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Carbon Production = Oxygen Consumption (PS Oxygen supplies are limited.)
Each molecule of gas we burn removes 25 atoms of oxygen from our precious and dwindling supplies. There are many additional threats to the oxygen we need. To learn what is at stake and what can be done, please read on and then take action. We can reverse this deadly process!
Global warming projections, based on our ever increasing carbon output, all seem to overlook one very simple and important part of the calculation: oxygen consumption. We can’t keep pouring out carbon forever; not without using up our oxygen supply. Oxygen is consumed by all of our combustion technologies. Whether we are burning gas or wood for heating or cooking, driving a motorized vehicle (no matter what fuel), or firing up a coal burning electric generation plant—we are consuming oxygen. In fact, it is this consumption of oxygen that produces atmospheric carbon in the first place. 
Humans have employed combustion since the very first moment some brilliant individual figured out how to stay warm near a fire. From there we learned to bank a fire, keep coals alive, transport them from place to place, and then to start fire at will. We eventually learned to make stone fireplaces, kilns and forges, steam engines , and finally; the internal combustion engine . Along the way, we have substantially replaced wood and charcoal with coal and petroleum—for better or for worse.
Fossil fuels burn in much the same way as wood and other plant materials do. Fire begins whenever a dry (or gaseous material) high in flammable compounds is heated to its “flash point” in the presence of oxygen. The flash point is the temperature at which the chemical components of the material begin to vaporize. Once this temperature is reached (through a lightning strike or, say, in a coal fired plant that produces electricity) the carbon in the material begins to chemically combine with oxygen and we have combustion. The result that we have been hearing a lot about is more carbon in our atmosphere. The other result, that hasn’t been getting as much press: less free breathable oxygen. In fact, for every atom of carbon released into the atmosphere, at least two atoms of breathable oxygen are lost. (Three or more atoms of free oxygen are lost if the carbon atoms are bound to hydrogen, as they often are when fossil fuels are involved.) 
Oxygen, as we know, is necessary for life. (Well, maybe not all life, science has uncovered organisms that don’t even like oxygen, but it is essential to the lives we care about most.)  The oxygen we need is not a given constant commodity. The amount of oxygen in our atmosphere has varied greatly over earth’s history.  In fact, it is believed that there was no free oxygen at all, until the first photosynthesizing cyanobacteria began exhaling.  While we will never know with certainty when this first happened, it was a very long time ago. Estimates vary from 2.3 to 3.9 billion years ago.  Since that time oxygen levels are estimated to have reached as high as 30% of the earth’s atmosphere (during the early Permian period), only to crash down to about 12% (10 million years into the Triassic period).  That crash took 20 million years; however it still happened too quickly for most oxygen breathers to adapt. One of the earth’s largest extinction events, and longest recovery periods accompanied this crash in free oxygen.  Fortunately, for us, cyanobacteria and abundant plant life saved the day, freeing oxygen from carbon dioxide and making the air fit to breathe.
Free oxygen is manufactured by photosynthesis. In our modern world—as opposed to ancient geological history—that is primarily the job of green plants, rather than bacteria. The oxygen we breathe and burn is made by plants.  And in case you haven’t heard—those plants are in peril.
The reduction of habitat for oxygen-producing plants (that we are experiencing today) probably started with the desertification of the middle-east.  Mesopotamia, known as the birthplace of western civilization, was once one of the most fertile, lush environments on the planet.  It was located in the area that is now known as Iraq, and included parts of what became modern day Syria, Turkey, and Iran.  This area now includes some of the most inhospitable deserts on our planet. Desertification is often blamed on human activities—primarily cutting down trees, removing vegetation, excessive soil impacts (such as plowing and over grazing), and the over utilization of water resources. Current official estimates for the desertification of our planet are between 6 and 12 million square kilometers.  Official estimates may actually under report desertification; but in any event, the trend is continuing. Desertification reduces the land’s ability to support oxygen-producing plants on a long term or possibly even permanent basis.
Deforestation contributes to desertification, in addition to directly reducing the number of trees producing oxygen.  It is estimated that about 50% of the world’s forests have already been removed. While we have 4 billion hectares of forest left, even with conservation, replanting, and urban tree planting programs, we are still losing 13 million hectares a year.  In addition to the loss of oxygen-producing trees, deforestation directly causes the loss of topsoil, which reduces potential production of oxygen in at least two additional ways.
Nearly all life is dependent on topsoil. The very molecules that make up our bodies were originally absorbed by plants from topsoil. We are dependent on topsoil for the food we eat, and for the oxygen we breathe. Topsoil is the place where the nutrients plants depend on—to do their important work—are stored, exchanged, and cycled. When forests and woodlands are cut down and when brush and grasslands are cleared—topsoil begins to erode by actions of wind and rain.  The soil microorganisms that are responsible for preserving and cycling nutrients need protection from the sun. Deforestation and clearing expose the soil to the harmful effects of sunlight, killing microorganisms, and reducing the remaining soil’s ability to support life. 
Topsoil is also degraded by large scale commercial agriculture practices.  Plowing and the application of herbicides also bares the soil, allowing it to be carried away by the wind, rain, and irrigation water. In addition, clearing and plowing exposes the decomposed organic matter, known as humus, to sunlight and oxygen—thereby causing oxidation.  This oxidation process depletes topsoil further; and it binds free oxygen with carbon, reducing the breathable oxygen in our atmosphere. (Similarly, slash and burn agriculture degrades soils and encourages erosion and topsoil loss, while directly increasing carbon and reducing oxygen.) Fifty percent of the world’s habitable land is now dedicated to agriculture and pasture and is at risk from poor practices.  Most of the rest of the habitable land is covered with buildings, asphalt, and concrete. However, this does not protect the soil. Urban environments also contribute to topsoil loss and carbon production. Unless they have vigorous tree planting and tending programs, they do not contribute to oxygen production. Urban construction projects and the use of herbicides bare the soil, contributing to soil erosion and the resultant sedimentation which we will be considering shortly. Topsoil losses around the world are estimated to range from 10-40 percent per year. 
Topsoil erosion, whether from deforestation, plowing and overgrazing, construction projects, or herbicide use—contributes tons of sediment to rivers and streams, lakes and ponds, and the ocean—every single year. This erosion and sedimentation (which is the result of direct action against oxygen-producing plants) not only reduces the oxygen producing potential of the land, it also reduces the oxygen producing capabilities of aquatic environments. Sediment clouds water, reducing its light-passing capabilities. When the sediment settles, it suffocates plants.  Meanwhile, the sediment changes the aquatic environment, often preventing the plants from reestablishing themselves in areas where they once thrived.  So we see that loss of topsoil from deforestation and other causes reduces potential oxygen production by (1) destroying the topsoil needed for healthy terrestrial plant growth, and (2) reducing light for, and causing suffocation of, native plants growing in aquatic environments. We should be beginning to see how everything is connected; however, we aren’t done yet. The loss of topsoil has another detrimental effect on oxygen production.
Ongoing topsoil degradation has reduced the yield commercial farmers can get from their land; unless they add supplemental fertilizer. Meanwhile, the demand on farmers to produce ever higher yields because of growing world populations and the use of agricultural products for fuel has increased. Governmental advisors, as well as chemical company sales people, all promise those higher yields through chemistry.  Huge amounts of chemical fertilizers are now applied to most commercial farm land.  For example, The Fertilizer Institute estimates that in 2005 “9.5 million . . . tons of fertilizer” were used to grow commercial corn in the United States—and that is just one crop. The result of all the commercial fertilizer use is a phenomenon called nutrient runoff. 
Plants were not designed by nature to live on synthetic fertilizers. They are not efficient at absorbing them from the soil. Much of the fertilizer ends up being carried into streams, lakes, rivers, and eventually into the ocean. The nutrients then upset the ecological balance of our water ways and the ocean and lead to the proliferation of algae on the water’s surface. This algae blocks light from reaching the native plants that live below the water’s surface, causing plant death and a drastic reduction in oxygenation. As the plants and animals die, their decomposition consumes any available oxygen and the death spreads. This process is called eutrophication. Over half of the water ways in Asia and Europe are considered eutrophic. Lakes in the Americas are only doing slightly better, where nearly half are eutrophic. In the ocean, near inhabited coastlines, the effects of nutrient runoff are commonly called dead zones. As of 2008, 405 dead zones had been surveyed. Some were as small as a square kilometer; however, the largest covered 70,000 square kilometers.  These areas no longer produce much oxygen, and they are growing.
With all these assaults on our oxygen supply, we should not be surprised to learn that the levels of free oxygen are declining.  Even though simple common sense points in that direction, we tend to be shocked when we learn that, through our choices, we are undoing the perfect balance that nature took so long to achieve. Surveys of our oxygen levels over the last 20 years show that we have decreased atmospheric oxygen by .03%. That might not seem like much, but when one realizes that the oxygen drop that precipitated one of the largest extinction events only averaged .000,000,9% per year—or about .000,001,8% over a 20 year period, that little .03% begins to look significant.
We can also look at this figure another way. Oxygen is generally reported as being 20.95% of the atmosphere. It is also very well documented that we begin to show signs of oxygen deprivation at levels below 19.5%. If oxygen levels continue to decrease at the rates they have for the last 20 years, we will be below that 19.5% threshold in less than 250 years. However, the rate of oxygen decline is expected to increase, through increased carbon emissions, desertification, deforestation, eutrophication, and ocean dead zones. Right this minute, new dead zones are growing rapidly in the Gulf of Mexico.  And there are other threats to our oxygen supply.
Remember the 20 million year long oxygen drop (from early Permian period into the Triassic period)? No one was burning coal or driving cars back in those days. The oxygen drop way back then was caused by mineral oxidation. The world was very tectonically and volcanically active, and all that activity brought new unoxidized minerals to the surface where water, the sun, and oxygen could work on them. Over time, the minerals oxidized, corroded, and rusted—binding free oxygen and removing it from the atmosphere ; until many long eons later when bacteria, plant roots, and photosynthesis were able to set it free once again. Do we need to think about mineral oxidation in today’s world? Yes we do. Not only does the planet remain tectonically and volcanically active, human activity has vastly increased the minerals available to oxidize. Construction, plowing, deforestation, and herbicides bare our precious mineral rich soils and allow them to oxidize. More significantly, however, mining brings rich mineral deposits, that were protected from oxygen deep within the earth, to the surface. These deposits are then pulverized and treated to remove whatever is of monetary value. The waste is left in piles or ponds to oxidize, reducing breathable oxygen. Sometimes, this material pollutes our waterways; where it will continue to oxidize, removing and binding oxygen dissolved in the water, in addition to any toxic and suffocation effects that it may also have on our waterways and their photosynthesizing plants.
Take a deep breath of sweet air. It is up to us to ensure that two hundred and fifty years from now there will still be enough oxygen to take another breath of this sweet, sweet air. Think about the young people, those growing up who have not yet started thinking about having their own families. The great, great grand children of the young people alive now may live to see the day when the earth’s atmosphere will no longer support human life. If this comes to pass, it will be because of our choices. It is up to us, all of us, to do something. There is no better place to begin than by planting trees.
The Arbor Day Foundation provides many resources for individuals and communities. They publish an informative newsletter for their members; and they sponsor urban tree planting programs as well as efforts to save our remaining forests. Please visit their web site at http://www.arborday.org and get involved.
There are many ways we can help raise our oxygen levels. Supporting local, sustainable, and organic agriculture is good for us, good for the planet, and good for our next breath of air. An easy to read book, Food Security & Sustainability for the Times Ahead,  provides many resources for families and individuals who want to get involved with the sustainable food movement. Walk, ride a bike, or use public transportation whenever possible—it will save money, save carbon, but most important of all—it will help save our precious oxygen. Turn the thermostat down in the winter and up in the summer. (Nearly 70% of our electricity here in the United States comes from burning fossil fuels. In some other countries the rate is even higher.)  Plant something green and photosynthesizing, even if you only have room for a few potted plants in a bright window. Every green plant makes oxygen. We depend on them. Let’s prove they can depend on us.
Harvest McCampbell is the author of "Food Security & Sustainability for the Times Ahead." She offers consultations and presentations for groups and organizations. Please see http://www.BioDiverseGardens.com for more information.
References, sources, and research notes:
 How fire Works: http://science.howstuffworks.com/fire1.htm
 Steam Engine History: http://en.wikipedia.org/wiki/Steam_engine#History
 Internal Combustion Engine Time line:
 Some ratios are given for hydrocarbon combustions: http://en.wikipedia.org/wiki/Combustion
Also see: Estimates of oxygen loss from burning fossil fuels:
C8H18 + 12.5 O2 --> 8 CO2 + 9 H2O –This is the formula for the combustion of gasoline from the page above. Eight carbon atoms and 18 hydrogen atoms consume 25 oxygen atoms and produce eight carbon dioxide molecules and nine water molecules. For every molecule of gasoline we burn we add only 8 carbon atoms to the atmosphere, but we lose 25 atoms of free breathable oxygen.
 Life without Oxygen: http://serc.carleton.edu/microbelife/extreme/withoutoxygen/index.html
 Oxygen levels have varied widely over earth’s history:
This site talks about mineral interaction with oxygen—and it is interesting to ponder all the mining we do—which exposes more mineral material to the air—which can then interact with oxygen—and thus trap it in mineral compounds. Metal refining and its eventual break down through rust and corrosion also consumes free oxygen.
 No free oxygen in early earth:
“When our planet formed some 4.5 billion years ago, virtually all the oxygen on Earth was chemically bound to other elements. It was in solid compounds like quartz and other silicate minerals, in liquid compounds like water, and in gaseous compounds like sulfur dioxide and carbon dioxide . Free oxygen — the gas that allows us to breath, and which is essential to all advanced life — was practically non-existent.”
 First Oxygen:
 The Big die—Oxygen drop
“Atmospheric oxygen content, about 21 percent today, was a very rich 30 percent in the early Permian period. However, previous carbon-cycle modeling by Robert Berner at Yale University has calculated that atmospheric oxygen began plummeting soon after, reaching about 16 percent at the end of the Permian and bottoming out at less than 12 percent about 10 million years into the Triassic period.
"Oxygen dropped from its highest level to its lowest level ever in only 20 million years, which is quite rapid, and animals that once were able to cross mountain passes quite easily suddenly had their movements severely restricted," Huey said.”
See also: Oxygen levels for Late Devonian period—few or no fires, oxygen at 15.75%:
 “Photosynthesis is arguably the most important biochemical pathway, since nearly all life depends on it.” http://www.newworldencyclopedia.org/entry/Photosynthesis
 Mesopotamia, Location:
 Desertification—affects and areas:
 Deforestation figures—amount of land in forest and amount of forest being lost:
 Soil erosion—topsoil being lost between 10 – 40 % faster than it is formed:
 Decolonizing Soil: PowerPoint program on the importance of topsoil and its’ depletion in North America from the time of contact until the present day. Methods to reverse this process on the scale of the back yard and the community are shared.
 Percent of land in agriculture and pasture:
 Oxidation of humus when exposed to sun:
 Sedimentations effect on submerged vegetation, examples:
 Sedimentations effect on aquatic environments, general two web sites:
 Documentation for government advisors and chemical companies recommending synthetic fertilizers:
You Can Farm, Joel Salatin, published by Polyface, Inc.
A Sand County Almanac, Aldo Leopold, published by Oxford University Press (I highly recommend both of these books. They explain topsoil and nutrient cycles in a way most everyone can understand.)
 Average amount for fertilizer used in 1995 was 129 pounds per acre.
See also: http://en.wikipedia.org/wiki/Fertilizer
 Estimates of the amount of fertilizer used on crop land are very hard to find. On the following site, The Fertilizer Institute documents that in 2005 it is estimated that “9.5 million nutrient tons of fertilizer” were used to grow commercial corn in the United States.
 Effects of fertilizer on water ways:
 Oxygen levels dropping:
 Proliferation of oil eating microbes may have already caused two new dead zones in the gulf by consuming most of the dissolved oxygen. http://www2.nbc13.com/vtm/news/local/article/oil_spill_update_low_oxygen_found_in_2_areas_off_alabama_coast/159076/ See also: Hydrocarbon eating bacteria:
 This site talks about mineral interaction with oxygen—and it is interesting to ponder all the mining we do—which exposes more mineral material to the air—which can then interact with oxygen—and thus trap it in mineral compounds. Metal refining and its eventual break down through rust and corrosion also consumes free oxygen.
 Plant trees, save forests: http://www.arborday.org
 Food Security & Sustainability for the Times Ahead: http://www.harvestmccampbell.com/In_Print.htm
 Percentage of electricity from burning fossil fuels (69.5 %%) :
Chart clearly shows that most of our electricity is produced from burning fossil fuels:
Scroll down on the page below for another chart that gives the same figures:
More information on dropping oxygen levels and other related information:
Oxygen levels dropping faster than Carbon is rising:
Atmospheric Oxygen Levels Falling
The oxygen reduction is just 0.03 percent in the past 20 years
Estimates of oxygen loss from burning fossil fuels:
Declining oxygen levels—best site, it documents the importance of trees to our oxygen level:
We are breathing fossil oxygen!
“Right now, of course, the earth's oxygen level is falling every so slightly as the carbon dioxide concentration increases about 1.5 parts per million (ppm) each year. The carbon dioxide increase/oxygen decrease is due to deforestation and burning of fossil fuels. Thus, we are using some of the atmospheric oxygen added by ancient photosynthesis. Fossil fuels, such as coal, oil and natural gas represent carbon fixed by ancient photosynthesis.”
Commercial and medical oxygen is obtained by separation of oxygen from the air.