~ Table of Contents ~
~ Abstract ~
~ [1] ~ Soil Chemistry Basics ~
~ [2] ~ Increasing Soil Organic Matter Contents in Tropical Soils ~
~ [3] ~ Terra Preta ~
~ [4] ~ Could terra preta eliminate, or significantly reduce, global warming? ~
~ [5] ~ Could carbon contents of the world's tropical cropland soils be increased sufficiently to significantly reduce global warming? ~
~ [6] ~ Slash-and-Burn vs. Slash-and-Char ~
~ [7] ~ Effects of Slash-and-Char on Tropical Rainforests ~
~ [8] ~ Potential Side Effects of Large-Scale Conversions to Terra Preta ~
~ [9] ~ The Possibility of Producing an Ice Age ~
~ [10] ~ Conclusions ~
~ Appendix I ~ Illegal Logging in Developing Countries: Some Insights ~
~ References ~

Previous Editions 1 (Sept. 2008)

Reference Citation Nomenclature: A typical reference citation such as (98K3) refers to a document published in 1998 and having a lead author with a last name beginning with "K." The final digit is a running index to make sure no two references are defined by the same citation.

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~ Abstract ~
The fundamental problem with most tropical soils is their low organic matter contents relative to relatively fertile temperate soils. As a result, nutrients in tropical soils tend to be leached out or mineralized, resulting in low fertilities and long fallow periods in tropical croplands and grazing lands. The solution to this problem was discovered by ancient Amazonian indian tribes thousands of years ago, and spread to 1-10% of Amazonia. However the technology was never transferred to European immigrants to the new world. The issue attracted international attention around 2001, resulting in soil scientists from around the world now working to discover how to replicate the large expanses of the still-fertile ancient soils ("Terra Preta") that Brazilians extract and sell. Success, though elusive, seems certain given the scientific capabilities of modern-day soil scientists relative to those of ancient indian tribes. Success would almost certainly reduce, or eliminate, the hunger being experienced by about 0.8 billion of the world's population, most of whom are part of the 75% of the world's population that live in tropical countries. There are doubts that the microorganisms essential for terra preta's success could survive in temperate climates. Success could also create an additional carbon sink far larger than that required to hold all current and future greenhouse gas emissions. Photosynthesis would draw these greenhouse gasses into the terra preta. Deforestation provides the primary threat to the success of large-scale creation of new terra preta. Terra Preta also offers the potential for greatly reducing the rate of loss of tropical rain forests to "slash-and-burn" agriculture.

~ Introduction ~
Soil science, even just the portion related to the sequestering of organic carbon in tropical soils, is a complex science. This author makes no claims regarding formal training in this field. The science you find below reflects only that assimilated during this author's three or so decades of review, analysis and data-compilation related to the degradation of the world's soils (07S2), croplands (07S2), forest lands (07S1), grazing lands (07S3), irrigated lands (07S4) and fisheries (07S5). The importance of soil science seems comparable with any other realm of human endeavor, so its complexities must be faced. Environmental determinism theory contends that the evolution of human cultures reflects primarily an adaptation to changing forms and degrees of environmental stress. The role of soils in determining the "changing forms and degrees of environmental stress" that human cultures have encountered is about as significant as that of any other factor that human cultures have had to deal with over the millennia. This is widely recognized, except perhaps in some political circles (08S4). Thus the low fertilities of tropical soils, relative to temperate soils, is seen as explaining the geography of the divide between the developing world and the developed world. Whatever conflicts are easily explained by including, in the developing world, the regions where soils have endured millennia of degradation at the hands of ancient civilization. Gradations of living standards are also explained and explainable in terms of soils. The resultant extreme economic bipolarity of human cultures in an environment of huge increases in the mobilities of virtually every element of economic activity is at the root of virtually all the problems the world now faces under the label of "globalization."

Any successful effort to understand, in scientific terms, the differences in fertilities between temperate and tropical soils could lead ultimately to technologies capable of diminishing these differences. The effects of doing this could clearly produce massive effects on the evolution of human cultures. It turns out that a technology for diminishing the fertility difference between temperate and tropical soils over very large areas was developed about 7000 years ago, not by brilliant soil scientists, but by primitive indian tribes in Amazonia (essentially all of modern-day Brazil). Many believe that this technology led to the development of an advanced civilization in the region - something that traditional "slash-and-burn" agriculture is incapable of. The technology was never transmitted to European settlers in Amazonia, perhaps as a result of European diseases wiping out these indian tribes. Modern man discovered evidence of this ancient technology around 1870, and this attracted widespread interest among soil scientists around 1950. Suddenly the massive ramifications of this ancient technology in terms of its ability to alter the evolution of human cultures worldwide struck these scientists. As a result, scientists from many parts of the world are now busy trying to reproduce the technology, including the ability to spread the fertile tropical soils over large areas.

One could compile a rather long list of the likely effects of the success of these soil scientists on the evolution of human cultures. Success seems virtually guaranteed, since one can hardly imagine a bunch of modern-day soil scientists being unable to accomplish what primitive tribes were able to accomplish. It now appears that among the first effects of this success on the evolution of human cultures will be the elimination of global warming. This is a result of the improved tropical soils creating a huge carbon sink, readily capable of capturing and sequestering the current excess of atmospheric greenhouse gasses plus any future releases. The likely side effects include huge economic benefits to developing nations, and probable major reductions in both human hunger and tropical rainforest deforestation. This would suggest that elimination of global warming could be accomplished at very low cost. None of the seriously considered strategies for dealing with global warming are physically and economically capable of addressing global warming. The forthcoming new soil sink for atmospheric greenhouse gasses is the only viable strategy.

~ [1] ~ Soil Chemistry Basics ~
Tropical soils are quite fertile in "closed" environments (in which nothing is harvested and transferred out of the system). This is because, for most tropical soils, fertility resides in the plant life growing on these soils and in the decaying leaves, stems, branches, trunks, roots and fruit of dead plants. When most tropical soils are converted to open environments, e.g. by harvesting fruits and vegetables, or removing grazing animals (e. g. beef cattle) or cutting and removing timber, soil fertilities degrade to a small fraction of what they were as closed systems. As a result, garden plots of tropical shifting cultivators must be abandoned (fallowed) after several years of use and left unused (operated as a closed system) for about two decades to allow soil fertilities to be restored. Most tropical grazing lands used for raising beef cattle etc. degrade to extremely low fertilities after 7-10 years. Then they must then be fallowed, probably for several decades. This difference between temperate and tropical soil fertilities is often seen as the reason why nations in temperate climates tend to be more advanced that tropical nations. This difference in soil fertilities, in combination with the higher population growth rates in tropical nations, probably explains why the bulk of the world's hunger is found in tropical nations. Today about 75% of the world's human population resides in tropical climates (06G1). This population (about 4.5 billion) is growing significantly faster than human populations in temperate climates, and about 0.8 of these 4.5 billion do not have enough to eat.

The basic reason for the difference in soil properties is that the organic matter contents of most tropical soils are roughly a third of what they are in most temperate soils. The useful forms of key soil nutrients (nitrogen, phosphorous, potassium, calcium, magnesium and other elements) are to be found associated with the soil organic matter. So with less soil organic matter these key nutrients tend to leach out into surface waters and ground waters draining the soil. Soil organic matter also increases the water-holding capacity of soils, increases their tilth, and provides numerous other benefits (See Section [B5] of Chapter 1 of Ref. (08S1)). The basic chemistry that explains the difference in soil organic matter contents seems to be that two fundamental chemical reactions compete for soil organic matter. One reaction involves the chemical bonding of soil organic matter with soil minerals, e.g. clay, to form organo-mineral complexes that are stable and long-lasting (between 100 and 1000 years depending on the chemical composition of the complex). The other chemical reaction is the "mineralization" of soil organic matter. This typically involves combining chemically with oxygen to form CO₂ that then leaves the soil (94T1). It could also involve combining chemically with potassium to form some non-organo-mineral complexes that then leach into the groundwater or surface water.

The formation of organo-mineral complexes makes the soil more fertile as a result of the stable organo-mineral complexes remaining in the soil, effectively increasing the soil organic matter content. The second ("mineralization") reaction contributes nothing to soil fertility since the reaction products leave the soil and go into the air, surface waters, or ground waters. Apparently "mineralization" proceeds at a faster rate than the formation of organo-mineral complexes at higher temperatures (typical of tropical climates), and at a slower rate at lower temperatures (typical of temperate climates). This apparently explains the higher soil organic carbon contents in temperate soils than in tropical soils - and thus the high fertilities of most temperate soils, and the low fertilities of most tropical soils. Toxicity effects due to elements such as iron and aluminum also plague tropical soils. These two basic competing chemical reactions have obviously played major roles in determining the course of human history. This should not be surprising. After all, organo-mineral complexes are the primary link between the mineral world and the organic (living) world, and "mineralization" is the primary process by which mankind converts energy resources into useful ends.

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~ [2] ~ Increasing Soil Organic Matter Contents in Tropical Soils ~
If some way could be found to increase soil organic matter contents of tropical soils, making them more fertile and therefore more similar to temperate soils, the effects on mankind would be both profound and positive. The economies of developing nations could be significantly enhanced since 50-75% of the economies of these nations are agriculture-related. It can also be shown (See below) that it may be possible to eliminate global warming - profitably or at low cost - and that this process is probably the only financially feasible way of eliminating global warming. Increasing soil organic matter contents in tropical soils may seem impossible since the two competing chemical reactions that determine soil organic matter contents seem so fundamental as to be immune from manipulation by humans.

~ [3] ~ Terra Preta ~
It turns out that achieving high soil organic matter contents in tropical soils and maintaining them indefinitely is difficult, but far from impossible. Ancient (500 to 7000 years ago (06G1)) indian tribes in Amazonia (the Amazon River basin - now essentially most of Brazil) apparently stumbled on a way of accomplishing this. Realizing the implications of their discovery, they proceeded to perfect the process and spread the knowledge of the process throughout ancient Amazonia. Some believe the knowledge and the fertile soil spread to 10% of Amazonia (i.e. an area about the size of France) (99W1). Others estimate only 1% or more (63,000 km² or more of forested lowlands) (03S1) (04D1). Unfortunately, knowledge of the soil enhancement process never got transmitted to European newcomers to Amazonia. Had that communications failure not occurred, the social, political and economic differences between the developed world and the developing world might have been far smaller than they are today. The first published mention of fertile "dark earth" in Amazonia was in 1870 by James Orton of Vassar (04D1). However the significance of terra preta (Portuguese for "dark earth") in Amazonia did not achieve international awareness until 2001-2002 (04D1).

Throughout Amazonia one finds countless patches, roughly 50 acres (0.2 km²) in size, of fertile soil with depths of up to about 2.0 meters (04D1). Patches 350 to 500 km² in size have also been found (04D1). Modern-day Brazilians extract this fertile "terra preta" (a fine dark loam) and sell it. It is even sold in some U.S. garden stores, although there are doubts as to whether the key microorganisms in terra preta can tolerate low temperatures (08S3). (Other names for terra preta are "Amazonian Dark Earths" or "Indian Black Earth.") These fertile patches of terra preta are surrounded by typically low-fertility tropical soils. (Terra preta contains three times as much phosphorous and nitrogen as surrounding soils.) Converting ordinary tropical soils into terra preta can double or triple crop yields (06B1). Some studies find that the soil organic matter content (in units of grams of organic carbon per unit area of soil) of terra preta is about 50 times greater than that found in typical low fertility tropical soils (08L1). (Other data noted below indicate ratios of 20 and 25.) Another study found the (organic) carbon content of terra preta to be up to 9%, compared with 0.5% in nearby tropical soils (99W1). However terra preta soil thicknesses are several times greater than typical low-fertility tropical soils so these two data are roughly consistent. These data suggest that the soil organic matter content of terra preta is about 17 times greater than in typical, fertile temperate soils on a carbon-per-unit-area basis. (To convert soil organic carbon content data to soil organic matter content, multiply by a factor of about 2.)

A major advantage of terra preta is that tropical rains don't leach nutrients from fields of terra preta soil (08R1). Because low-fertility tropical soils contain little organic matter for nutrients to hang on to, tropical rains tend to leach out soil nutrients. Another major (and astounding) advantage of terra preta is its apparent ability to "self-propagate." So when people dig up two thirds of a 2-ft.-thick layer of terra preta (to sell), the remaining one third expands its depth, creating more terra preta over time. This explains why terra preta soils are often 1-2 meters deep, far deeper that global average topsoil thicknesses (about 0.25 meter). No Indian tribe, or modern-day farmer, would bother to create topsoil depths of 1-2 meters, since root depths of plants used for food rarely exceed 0.25 meter. This ability to "self-propagate" is believed by some to arise from special breeds of microorganisms that are able to generate additional terra preta (somewhat like sourdough bread) (07E1). Apparently, at some threshold level, terra preta attains the capacity to perpetuate (regenerate) itself and behaves more like a living "super" organism than an inert material (08R1). Some authors dispute the "super organism" theory (06G1), but this leaves the explanation of the often-encountered, abnormally large thicknesses of terra preta unknown. These doubts may have merit. Microorganisms might very well be able to migrate deeper down into the soil on their own, perhaps as a result of water percolating through the soil. But those bits of "char-wood" (also essential ingredients of terra preta) almost certainly cannot migrate on their own. They could only be inserted into the soil by conscious acts of humans. One possible way of sorting out this confusion is to assume that, for whatever unknown reason, humans inserted "char-wood" deep into the land, but when they inserted all sorts of organic matter (another key ingredient of terra preta) later on, they did not insert it as deep. This could be a logical result of having lots of "char-wood" available at one time (e.g. after forest clearing) but organic matter (e.g. crop residues, food scraps, feces etc), another key ingredient of terra preta, is only accumulated gradually. The apparent ability of terra preta to "self-propagate" could be nothing more that an artifact of this.

Making use of all those benefits of terra preta requires a way of converting low-fertility tropical soils into terra preta on a large scale like those ancient Indian tribes did. Soil scientists from numerous nations are now working on the problem, and the International Bio-char Initiative has been created to coordinate the various studies of the science behind terra preta. If the implications of this research were more widely know (hunger- and poverty reduction in the tropical world, and elimination of global warming), the world's governments would probably fund these studies far better. (Brazil would become one of the world's wealthiest nations.) Success seems almost assured, however, because it is hard to imagine that modern-day soil scientists cannot repeat what primitive indian tribes were able to accomplish. However it seems clear that success could be difficult. This is partly because it is obvious that soil microorganisms play a key, but poorly understood, role. When Indian tribes migrated they apparently took along with them samples of terra preta (somewhat like sourdough bread) that they inserted into the soil of their destination (08R1) (07E1). This apparently assisted in spreading the key microorganisms into the soils of their new home.

By far the most important hint as to just how terra preta increases soil fertilities is that it contains large amounts of charred wood ("char-wood") in small pieces. This material is essentially charcoal, but it is produced by burning wood or crop residues (not coal) in an oxygen-poor environment (a process called "pyrolysis"). These bits of "char-wood" date back as far as 7000 years before the present. (Charcoal has a half-life in soils of 5000 years, and there is no apparent reason why "char-wood" would have a much shorter half-life.) Food scraps, bones of small animals, human excrement, and assorted other types of organic matter were mixed with the "char-wood" by those ancient indian tribes. The charred wood buried in the soil probably came from cooking fires. (Some of the firewood there would be burned in an oxygen-poor environment, producing char rather than being converted to CO₂ and ash.) Char-wood is very porous, and the tiny pores provide lots of surface area. (One ton of charcoal has a surface area of 625 square miles (400,000 acres) and there is no apparent reason why "char-wood" would have much less.) Apparently this huge amount of surface area provides sites for the formation of organo-mineral complexes discussed earlier. These complexes keep soil organic matter and the nutrients in it from being "mineralized" (e.g. converted to CO₂) or leached out of the soil into the groundwater. (Many soil clays have atomic-scale tunnels that also provide interior surface sites for the formation of organo-mineral complexes in soils where the rate of "mineralization" is slow enough to permit this to happen - mainly in temperate soils. Apparently the rate of formation of organo-mineral complexes in "char-wood" in tropical climates is significantly greater than in clays. This might reflect the fact that pore sizes in "char-wood" are significantly larger.)

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~ [4] ~ Could terra preta eliminate, or significantly reduce, global warming? ~
The earth's atmosphere contained 380 parts per million of carbon in 2007. This is equivalent to 760 Gt. (giga-tonnes) (billions of metric tons) of carbon, largely in the form of carbon dioxide and methane (Both are greenhouse gasses.). Some fraction of this 760 Gt. of carbon must be removed from the atmosphere if the global warming problem is to be significantly reduced or eliminated. In addition, the bulk of whatever greenhouse gasses the combustion of fossil fuels sends into the atmosphere in the future must be removed. To create a "carbon-negative" world in which CO₂ withdrawals from the atmosphere exceed the rate at which fossil fuels combustion sends it into the atmosphere currently requires a removal rate of 6.1 Gt. of CO₂ per year (04O1). Another calculation gives 9.5 Gt. of CO₂ per year (04L1). This requires some sort of terrestrial sink capable of gathering massive amounts of carbon (mainly in the form of CO₂) from the atmosphere and storing that carbon permanently in some other sink. Soil is the most obvious sink since the world's total inventory of soil organic carbon is about 82% of the global organic carbon in terrestrial ecosystems. Terra preta performs the carbon-collection/ storage task by the process of photosynthesis in existing live plants. Dead vegetation and crop residues are then incorporated into the soil. The question of the permanence of this storage is addressed below. Terra preta also performs its function as a carbon sink by receiving crop residues, human excrements, food wastes and all sorts of other carbon-containing (organic) wastes that humans bury in the soils. No other strategy for stabilizing, or reducing, global warming is capable of pulling already-existing greenhouse gasses out of the atmosphere (See below.). However oceans absorb greenhouse gasses from the atmosphere, but only at a rate significantly lower that the current rate at which fossil fuels combustion releases it to the atmosphere.

One alternative concept for reducing atmospheric greenhouse gases involves pressurizing the greenhouse gases that come from systems that burn fossil fuels in order to liquefy them. These ever-increasing amounts of pressurized liquids would have to be stored in some sort of (underground?) vault indefinitely. The complexity and the cost of such collection/ pressurization/ storage systems defy comprehension. Operating such a system at a scope sufficient to achieve a "carbon-negative world" (in which atmospheric greenhouse gasses cease to increase) would be hard to imagine. Also, the energy costs of pressurization would require additional fossil-fuels combustion.

Another concept involves increasing the inventories of the world's plant biomass (another carbon sink). This biomass would have to consist mainly of trees since this is where the bulk of the world's plant biomass is stored. The problem is that the world is undergoing large-scale deforestation (07S1). A large fraction of the deforestation in developing nations is (1) done illegally, and (2) not recorded in global timber harvesting statistics and (3) virtually impossible to control due to (a) the cost of such controls relative to the financial capabilities of the developing world, (b) systemic corruption in many developing nations and (c) willingness of developed nations and China to receive stolen goods. The world's forests store an estimated 283 gigatonnes (Gt.) of carbon in their biomass alone and 638 Gt. of carbon in the ecosystem as a whole (to a soil depth of 30 cm). So roughly half of total forest carbon is found in forest biomass plus dead wood, and half is in soils plus litter. For the world as a whole, carbon stocks in forest biomass decrease by 1.1 Gt. of carbon annually (05F1). This means that the world's forests are behaving as a source of carbon (greenhouse gasses), a source that is pumping greenhouse gasses into the atmosphere. Even if this carbon source could somehow be turned into a carbon sink, that sink would have a far smaller carbon inventory than the tropical world's soils. This means that the world's forest biomass would need to incur major increases in volume relative to its current biomass inventory to be effective in countering global warming. In today's global forest environment, even becoming a small carbon sink would be a difficult goal to achieve.

Another concept involves large-scale conversion to nuclear power in order to decrease the rate of release of greenhouse gasses into the atmosphere. However, recent Australian studies of global uranium supplies indicate that such supplies are inadequate for large-scale, long-term increases of nuclear power. The potential for expanding the use of breeder reactors (still largely in the experimental stage) has apparently not yet been seriously considered.

A concept that has apparently been considered far less thoroughly than the concepts described above is storage of greenhouse gases in the world's largest organic carbon sink -- soils. The Kyoto meetings on solving the global warming problem do not permit soil storage of greenhouse gasses to be counted as a sink in any nation's calculated contribution to the solution of the global-warming problem. This is possibly because they see such stored organic carbon compounds as mainly temporary, with the largest bulk being "mineralized" into CO₂ and then released back into the atmosphere. In a way this is true. Typical fertile temperate soils tend to stop increasing their organic carbon contents after reaching roughly 3% organic carbon. This permanently stored (stabilized) organic carbon has a half-life in soils of around a century or about 1000 years depending on the chemistry of the storage molecule. The non-stabilized organic carbon is "mineralized" to CO₂ and released back into the atmosphere. Typical tropical soils are able to provide permanent storage (stabilization or "sequestering") only for carbon contents less that roughly 1%. This apparently reflects the fact that "mineralization" is faster relative to the stabilization reaction at higher temperatures typical of the tropics. Lower organic carbon contents imply less fertility.

What the Kyoto meetings are in denial of is the fact that terra preta, in tropical soil environments, is able to provide permanent storage (stabilization) for concentrations of organic carbon much higher than the normal limit of roughly 1% organic carbon in tropical environments. Hence terra preta has the potential of providing a huge sink for the organic carbon that photosynthesis draws from the atmosphere's supply of CO₂. The Kyoto viewpoint is correct in the sense that modern day soil scientists have not yet been able to replicate the ability of the ancient Amazonian indians to create terra preta on a large scale. However that situation is certain to change. Once such a process has been developed, the position of future Kyoto meetings is almost certain to change. Consider:

• The world's total amount of soil organic carbon is about 82% of the global organic carbon in terrestrial ecosystems. This would suggest that soils ought be considered as the first choice in any compilation of strategies for sequestering greenhouse gases.
• Storing carbon in soils can be done in such a way as to draw carbon dioxide from the atmosphere via photosynthesis. (Another greenhouse gas, atmospheric methane, apparently degrades to carbon dioxide in about a decade.) The three strategies described above with non-soil sinks lack this capability.
• Increasing soil organic carbon greatly improves numerous soil properties that are important in agriculture. ((See Section [B5] of Chapter 1 of Ref. (08S1).) Among these properties is increased food productivity. This raises the possibility of (1) reducing or eliminating global warming problems profitably, and (2) reducing or eliminating the developing world's hunger and poverty.
• A process for permanently (half-life of thousands of years) and significantly increasing soil-organic-carbon contents and soil productivities was discovered and developed between 500 and 7000 years ago by Amazonian indian tribes. In fact they developed the process to the point where huge areas of tropical land could be converted to fertile terra preta soils. This apparently resulted in a major advanced civilization in Amazonia- something today's tropical soils are usually incapable of.
• The technology for creating terra preta over large areas has since been lost. However, it is hard to imagine that modern-day soil scientists cannot figure out ways of repeating what ancient indian tribes learned.
• The basic ingredients required for creating terra preta (wood and virtually any organic waste) are readily available and inexpensive, if not free. The key microorganisms involved can apparently be obtained and grown starting from existing terra preta soils (behavior similar to sourdough bread microorganisms.)

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~ [5] ~ Could carbon contents of the world's tropical cropland soils be increased sufficiently to significantly reduce global warming? ~
The total mass of organic carbon stored in soil globally is 1576 Gt. Of this amount, 32% (504 Gt.) is found in tropical soils (93E2). Terra preta has high organic carbon contents of up to 150 grams carbon/ kg. of soil, as compared to normal (low-fertility) tropical soils with 20-30 grams carbon/ kg. of soil (08L1). (Most soil scientists would say 20-30 is abnormally high.) In addition, terra preta soils are carbon-enriched down to 100-200 cm. below the ground surface. Normal low-fertility tropical soils have carbon-enriched depths of 10-20 cm. (Sub-soils typically have very low organic matter contents.) The total amount of carbon stored per unit area of terra preta cropland is therefore about 50 times that in normal, low-fertility tropical soils (08L1). Other sources give factors of 20 (07F3) and 25 (07P1). Taking an average of these three sources gives a factor of 32. Thus, were one to convert all tropical soils to terra preta, the amount of carbon that could be pulled from the atmosphere and provided with permanent storage ("sequestered") in the global soil sink would be 504 x 32 or 16,000 Gt. This is far more than the amount required to eliminate global warming for the foreseeable future. If it is assumed that conversion of tropical soils to terra preta soil is justified only in croplands, i.e. in only about 10% of the world's tropical soils, then the permanent atmospheric carbon removal via photosynthesis and the incorporation of crop residues, human excrements and all manner of other organic wastes (also products of photosynthesis) in permanent storage ("sequestered") would be 1600 Gt. - easily enough to accommodate all current atmospheric carbon (760 Gt.) plus any foreseeable future carbon releases (6.1-9.5 Gt. of CO₂ per year (04O1) (04L1)).

Others have calculated that a strategy combining "bio-char" ("char-wood") production (a key ingredient of terra preta) with bio-fuel production could ultimately offset 9.5 billion tons of carbon emissions per year - an amount equal to the world's total current rate of fossil fuel emissions (04L1). If this strategy were fully utilized, the world would become "carbon-neutral," meaning that the amount of greenhouse gas in the atmosphere would stop increasing. If so, the only greenhouse gas that terra preta would need to remove is some fraction of the current inventory of 760 Gt.

Sequestering huge amounts of carbon for thousands of years would also substantially reduce emissions of methane and nitrous oxide from soils (06C1). Both of these gasses are "greenhouse" gasses. Terra preta also reduces the amount of chemical fertilizers used in tropical soils because "bio-char" ("char-wood") helps to retain nitrogen in the soil as well as plant-available phosphorous, calcium, sulfur and organic matter (06C1). This could reduce nitrate concentrations in surface waters and ground waters. Nitrates in water supplies pose serious human health risks in many parts of the world. They are also instrumental in creating over 400 "dead zones" in the world's oceans. These zones occur mainly in the worst possible places -- estuaries that are normally considered to be key habitats for ocean fisheries. Many nations, particularly the EU, must limit chemical- and organic fertilizer applications in order to keep nitrate concentrations in drinking water below the 50 p.p.m. legal limit required by health considerations. Reducing chemical fertilizer consumption makes the world's food supply much less dependent on energy inputs. This is because natural gas is used as both a feedstock and as a supplier of process heat in the manufacture of chemical fertilizers.

In addition, many bio-fuel production methods (such as generating bio-fuel from agricultural, fish- and forestry- waste) produce "bio-char" as a by-product. As noted above, this process could also withdraw greenhouse gasses from the atmosphere. Lehmann notes that the global importance of a "bio-char" sequestration as a by-product of the conversion of biomass to bio-fuels is difficult to predict. However he contends that it is potentially very large (06C1). However, were the conversion of tropical soils to terra preta be done largely by the world's 200 million or so shifting cultivators as described in Section (6) below, the global significance of off-site "bio-char" production would be far less that what Lehmann currently estimates.

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~ [6] ~ Slash-and-Burn vs. Slash-and-Char ~
In a terra preta-free environment that is the overwhelming bulk of the tropics of today, much of the agriculture is known as "slash-and-burn" or "shifting cultivation." In this process farmers clear small patches of tropical rainforest and then burn the fallen trees to produce various gasses, mainly CO₂, a greenhouse gas, and ash that enriches the soil. The process produces a patch of cropland that farmers use to grow crops. After about three years, the bulk of the soil nutrients and organic matter are "mineralized" to CO₂ or leached into ground waters. This forces farmers to abandon their plots for 10-20 years until tree growth can bring nutrients up from lower soil strata and also provide some organic matter. The "slash-and-burn" process then begins anew. This is probably the same low-productivity agriculture practiced by the ancient Amazonian indian tribes before they discovered and developed terra preta. The number of "slash-and-burn" farm families in the modern-day tropical world is in the hundreds of millions - far more that what all the world's tropical rainforests can support. (For details on the effects of "slash-and-burn" agriculture on tropical forests, see Ref. (07S1)) As a result or this over-population, today's "slash-and-burn" farmers the world over must return to the same plots of land far sooner than the 10-20-year fallow period needed to restore soil fertility. The result is a tragic cycle of decreasing soil fertilities and increasing wretchedness and hunger in the tropics.

All this raises the intriguing question -what if today's "slash-and-burn" farmers were told how to burn the fallen tree trunks, branches, twigs and leaves in an oxygen-poor environment, e.g. by partially covering the wood by soil etc? This is the "slash-and-char" process that produces "bio-char" or "char-wood" instead of the ash that "slash-and-burn" creates. "Slash-and-char" releases about half of the wood's carbon into the atmosphere as greenhouse gasses like CO₂. The other half of the carbon remains in the "char-wood." Lehmann has calculated (03L1) that simply by replacing the usual "slash-and-burn" agriculture by "slash-and-char," up to 12% of the carbon emissions produced by human activity could be eliminated. This replacement produces "char-wood" or "bio-char," a key part of any process for creating terra preta soils that soil scientists ought to be able to come up with. Also this process produces "char-wood" right in the vicinity of where it could be used to create terra preta. This greatly reduces transportation costs relative to processes involving creating both "bio-char" and "bio-fuels" described briefly above. The conversion to "slash-and-char" would be equivalent to eliminating one out of every eight automobiles, planes, busses, trucks, heating systems, fossil-fuel-fired power plants, forest-burning and any other greenhouse-gas-emitting systems on Earth.

Currently "slash-and-burn" farmers would reject the idea of replacing the usual ash by "char-wood" because ash provides soil nutrients and "char-wood" does not - at least to the farmer's current state of knowledge. But what if today's soil scientists could figure out how to use the "char-wood" so created to create terra preta on the "slash-and-char" farmer's plot like the ancient indian tribes probably did in past millennia? The result would be far greater soil productivity and a productivity that would last for thousands of years instead of three years. The farmer could stay in one place, meaning far less labor would be required, and less need for large families to do all that work. Vastly less tropical rainforest would be consumed because new plots of forest would not have to be burned every three years. The farmers' families would be far better fed than ever before. They would have surplus crops to sell in local markets, making them both better-fed and richer. The vast rural-to-urban human migration that is now forcing billions of rural folk to migrate into the wretched slums ringing virtually all the major cities of the developing world would be significantly reduced (08S2). The greater wealth translates into greater knowledge, including knowledge of contraceptives essential to smaller families. Remember that "slash-and-burn" farmers are among the world's poorest people, and the world's poorest regions are the regions that continue to have total fertility rates of 5-7 children per woman. All this should help us all see what is at stake in those current efforts of soil scientists to figure out what those ancient indian tribes somehow managed to learn without any formal education. Actually there is even more at stake than these paragraphs suggest. Section [8] below goes into the remaining issues.

Let's look ahead a bit to try to envision how the world might handle the situation after soil scientists have figured out how to create terra preta in low-fertility tropical soils. The next problem is to figure out how to spread the technology to the bulk of the croplands of the tropical world. This is necessary in order to wipe out global warming and to spread all the other benefits among developing world farmers. The obvious place to start would be the world's several hundred million "slash-and-burn" farmers of the world's tropical rainforests. These people would have both the ability and the resources to create "char-wood." They would also have a huge incentive to learn the new technology, and they are fully capable of learning it because their ancestors of several millennia ago went through the same transformation. Many of them will have access to the terra preta that their ancestors created. This will give them a supply of the key microorganisms that are needed to provide the " sourdough" for growing new terra preta in land that the farmers recently laced with all sorts of organic matter. The "char-wood" apparently stabilizes ("sequesters") this organic matter for thousands of years on the huge internal areas of mineral surfaces that "char-wood" possesses. That organic matter would otherwise be almost entirely "mineralized" and re-enter the atmosphere as CO₂. Word-of-mouth is probably enough to spread terra preta technology throughout the tropical world's "slash-and-burn" farmers of the tropics. From there it would naturally spread to other types of farmers of the tropics. The cost of spreading terra preta technology via this strategy would be minimal. Brazil would become one of the world's richest (and most powerful?) nations, particularly since they have an active family planning program and have achieved a fairly low rate of population growth. (This reduces the huge drain on financial capital that population-growth-driven infrastructure expansion represents.) This incentive is probably sufficient to persuade Brazil to fund dissemination of terra preta technology. Illegal logging on its current huge scale could pose serious risks to this rosy vision of Brazil's future however.

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~ [7] ~ The Effects of "Slash-and-Char" on Tropical Rainforests ~
Admittedly the effects of replacing "slash-and-burn" agriculture by "slash-and-char" terra preta-based agriculture on tropical rain forests are not clearly established. This is because the process of large-scale creation of terra preta is not yet known. More specifically, we do not know how much "char-wood" a given area of terra preta will require. However the possibilities look intriguing. For example, let us assume that a "slash-and-char" farmer can produce enough "char-wood" from an acre of tropical forest to satisfy the needs of an acre of terra preta. In that case, the farmer is set for life. Instead of burning additional patches of tropical rainforest every three years or so for the rest of his/her life, he/she burns only one patch. In that case, huge reductions in tropical rainforest burning could be expected. Even if it took six or so acres of tropical rainforest to satisfy the "char-wood" needs of an acre of terra preta, reductions of tropical rainforest destruction would still be significant. Don't forget that the half-life of "char-wood" in terra preta is probably in excess of 5000 years (assuming it to have the same half-life as charcoal). So once a farmer's patch of terra preta has its supply of "char-wood" there is no further need for further additions, and hence no further need to burn more tropical rainforest. The carrying capacity of tropical rainforests under "slash-and-burn" agriculture is widely known to be about 10 people per square kilometer (84G1). On the other hand, widespread use of terra preta in Amazonia is reputed to have spawned a great civilization in millennia long past - something that "slash-and-burn" agriculture could not possibly support, then or now.

~ [8] ~ Potential side effects of large-scale conversions to terra preta ~
Low-fertility soils are largely seen as the main reason why developing nations are located in the tropics (or in regions where the soils, forests, grazing lands and irrigation systems have been degraded by millennia of abuse by ancient civilizations). The possibility of large-scale terra preta agriculture suggests the possibility of developing nations evolving economically into developed nations as a result of significantly increased soil organic matter sequestered in tropical soils. This is not certain however. During the past 100 years, only about eight nations were able to make the transition from developing world status to, or nearly to, developed world status. All these transitions were made during periods when those eight nations were carrying on active family planning programs that resulted in reductions of total fertilities to 2.3 or less (97P1). Nations with high population growth rates tend to suffer from extreme shortages of financial capital as a result of the demands for the infrastructure growth needed to accommodate population growth. The developing world as a whole with a population growth rate of 1.3%/ year needs $1.4 trillion/ year in infrastructure expansion called for by population growth. Nations with median earnings of less than $2/ person/ day do not have this kind of money. So we see such things as sub-Saharan Africa having such poor transportation infrastructure that imported chemical fertilizer costs 60 times as much as in the EU on a pounds-of-fertilizer-per-hour-of-labor basis. The soil is being mined of its nutrients, and hunger and armed conflicts (04P1) are some outcomes.

Perhaps the main reason why large-scale conversions to terra preta soils could fail is that a critical ingredient is "char-wood" ("bio-char") (wood and/or other organic matter burned in an oxygen-poor environment). A possible result of increasing tropical world food productivities could be increasing population growth rates in developing nations, although the opposite could happen, as noted in the previous section. Even if that did not occur, deforestation (even at present-day rates) could reduce the supplies of wood essential for conversion to "char-wood" to levels that could be insufficient for large-scale creation to terra preta. However, much of the deforestation is a result of "slash-and-burn" agriculture. If that agriculture could be converted to "slash-and-char" agriculture and terra preta agriculture, tropical deforestation rates could be greatly diminished. The risks of a scarcity of "char-wood" might be less that one might estimate because "char-wood" creation would need only branches and limbs of trees. Loggers usually discard such types of biomass. Large-scale conversion to terra preta would require a careful balance between the inventories of tropical cropland, forestland and wood. Details of this balance must await a better understanding of the wood requirements per unit area of terra preta soils. The wood supply problem might also not be as big a problem as one might surmise because, once a given area of cropland is converted to terra preta soils, no further char-wood is required to perpetuate such soils. So subsequent generations of trees could serve to extend the range of terra preta soils. In Appendix I are some data that provide insights into the scale and context of illegal logging in developing nations.

Still, the growth of human populations during the first half of the 21^st century is expected to be 60% in the developing world. So it is hard to feel safe in surmising that the risks of massive deforestation by 2050 (or long before) are minimal. It would be foolhardy to believe that terra preta could enable developing nations to avoid the active family-planning programs that provided such huge benefits to the nations that moved from developing world status to developed world status during the past 100 year.

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~ [9] ~ The Possibility of Producing an Ice Age ~
The terra preta strategy for dealing with global warming offers a major benefit relative to other strategies in addition to simplicity, low cost, and political viability. It can draw greenhouse gasses already in the atmosphere back out of the atmosphere via the process of photosynthesis. However this advantage comes with a potential harmful side effect. It could, in theory, produce an ice age. It would seem important, then, that we consider under what conditions this might happen. If terra preta was created only for food production, increasing tropical soil productivities by a factor of 2-3 would create a glut of food, and food prices would reflect this and there would be little risks of an ice age. However several estimates of Africa's unmet needs for food and its high population growth rate gives a need for tripling Africa's food production, so this might create problems. There are other scenarios. Sugar cane is the best starting material for creation of bio-fuels, and growing global energy needs in an environment of diminishing fossil fuel reserves could result in vast additional tropical lands being converted to terra preta soils for growing sugar cane for bio-fuels. Also, the conversion of grazing land soils to terra preta might be found to be economically viable. If so, the carbon-sequestering capacity of tropical soils could become far larger than estimated here. Either of these two scenarios would significantly increase the risk of an ice age.

Were atmospheric concentrations of CO₂ to fall significantly, the rate of photosynthesis would decrease worldwide, although by amounts significantly less that direct proportionality. This could reduce the rate of sequestering of organic matter in the world's soils. The problem in all this is that we don't yet know what soil scientists will come up as a recipe for creating terra preta soils. We also do not know how thick the terra preta will be. It will certainly be at least as thick as typical plant root zones will be (6-10"), although if terra preta is used to increase the productivity of fruit trees, root zones will be several times that. Clearly there are too many unknowns at this point to produce reliable estimates of the risks of another ice age, although there are obviously risky scenarios that should be kept in mind. Only after terra preta science and technology become better understood would the degree of speculation on this risk be reduced to acceptable levels. In addition, we do not know much about the kinetics of the ice age development process. If greenhouse gas levels were reduced to well below pre-industrial levels, hundreds or thousands of years might be required before global mean surface temperatures drop to ice-age levels.

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~ [10] ~ Conclusions ~
It is long past time for a realistic assessment of the likelihood of anything being done on a global scale in response to the clear and obvious threat of global warming. Kyoto meetings every decade or so show no signs of accomplishing anything beyond token gestures, the effects of which are easily overwhelmed by the effects of population growth and economic growth. Even such powerful proponents of addressing global warming as Germany backed out of its commitment in mid-2008 (08B1). Every proposal so far for addressing global warming involves massive complexity and expense or is incapable, physically, of working. Also, they all only slow the rate of greenhouse gas introduction into the atmosphere. None have the ability to reduce the concentrations of greenhouse gassed already in the atmosphere -concentrations already sufficient to melt Greenland's ice cover and produce a 25-meter increase in sea levels by the turn of the century (08H1). Just a few of the numerous possible consequences suggest that few of the earth's inhabitants will escape these consequences. Glacier melting threatens the continuity of water flows to half the people on the planet, and hence the viability of about the same fraction of the world's irrigation systems (source of 70% of the world's food supplies). Bangladesh will cease to exist, and its 150 million people will need to move elsewhere. India is already building fences along its boundary in preparation. The effects on the world's oceans thus far are producing devastating effects on Bangladesh's crops, water supplies, and other essentials. Bangladesh's other neighbor, Burma, could not even begin to accommodate such seas of humanity (08H1).

With that backdrop in mind, consider now what should be concluded to be the only physically workable, economically viable, and politically feasible strategy for dealing effectively with global warming -and the only strategy capable of reversing (not just slowing) the flows of greenhouse gasses into the atmosphere. That strategy is also simple, and it has numerous major beneficial side effects. That strategy is:

• Invest an additional few tens of millions of dollars into the research efforts of the dozens of soil scientists from around the world now involved in the terra preta issue. These funds should be expected to speed up the process of relearning what primitive indians learned thousands of years ago. There is no reason for believing that such efforts might ultimately fail. Success is clearly just a matter of time.
• Instruct widely scattered groups of the 200 or so million "slash-and-burn" tropical farmers of what the soil scientists learned. This should be simple, given the huge incentives for such farmers to learn the skills of their ancestors - major increases in crop productivity plus major reductions in the amount of agricultural labor required (e.g. no more need to move to a new plot of ground every three or so years and to clear the tropical forest from it). "Slash-and-char" farmers would be able to reside on the same plot of ground all their lives. Information flow via word-of-mouth under such circumstances should be rapid, and make its way to all the the non-slash-and-burn farmers of the tropics.

It's as simple as that.

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Appendix I ~ Illegal Logging in Developing Nations - Some insights:

Ref. (06F1) includes estimates of illegal logging rates as a percentage of total production in 17 countries, from Bolivia to Myanmar and Vietnam. At least 2/3 of those 17 countries have illegal logging rates of at least 50%. In Indonesia, 70-80% of all logging was illegal. All told, illegal logging alone has eliminated 100,000 km² of Indonesia's forest cover (02F1). In Bolivia 80% of timber harvests were illegal. In Cambodia it was estimated at 90% (06F1). The illegal timber trade in the Philippines may be 4 times the size of the legal trade, suggesting that 80% of timber harvests are illegal (Ref. 61 of Ref. (93D2)). Estimates suggest up to 80% of logging is illegal in the Brazilian Amazon and 73% of logging is illegal in Indonesia (02F1).

The World Bank believes the illicit global trade in timber costs governments (worldwide) about $15 billion/ year in lost revenues and taxes (07W1) (03U2). FOE (Friends of the Earth) has concluded that 50% of all timber entering the EU may be illegally sourced, and in the UK the rate is 60% (02F1). China does not currently distinguish between legally and illegally produced timber imports (06F1). The World Bank, the International Monetary Fund, Japan, the EU, France, Germany, Britain and the US, fail to enforce their own rules designed to promote forest conservation and responsible timber management. Then they induce developing nations to sell their forests for a quick cash return to pay off debts to Western countries (The Guardian (UK) (6/1/00)). In a study of 120 countries, "high deforestation" countries (those that lost 10+% of their forest cover during 1980-85 -- 20 countries including Haiti, Iraq, Nicaragua, South Africa, and Sri Lanka) are 3 times more likely to be governed by a military leader, 4 times more likely to experience political assassinations, and two times more likely to witness general strikes, riots, revolutions and changes in government (94U1). Ref. (94D1) cites numerous examples of the influence of political corruption on global deforestation.

84G1 Nicholas Guppy, "Tropical Deforestation: A Global View", Foreign Affairs (Spring 1984) 62, pp. 928-965.

93D2 Alan Thein Durning, "Saving the Forests: What Will it Take?" World Watch Paper 117 (December 1993) 51 pp.
93E2 H. Eswaran, E. van Berg, P. Reich, "Organic carbon in soils of the world," Journal of the Soil Science Society of America 57 (1993) pp. 192-194.

94D1 Alan Thein Durning, "Redesigning the Forest Economy", in Linda Starke, editor, State of the World 1994, W.W. Norton and Co., New York (1994) pp. 22-40.
94T1 H. Tiessen, E. Cuevas and P. Chacon, "The role of soil organic matter in maintaining soil fertility," Nature 371 (1994) pp. 783-785.
94U1 (Unknown), "Can't See the Forest for the Politics", Environment, 36(9) (1994) p. 21.

97P1 David Poindexter, "Population Realities and Economic Growth," Population Press, 4(2) (Nov/ December 1997) http://www.popco.org/irc/essays/essay-poindexter.html.

99W1 W. I. Woods, J. M. McCann, "The anthropogenic origin and persistence of Amazonian dark earths," Yearbook, Conference of Latin Americanist geographers 25 (1999) pp. 7-14.

02F1 Friends of the Earth, "Why the Earth Summit Matters", Guardian UK (5/19/02)).

03L1 Johnnes Lehmann et al, editors, Amazonian Dark Earths: Origin, Properties, Management Kluwer Academic Publishers, Dordrecht, Netherlands (2003).
03S1 Wm. G. Sombroek et al, "Amazonian Dark Earths as Carbon Stores and Sinks," in Johnnes Lehmann et al, editors, Amazonian Dark Earths: Origin, Properties, Management Kluwer Academic Publishers, Dordrecht, Netherlands, pp.125-139.
03U2 (Unknown) "Forest Cover Shrinking: Forests Provide Annual Wood and Services of $4.7 Trillion Worldwide", Earth Policy Institute, 1/3/03 www.earth-policy.org/Indicators/indicator4.htm.

04D1 William M. Denevan, William I. Woods, "Discovery and Awareness of Anthropogenic Amazonian Dark Earths (Terra Preta) (2004) http://www.georgiaitp.org/carbon/PDF%20Files/Bdenevan.pdf (visited 8/29/08).
04L1 Johannes Lehman et al, Amazonian Dark Earths: Origin, Properties, Management, Springer (1/31/04) 523 pp.
04O1 M. Obersteiner (2004) Retrieved from http://www.eprida.com/hydro/ecoss/presentations/symposiums.htm
04P1 Population Action International, "How Demographic Transition Reduces Countries' Vulnerability to Civil Conflict" in PAI's publication The Security Demographic: Population and Civil Conflict After the Cold War, (2/11/04) http://www.populationaction.org/resources/factsheets/factsheet_23_securityDemog.html.

05F1 FAO (Food and Agriculture Organization), Global Forest Resources Assessment 2005, FRA Forestry Paper 147 (2005) http://www.fao.org/forestry/site/fra/en The entire report can be downloaded as a .pdf file (6 MB) Key findings can be downloaded as a .pdf report (1.43 MB). Individual chapters and appendices (annexes) can also be downloaded.

06B1 Biopact Team, "Terra Preta: how biofuels can become carbon-negative and save the planet," Biopact (8/18/06) http://biopact.com/2006/08/terra-preta-how-biofuels-can-become_18.html
06C1 Cornell University, "Amazonian Terra Preta Can Transform Poor Soil Into Fertile, Science Daily (3/1/06) Retrieved 8/25/08 from http://www.sciencedaily.com/releases/2006/03/060301090431.htm
06F1 David Fogarty, "Illegal logging costing nations billions - World Bank," Reuters AlertNet (9/16/06)
06G1 Bruno Glaser, "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century," Philosophical Transactions of the Royal Society B 362 (2006) pp.187-196.

07E1 Richard Embleton, "Terra Preta Soils - Agricultural Miracle from the Past?" Oil, be Seeing You (6/27/07) http://www.oilbeseeingyou.blogspot.com/2007/06/terra-preta-soils-agricultural-miracle.html (visited 8/25/08).
07F3 Jeremy Faludi, "A Carbon-Negative Fuel," World Changing (10/16/07).
07P1 Philip Proefrock, "Terra Preta for Carbon Reduction," Energy (10/17/07).
07S1 Bruce Sundquist Forest Land Degradation - A Global Perspective, Edition 6 (July 2007) http://home.alltel.net/bsundquist1/df0.html
07S2 Bruce Sundquist Topsoil Loss and Degradation - Causes, Effects, and Implications: A Global Perspective, Edition 7 (July 2007) http://home.alltel.net/bsundquist1/se0.html
07S3 Bruce Sundquist Grazing Lands Degradation - A Global Perspective, Edition 6 (July 2007) http://home.alltel.net/bsundquist1/og0.html
07S4 Bruce Sundquist Irrigated Lands Degradation - A Global Perspective, Edition 5 (July 2007)) http://home.alltel.net/bsundquist1/ir0.html
07S5 Bruce Sundquist Fishery Degradation - A Global Perspective, Edition 8 (July 2007) http://home.alltel.net/bsundquist1/fi0.html
07W1 Tom Wright, "Timber Smuggling Tests Indonesia," Wall Street Journal (7/3/07) p. A4.

08B1 Chris Bryant et al, "Climate change fears after German opt-out," Financial Times (9/22/08).
08H1 Johann Hari, "Bangladesh is set to disappear under the waves by the end of the century," New York Times (6/20/08)
08L1 Johannes Lehmann, "Terra Preta de Indio," Soil Biogeochemistry (2008) http://www.css.cornell.edu/faculty/Lehman/terra_preta/terraPretahome.htm (visited 8/29/08).
08R1 Ed Ring, ECOworld (11/27/08) http://ecoworld.com/blog/2007/11/27/terra-preta/
08S1 Bruce Sundquist Sustainability of the World's Outputs of Food, Wood and Freshwater for Human Consumption Edition 1 (March 2008) http://home.alltel.net/bsundquist1/su0.html
08S2 Bruce Sundquist The Informal Economy of the Developing World: The Context, The Prognosis, and a Broader Perspective, Edition 1 (March 2008) http://home.alltel.net/bsundquist1/ie.html
08S3 Swedish University of Agricultural Sciences, "Limits of Charcoal As An Effective Carbon Sink," Science Daily (5/4/08).
08S4 Bruce Sundquist The Controversy over U.S. Support for International Family Planning - An Analysis, Edition 8 (April 2008) http://home.alltel.net/bsundquist1/ifp.html 

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