Plows and Carbon
The Timeline of Global Warming
By Max Wilbert
In June 1988, climatologist and NASA scientist James Hansen stood before the Energy and Natural Resources Committee in the United States Senate. The temperature was a sweltering 98 degrees.
"The earth is warmer in 1988 than at any time in the history of instrumental measurements,” Hansen said. “The global warming now is large enough that we can ascribe with a high degree of confidence a cause-and-effect relationship to the greenhouse effect… Our computer climate simulations indicate that the greenhouse effect is already large enough to begin to effect the probability of extreme events such as summer heat waves."
Hansen has authored some of the most influential scientific literature around climate change, and like the vast majority of climate scientists, has focused his work on the last 150 to 200 years – the period since the industrial revolution.
This period has been characterized by the widespread release of greenhouse gases like carbon dioxide (CO2) and methane (CH4), and by the clearing of land on a massive scale – the plowing of grasslands and felling of forests for cities and agricultural crops.
Now, the world is on the brink of catastrophic climate change. Hansen and other scientists warn us that if civilization continues to burn fossil fuels and clear landscapes, natural cycles may be disrupted to the point of complete ecosystem breakdown – a condition in which the planet is too hot to support life. Hansen calls this the Venus Syndrome, named after the boiling planet enshrouded in clouds of greenhouse gases.
"If we also burn the tar sands and tar shale [low grade, high carbon fossil fuels], I believe the Venus syndrome is a dead certainty,” Hansen has said.
If humanity wishes to have a chance of avoiding this fate, it is important that we understand global warming in detail. Why is it happening? When did it start? What fuels it? And, most importantly, what can stop it?
How old is global warming?
New studies are showing that the current episode of global warming may be a great deal older than previously believed - which may entirely change our strategy to stop it.
While fossil fuels have only been burned on a large scale for 200 years, land clearance has been a defining characteristic of civilizations – cultures based around cities and agriculture – since they first emerged around 8,000 years ago.
This land clearance has impacts on global climate. When a forest ecosystem is converted to agriculture, more than two thirds of the carbon that was stored in that forest is lost, and additional carbon stored in soils rich in organic materials will continue to be lost to the atmosphere as erosion accelerates.
Modern science may give us an idea of the magnitude of the climate impact of this pre-industrial land clearance. Over the past several decades of climate research, there has been an increasing focus on the impact of land clearance on modern global warming. The Intergovernmental Panel on Climate Change, in it’s 2004 report, attributed 17% of global emissions to cutting forests and destroying grasslands – a number which does not include the loss of future carbon storage or emissions directly related to this land clearance, such as methane released from rice paddies or fossil fuels burnt for heavy equipment.
Some studies show that 50% of the global warming in the United States can be attributed to land clearance – a number that reflects the inordinate impact that changes in land use can have on temperatures, primarily by reducing shade cover and evapotranspiration (the process whereby a good-sized tree puts out thousands of gallons of water into the atmosphere on a hot summer day – their equivalent to our sweating).
So if intensive land clearance has been going on for thousands of years, has it contributed to global warming? Is there a record of the impacts of civilization in the global climate itself?
10,000 years of Climate Change
According to author Lierre Keith, the answer is a resounding yes. Around 10,000 years ago, humans began to cultivate crops. This is the period referred to as the beginning of civilization, and, according to the Keith and other scholars such as David Montgomery, a soil scientist at the University of Washington, it marked the beginning of land clearance and soil erosion on a scale never seen before – and led to massive carbon emissions.
“In Lebanon (and then Greece, and then Italy) the story of civilization is laid bare as the rocky hills,” Keith writes. “Agriculture, hierarchy, deforestation, topsoil loss, militarism, and imperialism became an intensifying feedback loop that ended with the collapse of a bioregion [the Mediterranean basin] that will most likely not recover until after the next ice age.”
Montgomery writes, in his excellent book Dirt: The Erosion of Civilizations, that the agriculture that followed logging and land clearance led to those rocky hills noted by Keith.
“It is my contention that the invention of [agriculture] fundamentally altered the balance between soil production and soil erosion – dramatically increasing soil erosion.
Other researchers, like Jed Kaplan and his team from the Avre Group at the Ecole Polytechnique Fédérale de Lausanne in Switzerland, have affirmed that preindustrial land clearance has had a massive impact on the landscape.
“It is certain that the forests of many European countries were substantially cleared before the Industrial Revolution,” they write in a 2009 study.
Their data shows that forest cover declined from 35% to 0% in Ireland over the 2800 years before the beginning of the Industrial Revolution. The situation was similar in Norway, Finland, Iceland, where 100% of the arable land was cleared before 1850.
Similarly, the world’s grasslands have been largely destroyed: plowed under for fields of wheat and corn, or buried under spreading pavement. The grain belt, which stretches across the Great Plains of the United States and Canada, and across much of Eastern Europe, southern Russia, and northern China, has decimated the endless fields of constantly shifting native grasses.
The same process is moving inexorably towards its conclusion in the south, in the pampas of Argentina and in the Sahel in Africa. Thousands of species, each uniquely adapted to the grasslands that they call home, are being driven to extinction.
“Agriculture in any form is inherently unsustainable,” writes permaculture expert Toby Hemenway. “We can pass laws to stop some of the harm agriculture does, but these rules will reduce harvests. As soon as food gets tight, the laws will be repealed. There are no structural constraints on agriculture's ecologically damaging tendencies.”
As Hemenway notes, the massive global population is essentially dependent on agriculture for survival, which makes political change a difficult proposition at best. The seriousness of this problem is not to be underestimated. Seven billion people are dependent on a food system - agricultural civilization - that is killing the planet.
The primary proponent of the hypothesis - that human impacts on climate are as old as civilization - has been Dr. William Ruddiman, a retired professor at the University of Virginia. The theory is often called Ruddiman’s Hypothesis, or, alternately, the Early Anthropocene Hypothesis.
Ruddiman’s research, which relies heavily on atmospheric data from gases trapped in thick ice sheets in Antarctica and Greenland, shows that around 11,000 years ago carbon dioxide levels in the atmosphere began to decline as part of a natural cycle related to the end of the last Ice Age. This reflected a natural pattern that has been seen after previous ice ages.
This decline continued until around 8000 years ago, when the natural trend of declining carbon dioxide turned around, and greenhouse gases began to rise. This coincides with the spread of civilization across more territory in China, India, North Africa, the Middle East, and certain other regions.
Ruddiman’s data shows that deforestation over the next several thousand years released 350 Gigatonnes of carbon into the atmosphere, an amount nearly equal to what has been released since the Industrial Revolution. The figure is corroborated by the research of Kaplan and his team.
Around 5000 years ago, cultures in East and Southeast Asia began to cultivate rice in paddies – irrigated fields constantly submerged in water. Like an artificial wetland, rice patties create an anaerobic environment, where bacteria metabolizing carbon-based substances (like dead plants) release methane instead of carbon dioxide and the byproduct of their consumption. Ruddiman points to a spike in atmospheric methane preserved in ice cores around 5000 years ago as further evidence of warming due to agriculture.
Some other researchers, like R. Max Holmes from the Woods Hole Research Institute and Andrew Bunn, a climate scientist from Western Washington University, believe that evidence is simply not conclusive. Data around the length of interglacial periods and the exact details of carbon dioxide and methane trends is not detailed enough to make a firm conclusion, they assert. Regardless, it is certain that the pre-industrial impact of civilized humans on the planet was substantial.
“Our data show very substantial amounts of human impact on the environment over thousands of years,” Kaplan said. “That impact really needs to be taken into account when we think about the carbon cycle and greenhouse gases.”
Restoring Grasslands: a strategy for survival
If the destruction of grasslands and forests signals the beginning of the end for the planet’s climate, some believe that the restoration of these natural communities could mean salvation.
Beyond their beauty and inherent worth, intact grasslands supply a great deal to humankind. Many pastoral cultures subsist entirely on the animal protein that is so abundant in healthy grasslands. In North America, the rangelands that once sustained more than 60 million Bison (and at least as many pronghorn antelope, along with large populations of elk, bear, deer, and many others) now support fewer than 45 million cattle – animals ill-adapted to the ecosystem, who damage their surroundings instead of contributing to them.
Healthy populations of herbivores also contribute to carbon sequestration in grassland soils by increasing nutrient recycling, a powerful effect that allows these natural communities to regulate world climate. They also encourage root growth, which sequesters more carbon in the soil.
Just as herbivores cannot survive without grass, and grass cannot thrive without herbivores.
Grasslands are so potent in their ability to pull carbon dioxide out of the atmosphere that some believe restoring natural grasslands could be one of the most effective tools in the fight against runaway global warming.
“Grass is so good at building [carbon rich] soil that repairing 75 percent of the planet’s rangelands would bring atmospheric CO2 to under 330 ppm in 15 years or less,” Lierre Keith writes.
The implications of this are immense. It means, quite simply, that one of the best ways to reduce greenhouse gases in the atmosphere is to move away from agriculture, which is based upon the destruction of forests and grasslands, and towards other means of subsistence. It means moving away from a way of life 10,000 years old. It means rethinking the entire structure of our food system – in some ways, the entire structure of our culture.
Some ambitious, visionary individuals are working in parallel with this strategy, racing against time to restore grasslands and to stabilize Earth’s climate.
In Russia, in the remote northeastern Siberian state of Yakutia, a scientist named Sergei Zimov has an ambitious plan to recreate a vast grassland – a landscape upon whom millions of herbivores such as mammoths, wild horses, reindeer, bison, and musk oxen fed and roamed until the end of the last ice age.
“In future, to preserve the permafrost, we only need to bring herbivores,” says Zimov. “Why is this useful? For one, the possibility to reconstruct a beautiful [grassland] ecosystem. It is important for climate stability. If the permafrost melts, a lot of greenhouse gases will be emitted from these soils.”
Zimov’s project is nicknamed “Pleistocene Park,” and stretches across a vast region of shrubs and mosses, low productivity communities called ‘Taiga’. But until 12,000 years ago, this landscape was highly productive pastures for a span of 35,000 years, hosting vast herds of grazers and their predators.
“Most small bones don’t survive because of the permafrost,” says Sergei Zimov. “[But] the density of skeletons in this sediment, here and all across these lowlands: 1,000 skeletons of mammoth, 20,000 skeletons of bison, 30,000 skeletons of horses, and about 85,000 skeletons of reindeer, 200 skeletons of musk-ox, and also tigers [per square kilometer].”
These herds of grazers no only supported predators, but also preserved the permafrost beneath their feet, soils that now contain 5 times as much carbon as all the rainforests of Earth. According to Zimov, the winter foraging behavior of these herbivores was the mechanism of preservation.
“In winter, everything is covered in snow,” Zimov says. “If there are 30 horses per square kilometer, they will trample the snow, which is a very good thermal insulator. If they trample in the snow, the permafrost will be much colder in wintertime. The introduction of herbivores can reduce the temperatures in the permafrost and slow down the thawing.”
In the Great Plains of the United States and Canada, a similar plan to restore the landscape and rewild the countryside has emerged. The brainchild of Deborah and Frank Popper, the plan calls for the gradual acquisition of range lands and agricultural lands across the West and Midwest, with the eventual goal of creating a vast nature preserve called the Buffalo Commons, 10-20 million acres of wilderness, an area 10 times the size of the largest National Park in the United States (Wrangell-St. Elias National Park in Alaska).
In this proposed park, the Popper’s envision a vast native grassland, with predators following wandering herds of American Bison and other grazers who follow the shifting grasses who follow the fickle rains. The shifting nature of the terrain in the Great Plains requires space, and this project would provide it in tracts not seen for hundreds of years.
In parts of Montana, the work has already begun. Many landowners have sold their farms to private conservation groups to fill in the gaps between isolated sections of large public lands. Many Indian tribes across the United States and Southern Canada are also working to restore Bison, who not only provide high quality, healthy, traditional food but also contribute to biodiversity and restore the health of the grasslands through behavior such a wallowing, which creates small wetlands.
Grasslands have the power to not only restore biodiversity and serve as a rich, nutrient-dense source of food, but also to stabilize global climate. The soils of the world cannot survive agricultural civilizations for much longer. If the plows continue their incessant work, this culture will eventually go the way of the Easter Islanders, the Maya, the Greeks, the Macedonians, the Harrapans, or the Roman Empire – blowing in the wind, clouding the rivers. Our air is thick with the remnants of ancient soils, getting long overdue revenge for their past mistreatment.
The land does not want fields. It wants Bison back. It wants grasslands, forests, wetlands, birds. It wants humans back, humans who know how to live in a good way, in relationship with the soil and the land and all the others. The land wants balance, and we can help. We can tend the wild and move towards other means of feeding ourselves, as our old ancestors have done for long years. It is the only strategy that takes into account the needs of the natural world, the needs for a land free of plows and tractor-combines.
In time, with luck and hard work, that ancient carbon will be pulled from the atmosphere – slowly at first, but then with gathering speed. The metrics of success are clear: a calmed climate, rivers running free, biodiversity rebounding. The task of achieving that success is a great challenge, but guided by those who believe in restoring the soil, we can undo 8,000 of mistakes, and finally begin to live again as a species like any other, nestled in our home, at peace and in balance, freed at last from the burdens of our ancestors mistakes.
Climate meddling dates back 8,000 years. By Alexandra Witze. April 23rd, 2011. Science News. http://www.sciencenews.org/view/generic/id/71932/title/Climate_meddling_dates_back_8%2C000_years#video
U.S. Environmental Protection Agency. Global Emissions. Accessed June 23rd, 2012. http://epa.gov/climatechange/ghgemissions/global.html
The prehistoric and preindustrial deforestation of Europe. By Kaplan et al. Avre Group, Ecole Polytechnique Federale de Lausanne. Quaternary Science Reviews 28 (2009) 3016-3034.
‘Land Use as Climate Change Mitigation.’ Stone, Brian Jr. Environmental Science and Technology 43, 9052-9056. 11/2009.
‘Functional Aspects of Soil Animal Diversity in Agricultural Grasslands’ by Bardgett et al. Applied Soil Ecology, 10 (1998) 263-276.
Zimov, Sergei. Personal Interviews, June/July 2010.
Climate Emergency Institute
Climate Science Library