Soil Carbon and Climate Change
Getting to the Root Cause of - and the Solution - to Global Warming
by Thomas J. Elpel
If we could flip a switch tomorrow and instantly end our dependency on fossil fuels, would we halt global warming and stabilize the climate? The answer, unfortunately, is no. Excessive reliance on fossil fuels is neither the sole cause nor the biggest player in global climate change, as popularly believed. The bigger issue - and the solution - to global warming, lies right underneath our feet.
What gives healthy soil that rich brown or black color? Carbon. Specifically, it is carbon extracted by plants from the atmosphere. Without the aid of humanity, nature itself transformed the sterile mineral substrate into fertile, carbon-rich soil. Plants breathe in carbon dioxide from the atmosphere, convert the carbon into vegetative matter, and exhale oxygen back into the atmosphere. Over time, dead vegetation decomposes to help build rich brown or black soil. Worldwide, soils contain at least 1,500 gigatons of carbon, compared to 750 gigatons held in the atmosphere and 650 gigatons held in plant matter like the tropical forests. (A gigaton is a billion tons.)i
Unfortunately, we are rapidly losing our soil carbon to the atmosphere. As stated by the Soil Science Society of America, "Many cropland soils of the United States have lost as much as 50% of their original SOC (soil organic carbon) due to the effects of land clearing and tillage. Such conventional farming practices "burn" SOC just as we burn fossil fuels today."ii Human activity and ignorance have degraded once-fertile soils, fostering desertification and allowing gigatons of soil carbon to escape back into the atmosphere. While there is much talk about reducing soil loss in agriculture, there is rarely any discussion of building new soil.
The damage has been ongoing for millennia, accelerating exponentially in recent times along the same curve as the growth in global population and agriculture. In China, for example, human-caused desertification was first documented in the fourth century B.C. and has spread ever since. Desertification accelerated over the last hundred years due to a combination of deforestation, grazing mismanagement, and over-cultivation. Twenty-seven percent of China is now covered by useless sand, which threatens to bury the capital of Beijing under advancing dunes.iii In other words, 27 percent of the country has effectively lost 100 percent of its soil carbon, and sand is all that is left.
Carbon is fairly stable in protected soils. Exposing soil to oxygen, due to plowing, lack of vegetative cover, and erosion, allows microbes to consume the organic matter as food, exhaling carbon dioxide gas back into the atmosphere.iv The less protected the soil is, the more it is prone to erosion, desertification, and oxidation by microbes. The bottom line is that desertification drives climate change.
Desertification is caused by numerous factors, including natural climate variation, excessive use of fire, poor livestock management, and farming. Australian Aborigines used fire extensively 50,000 years ago to hunt big game animals, hunting many species to extinction, while contributing to desertification of the continent.v After settlement in 1788, European-style farming and ranching accelerated desertification. More than 70 percent of Australian farmland has been seriously degraded, losing an estimated 50 to 80 percent of the carbon formerly locked up in topsoil.vi
Similarly, 10,000 years ago, much of the Middle East supported forests and grasslands, which turned to desert due to deforestation, agriculture, and poor grazing practices. Likewise, the rich soils of the Sahara once grew the grain that supported the Roman Empire. But now the soil is gone, oxidized back into the atmosphere or blown out to sea, leaving barren sand and rock covering an area nearly as large as the United States.
Counterintuitively, grasslands and croplands are far bigger players in carbon sequestration than forests. Forests contain significant quantities of organic carbon, but trees often grow very slowly, and most of the carbon is typically stored in the wood, rather than in the soil. An acre of grass, on the other hand, can absorb more carbon per year than an acre of forest, and much of that organic carbon can decompose to enrich the soil under favorable conditions. More than half of the earth's land surface consists of grasslands. If we can reverse the trend, and learn from nature how to build soil from air, then we can extract carbon from the atmosphere and begin to reverse global warming. But first, we must understand the problem.
Many farmers, ranchers, scientists, governments, and even environmental organizations advocate grassland fires. Worldwide, billions of acres are torched every year. By conventional wisdom, these grass fires are considered necessary for rangeland health. Fire removes old, dead plant matter, allowing sunlight to reach new growth at the base of the plants. Hypocritically, climatologists warn us that burning tropical forests contributes to global warming, while condoning or excusing the significantly greater carbon emissions from grass fires. The amount of carbon released in these grassland fires is difficult to fathom.
For comparison, the London-based department store chain, Marks and Spencer, decided to spend £200 million (US$ 400 million) on a five-year plan to make the company carbon neutral. Their investment was estimated to achieve a savings equivalent to keeping 100,000 cars off the road. While this is an admirable effort, the avoided emissions are approximately the equivalent of preventing just one fifteen-acre grass fire in Kansas or Kenya each year.vii
It is commonly argued that grassland fires are "carbon neutral," because the carbon originated in the atmosphere and was extracted by living plants and trees. Burning the vegetation merely returns the carbon to the atmosphere where plants will extract it again, so it isn't considered a net increase in atmospheric carbon. On the other hand, carbon lost to the atmosphere cannot become part of the soil either, halting carbon sequestration and soil formation.
While there are always natural fires that inhibit carbon sequestration, the frequency and scope of man-made fires dwarfs naturally occurring fires. Biomass fires, most of them on grasslands, presently account for about 40 percent of global annual carbon dioxide emissions.viii In addition to halting the process of soil formation, fire destroys organic litter that is essential to protect soil from erosion. Moreover, the exposed soil is prone to oxidation. The more that the soil is exposed, through plowing or wind-blown erosion, the greater the carbon loss to the atmosphere.
Organic litter is essential to provide protection for young seedlings in seasonal rainfall environments. Without protective cover, new grasses and forbs are unable to establish themselves to replace dying old growth. This leads to more bare ground, more erosion, and more oxidation of the soil carbon.
The only reason these grassland fires seem "necessary" is due to human-caused changes in the natural grazing sequence.
Learning from Nature
Here in America, our western rangelands were historically grazed and maintained by massive herds of buffalo. The important part was not the buffalo, but the sequence of grazing. Before the arrival of Europeans, predators forced the buffalo to stay clustered in tight herds for safety. Some herds were so massive that observers described them as miles wide and hours or days long in passing. They crushed everything in their path, trampling the grasses and sage - every bit of organic matter, into the soil. Their hooves and urine killed the moss, while plant seeds were pounded into the soil. Old or dead vegetation was trampled into the ground where microbes could break it down. The organic debris helped retain moisture for plant growth. Gradually the debris rotted and returned nutrients to the soil. The migrating bison allowed the prairie to recover without further interference, enabling lush and unrestrained growth. Over time, the bison helped build the fertile prairie soils.
Allan Savory, author of Holistic Management, first realized the predator-prey connection while working as a young biologist and game ranger in Africa in the 1950s, as described in his essay, "A Global Strategy for Addressing Climate Change."
Studying the damage experienced through government policy to burn Africa's grasslands I could not help but observe that the healthiest land was associated with remnant wild populations of large game animals. Where large populations of thousands of buffalo and other game, complete with packs of lions that followed closely and kept the herds bunched, the soil and vegetation was healthiest. What the wild, large concentrated herds did not consume, they trampled onto the ground, thus removing the old growth and preparing both plants and soils for new growth. The animals in intact communities were doing what we were using fire to do, but doing it better with no adverse effects of soil, wetlands, springs and rivers.
The world's vast savannas and grasslands developed over millions of years with soil, soil life, plants, grazing herbivores and their predators-all acting as one vast indivisible functioning whole in nature. The world's large grazing animals tend to run in herds as a defense strategy against pack-hunting predators. The larger the number of animals, both prey and predator, the larger the herd masses. Such herding grazers have what are referred to as non-self-regulating populations. This means their numbers are only controlled by accident, disease or predation, rather than any innate breeding control. Because they cannot regulate their own numbers these populations were often enormous with numbers running to many millions.
The diaries of early travelers in Africa and the Americas record vast herds, which in all likelihood were but remnants of earlier much larger numbers. In the early 1800s, for instance, some 17,000 antelope were shot in a one-day hunt provided for the Prince of Wales in South Africa. Records kept by early South African pioneers describe substantial wetlands, sponges and springs associated with the vast herds but which dried up rapidly as soon as the herds were killed off and their former role was replaced with fire.
Today with far fewer numbers still, the same land is considered desert, despite no change in rainfall. The evidence appears strong that large numbers were the rule rather than the exception in the grasslands humans inherited. And yet to save these grasslands today, the common prescription is to reduce or remove the animals, especially livestock, so the grasses and soils can "recover" and then to burn the old material to keep the plants alive.ix
In seasonal rainfall environments, fencing and stocking the land creates a new sequence of grazing, which logically has a different effect on the ecology. Without predators, cattle spread out and graze over wide areas; they no longer trample standing dead grasses from previous years. The dead grass blocks incoming sunlight, killing new growth below. Old vegetation stands for years, turning grey as it slowly breaks down through chemical oxidation and weathering. Valuable nutrients in the old growth are unavailable to living plants. In fenced pastures, livestock eat tender new growth before the vegetation can recover. Burning the range accelerates desertification by stealing the organic matter that protects the soil and new seedlings from drying out.
Loss of organic matter also results in poor soil structure. Raindrops strike the exposed soil, pulverizing and separating loose, aggregated clumps. The fine particles of silt, sand, and clay solidify as a hard surface crust. Seeds and water cannot penetrate the capped surface, so bare patches develop between the plants. Weeds, brush, and grasshoppers thrive in the open patches. New moisture is lost as runoff and contributes to flooding. Water bypasses the water table and old springs dry up.
In South Africa, Dutch settlers established communities around free-flowing springs they called "fonteins." They named their towns after the springs and the abundant wildlife: Elandsfontein, Springfontein, Buffelfontein. Settlers described herds of springbok (like antelope) so vast that they trampled everything in their path as they migrated through, including teams of oxen that could not be unhitched in time. Now the grasslands, the springs, and the wildlife are gone, and the remaining range supports very few livestock. The climate did not change according to weather records, but the land still turned to desert.x
Similarly, the official USDA stocking rate for cattle in West Texas a hundred years ago would seem utterly unbelievable today. Drive through West Texas and you will likely see less than 100 head of cattle in 300 miles. What you will see is mile after mile of dying grasslands, with about 80 percent of the soil surface consisting of bare ground.xi
Seedling germination in seasonal rainfall environments is always a challenge, even under the best of circumstances. Seeds must be thoroughly mixed with soil and covered with organic matter and manure fertilizer to retain moisture and protect them from the sun. Otherwise, the delicate seedlings dry out and die before they become established. The more extreme or brittle the climate, the more difficult it is for new seedlings to germinate. The Salt Lake City area was once described as having grass "belly high to a horse," yet that is not the landscape today. The landscape is grey because the grass is gone.
Halting desertification and turning these barren wastelands back into fertile, productive landscapes is relatively easy, but it requires playing by the rules of the ecosystem. In other words, it requires holistic thinking. By mimicking ecosystem processes, we can restore the health of the land and still attain a high level of productivity.
Don and Cleo Shaules, who live near Billings, Montana, embraced holistic thinking to run a sustainable ranch. They mimicked the historical sequence of grazing with the aid of carefully planned fences, putting more animals in smaller spaces for shorter periods of time. Additional impact is achieved by herding the animals, or by putting feed or supplements in areas where impact is especially desired. The cows trampled organic carbon into the soil and inoculated it with bacteria from the manure. With animal impact, the Shaules successfully trampled cactus and sagebrush into the dirt, providing essential organic cover to protect new seedlings. The rich, brown soil humus increased from 1/4 inch up to 1 1/2 inches in just ten years! (Photo courtesy of Wayne Burleson.) They built soil from air, and more than doubled their livestock numbers along the way.xii
Similarly, Colin Seis, an Australian farmer, doubled the organic carbon in his soil in little more than a decade by sowing cereal crops into his perennial pastures. In other words, he grows harvestable crops on the same land he manages for intensive grazing, which translates to increased productivity and higher profits. Thousands of other Australians are now adopting his methods. xiii
The top few inches of soil contain "active" carbon, which easily cycles back into the atmosphere. However, as soil health improves, carbon migrates deeper into the ground, building soil as it goes. This new soil formation can be "breathtakingly rapid," according to soil researcher Christine Jones. Test plots sequestered 168.5 tons of carbon dioxide per hectare over twenty years, accelerating to 33 tons per hectare per year in the final two years of monitoring. On the other side of the fence, in a conventionally managed pasture, soil formation remained stagnant.xiv
Healing the Land
Restoring planetary soil health to properly sequester carbon again requires that we either bring back or mimic the natural processes that built fertile soil from air in the first place. While it might be nice to dream of a day when wild animals and their predators will roam freely again, practical necessity requires that we employ livestock, ranchers, and land managers to address the immediate crisis. We can reverse desertification and halt climate change by increasing stock numbers and mimicking the patterns and movement of wild herds. Animal impact can replace the need for frequent burning, while enhancing the production of organic matter and maintaining soil cover. Through holistically managed planned grazing, livestock can become tools for land reclamation, while producing sustenance or profit for those managing them.
Increasing soil organic matter by an easily achievable 0.5 percent across the 4.9 billion hectares of grasslands and croplands across the planet would remove an estimated 720 gigatons of carbon dioxide from the atmosphere.xv Boost the organic content of our soils by a percent or two, and we can put global warming in retreat. Equally important, sequestering carbon in this manner reverses desertification, reduces the frequency and severity of floods and droughts, increases productivity and profits, and addresses a root cause of social instability and violence.
Healing our beleaguered planet is not so much about finding new answers, as recognizing that nature had the answers all along, and we just failed to see what was right beneath our feet.
Thomas J. Elpel is the author of Botany in a Day: The Patterns Method of Plant Identification, and numerous other books about nature, wilderness survival and sustainable living.
i _____. "The Soil Carbon Manifesto." http://www.carboncoalition.com.au/. Accessed November 6, 2007.
ii _____. "Carbon Sequestration: Position of the Soil Science Society of America." https://www.soils.org/files/about-society/carbon-sequestration-paper.pdf. Accessed March 16, 2011.
iii Ron Gluckman, Fengning, and Langtougou. "Beijing's Desert Storm." http://www.gluckman.com/ChinaDesert.html. Accessed December 18, 2007.
iv _____. "Soil Carbon." Wikipedia. http://en.wikipedia.org/wiki/Soil_carbon. Accessed March 27 2011.
v Jim Scott. "Arid Australian interior linked to landscape burning by ancient humans." http://www.eurekalert.org/pub_releases/2005-01/uoca-aai012505.php. January 25, 2005. Accessed November 6, 2007.
vi Michael Perry. "Australia's carbon farmers in quiet revolution." World Business Council for Sustainable Development. http://www.wbcsd.org/plugins/DocSearch/details.asp?txtDocTitle=Australia's%20carbon%20farmers%20in%20quiet%20revolution. Accessed April 4, 2011.
vii Allan Savory. "A Global Strategy for Addressing Climate Change." http://www.savoryinstitute.com/storage/articles/A%20Global%20Strategy%20for%20Addressing%20Climate%20Change%202%20_1_.pdf Accessed March 16, 2011.
viii Joel S. Levine et al. "Biomass Burning: A Driver for Global Change." Environmental Science & Technology. March 1995. http://asd-www.larc.nasa.gov/biomass_burn/globe_impact.html. Accessed March 27, 2011.
ix Allan Savory. "A Global Strategy for Addressing Climate Change." http://www.savoryinstitute.com/storage/articles/A%20Global%20Strategy%20for%20Addressing%20Climate%20Change%202%20_1_.pdf Accessed March 16, 2011.
x Allan Savory with Jody Butterfield. Holistic Management. Island Press: Washington, D.C. 1988, 1999. Pages 41 - 42.
xi Allan Savory. "A Global Strategy for Addressing Climate Change." http://www.savoryinstitute.com/storage/articles/A%20Global%20Strategy%20for%20Addressing%20Climate%20Change%202%20_1_.pdf Accessed March 16, 2011.
xii Wayne Burleson. "Our Fences are Shrinking." The Whole Approach. Belgrade, MT. Vol. 1, No. 1. Page 7 - 8.
xiii _____. "The other side of global warming." ManagingWholes.net. http://managingwholes.net/?p=22. Accessed October 24th, 2007.
xiv Christine Jones, PhD. "Carbon that counts." Soil Carbon Coalition. http://soilcarboncoalition.org/files/JONES-Carbon-that-counts-20Mar11.pdf. Accessed March 27, 2011.
xv Allan Savory. "A Global Strategy for Addressing Climate Change." http://www.savoryinstitute.com/storage/articles/A%20Global%20Strategy%20for%20Addressing%20Climate%20Change%202%20_1_.pdf Accessed March 16, 2011.