including hydrocarbons) – all of which serve as fuel for life on Earth.
Exudation: Around 30-40% of the carbon created by photosynthesis can be exuded directly into soil to nurture the microbes that grow plants and build healthy soil. This process is essential to the creation of topsoil from the lifeless mineral soil produced by the weathering of rocks over time. The amount of increase in organic carbon is governed by the volume of plant roots per unit of soil and their rate of growth. More active green leaves mean more roots, which mean more carbon exuded.
Humification: or the creation of humus – a chemically stable type of organic matter composed of large, complex molecules made up of carbon, nitrogen, and minerals. Visually, humus is the dark, rich layer of topsoil that people associate with rich gardens, productive farmland, stable wetlands, and healthy rangelands. Land management practices that promote the ecological health of the soil are key to the creation and maintenance of humus. Once carbon is sequestered as humus it has a high resistance to decomposition, and therefore can remain intact and stable for hundreds or thousands of years.
Additionally, high humus content in soil improves water infiltration and storage, due to its sponge-like quality and high water-retaining capacity. Recent research demonstrates that one part humus can retain as much as four parts water. This has positive consequences for the recharge of aquifers and base flows to rivers and streams, especially important in times of drought.
In sum, the natural process of converting sunlight into humus is an organic way to pull CO2 out of the atmosphere and sequester it in soil for long periods of time. Any land management activity that encourages this equation, can help fight climate change. There are at least six strategies to increase or maintain soil health and thus its carbon content.
Three sequestration strategies include:
(1) Planned grazing systems. The carbon content of soil can be increased by the establishment of green plants on previously bare ground, deepening the roots of existing healthy plants, and the general improvement of nutrient, mineral, and water cycles in a given area. Planned grazing is key to all three. By controlling the timing, intensity, and frequency of animal impact on the land, a ‘carbon rancher’ can improve plant density, diversity, and vigor.
Specific actions include: the soil cap-breaking action of herbivore hooves, which promotes seed-to-soil contact and water infiltration; the ‘herd’ effect of concentrated animals, which can provide a positive form of perturbation to a landscape by turning dead plant matter back into the soil; the stimulative effect of grazing on plants, followed by a long interval of rest (often a year), which causes roots to expand while removing old forage; targeted grazing of noxious and invasive plants which promotes native species diversity; and the targeted application of animal waste, which provides important nutrients to plants and soil microbes.
(2) Active restoration of riparian, riverine, and wetland areas. Many arroyos, creeks, rivers, and wetlands in the U.S. exist in a degraded condition, the result of historical overuse by humans, livestock, and industry. The restoration of these areas to health, especially efforts that contribute to soil retention and formation, such as the reestablishment of humus-rich wetlands, will result in additional storage of atmospheric CO2 in soils. There are many co-benefits of restoring their health, including improved habitat for wildlife, increased forage for herbivores, improved water quality and quantity for downstream users, and a reduction in erosion and sediment transport.
(3) Removal of woody vegetation. Many meadows, valleys, and rangelands have witnessed a dramatic invasion of woody species, such as pinon and juniper trees over the past century, mostly as a consequence of the suppression of natural fire and overgrazing by livestock (which removes the grass needed to carry a fire). The elimination of over-abundant trees by agencies and landowners has been an increasing focus of restoration work recently. One goal of this work is to encourage grass species to grow in place of trees, thus improving the carbon-storing capacity of the soil. The removal of trees also has an important co-benefit: they are a potential source of local biomass energy production, which can help reduce a ranch’s carbon footprint.
Three maintenance strategies that help keep stored CO2 in soils include:
(4) The conservation of open space. The loss of forest, range, or agricultural land to subdivision or other types of development can dramatically reduce or eliminate the land’s ability to pull CO2 out of the atmosphere via green plants. Fortunately, there are multiple strategies that conserve open space, including public parks, private purchase, conservation easements, tax incentives, zoning, and economic diversification that helps to keep a farm or ranch in operation. Perhaps most importantly, the protection of the planet’s forests and peatlands from destruction is crucial to an overall climate change mitigation effort.
(5) The implementation of no-till farming practices. Plowing exposes stored soil carbon to the elements, including the erosive power of wind and rain, which can quickly cause it dissipate back into the atmosphere as CO2. No-till farming practices, especially organic ones (no pesticides or herbicides), not only protect soil carbon and reduce erosion, they often improve soil structure by promoting the creation of humus. Additionally, farming practices that leave plants in the ground year-round both protect stored soil carbon and promote increased storage via photosynthesis. An important co-benefit of organic no-till practices is the production of healthy food.
(6) Building long-term resilience. Nature, like society, doesn’t stand still for long. Things change constantly, sometimes slowly, sometimes in a rush. Some changes are significant, such as a major forest fire or a prolonged drought, and can result in ecological threshold-crossing events, with deleterious consequences. “Resilience” refers to the capacity of land, or people, to ‘bend’ with these changes without ‘breaking.’ Managing land for long-term carbon sequestration in soils requires building resilience as well, including the economic resilience of the landowners, managers, and community members.
All of these strategies have been field-tested by practitioners, landowners, agencies and researchers and demonstrated to be effective in a wide variety of landscapes. The job now is to integrate them holistically into a ‘climate-friendly’ landscape that sequesters increasing amounts of CO2 each year.
Look for Part 2 of Courtney White’s essay “Carbon Ranching” in the April issue of the Co-op Connection News, or visit www.quiviracoalition.org to read the full essay.