New research in the prestigious journal Nature estimates that “the global number of trees has fallen by approximately 46% since the start of human civilization.”
The study also suggests that about 15 billion trees are being cut down each year, and that the average age of forests has declined significantly over the last few thousand years.
The study was led by researchers at the Yale School of Forestry and Environmental Studies with contributions from scientists at universities and research institutions in Utah, Chile, the UK, Finland, Italy, France, Switzerland, New Zealand, The Netherlands, Germany, Czech Republic, Brazil, and China.
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 its 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 burned by heavy logging 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 before seen – 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, and 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 paddies 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.
Destruction of the land as the root
The anti-apartheid organizer Seve Biko wrote in the 1960’s that “One needs to understand the basics before setting up a remedy. A number of organizations now currently ‘fighting against apartheid’ are working on an oversimplified premise. They have taken a brief look at what is, and have diagnosed the problem incorrectly. They have almost completely forgotten about the side effects and have not even considered the root cause. Hence whatever is improved as a remedy will hardly cure the condition.”
The same could be said of much of the modern environmental movement. While coal, oil, and gas are without a doubt worthwhile targets for opposition, the “climate” movement has forgotten the primary importance of the meadows, the grasslands, the forests, the mountains, and the rivers.
Without this, the movement has been led astray. It’s no wonder that ineffective solutions and tepid reforms that actually strengthen global empire are being promoted, instead of what is actually needed: revolutionary overthrow of this system of power.
Image: CC BY-NC-ND 2.0, Kate Evans/CIFOR, https://www.flickr.com/photos/cifor/35035343564