TERRA PRETA -- AN INEXPENSIVE, IF NOT PROFITABLE, SOLUTION TO THE PROBLEMS OF GLOBAL WARMING AND DEVELOPING WORLD HUNGER

Edition 5 - February 2009
by
Bruce Sundquist
bsundquist1@windstream.net

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~ Table of Contents ~
~ Abstract ~
~ [1] ~ Modern History and Potential Benefits of Terra Preta Technology ~
~ [2] ~ Some Essential Soil Chemistry Basics ~
~ [3] ~ Likely History and Characteristics of Ancient Patches of Terra Preta ~
~ [4] ~ What is Required for Terra Preta to Eliminate the "Big Ticket" Costs of Global Warming? ~
~ [5] ~ Could carbon contents of the world's tropical cropland soils be increased sufficiently to reverse global warming? ~
~ [5A] ~ Is the carbon sink represented by the conversion of tropical cropland soils to terra preta soil large enough to hold the amount of carbon that must be drawn from the atmosphere in order to reverse global warming? ~
~ [5B] ~ Is it reasonably possible for biochar and organic matter to be added to tropical soils at a rate sufficient to exceed the rate of growth of atmospheric carbon? ~
~ [ 6] ~ Slash-and-Burn vs. Slash-and-Char ~
~ [ 7] ~ Effects of Slash-and-Char on Tropical Forests ~
~ [ 8] ~ Potential Side Effects of Large-Scale Conversions to Terra Preta ~
~ [ 9] ~ The Possibility of Producing Excessively Low Global Mean Surface Temperatures ~
~ [10] ~ Kyoto Views toward the Terra Preta Strategy ~
~ [11] ~ Terra Preta' Competitors: A Comparison of Alternatives ~
~ [12] ~ Conclusions ~
~ Appendix I ~ Illegal Logging in Developing Countries: Some Insights ~
~ References ~

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Previous Editions: 1 (Sept. 2008), 2 (Nov. 2008), 3 (Dec. 2008), 4 (Jan. 2009)

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.

  Abstract ~
The fundamental problem with most tropical soils is their low organic matter contents, and hence low fertilities, 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. Amazonians discovered the solution to this problem at least 7000 years ago, and then spread their technology to 1-10% of Amazonia. This is the only known instance in all of human history in which humans have permanently and beneficially changed soil fertilities over a significant area. The technology was never transferred to European immigrants to the new world. Patches of ancient fertile tropical soils were discovered in Brazil around 1870, but did not attract international scientific attention until around 2001. As a result, soil scientists from around the world now work to discover how to replicate the still-fertile ancient soils ("Terra Preta") that Brazilians extract and sell. Success seems certain, given the scientific capabilities of modern-day soil scientists relative to those of ancient Amazonians. Success would 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. Converting tropical cropland soils to terra preta would also reduce, or eliminate, the need for shifting cultivators to abandon their cropland every three or so years and clear new patches of tropical forest.

Success would also create an additional carbon sink large enough to hold all current and future anthropogenic greenhouse gas emissions out to around the year 2100. Photosynthesis would draw atmospheric greenhouse gasses into tropical vegetation. Tropical farmers would incorporate such vegetation plus "biochar" into their cropland soils to create terra preta where there the half-life of such organic matter and "biochar" would be increased to over 5000 years as compared to the normal half-life of 3-30 years. The result would be a large carbon sink. Farmers would be rewarded for their efforts by a doubling or tripling of their soil's fertility. The net cost of the sink to mankind would be virtually zero. This sink could restore global mean surface temperature to that prior to start of melting of the Greenland ice cap and prior to the shrinking of the bulk of the world's glaciers. This would largely eliminate the two "big ticket costs" of global warming.

An examination of the five main alternative strategies for addressing global warming finds that even the combined results of all five strategies could not, realistically, eliminate the "big ticket costs." Even worse, aside from the terra preta alternative, only one other alternative, the forest biomass alternative, is even theoretically capable of eliminating the "big ticket costs" of global warming. That alternative comes with an impossibly large cost and four serious risk factors that virtually insure failure. It seems safe to conclude that there is only one or fewer viable alternatives for addressing global warming. The terra preta alternative is that one. By a stroke of good fortune, that alternative comes with the lowest price tag, the least risk, and the most beneficial side-effects of all the known alternatives for addressing global warming.

~ Context ~
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 that field. The science 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). This author also makes no claim to being the originator of a possible link between terra preta and global warming. Soil scientists have been suggesting, for at least the past 6-7 years, that terra preta might be used to reduce or eliminate global warming. This document merely contributes the following to that issue:

The inherently low fertilities of tropical soils, relative to temperate soils, largely explain the geography of the divide between the developing world and the developed world. One should not be surprised, then, when studies of possible ways of increasing tropical soil fertilities lead to several substantial effects on the future evolution of human cultures. This document points out several of these possible effects.

~ [1] ~ Modern History and Potential Benefits of Terra Preta Technology ~
The first published mention of fertile "dark earth" in Amazonia was in 1870 by James Orton of Vassar (04D1). In the last quarter of the 20th century the discovery precipitated occasional scientific papers mainly related to the curiosity value of the discovery. However the significance of terra preta (Portuguese for "dark earth") in Amazonia did not achieve international awareness until 2001-2002 (04D1). It was probably around then that scientists realized the potential of this ancient technology in terms of:

As a result, scientists from many parts of the world are now trying to reproduce the technology, including the ability to spread the technology for creating these fertile tropical soils over large areas. An organization has been formed to coordinate the research of scientists working to better understand terra preta science and to improve on terra preta technology.

The discoveries of 1870 also re-ignited interest in ancient reports by Spanish explorers. These reports alluded to the "golden" cities of El Dorado in Amazonia. These reports tended to be discounted by the argument that Amazonia's soils could not support such advanced civilizations. The 1870 discovery eliminated this argument. The "golden" part of the reports was almost certainly false. However later reports contended that the impact of European diseases on Native Americans in the region was far greater that previously conjectured. These later reports suggested that these diseases destroyed a network of complex urban civilizations with a total population of over 100 million. These may have been the urban civilizations that the early Spanish explorers referred to as "El Dorado." Such civilizations would have required soils more fertile that typical tropical soils - such as terra preta.

Success on the part of these modern-day soil scientists seems assured, since one can hardly imagine such scientists being unable to accomplish what ancient Amazonians were able to accomplish. It appears that among the first outcomes of this success could be the elimination of global warming. This would be a result of the improved tropical soils creating a carbon sink capable (via photosynthesis) of capturing and sequestering the past, current and future anthropogenic releases of greenhouse gasses for many decades. This would suggest that the elimination of global warming via sequestering of greenhouse gasses in tropical soils could be accomplished at low cost. Section [11] below examines the other strategies for addressing global warming and finds that even utilizing all of them together could not realistically reduce global mean surface temperatures. Soil sequestration of carbon in the terra preta of tropical croplands makes negative net carbon release rates, and hence a falling global mean surface temperature, possible.

Another likely outcome of success on the part of modern soil scientists is major economic benefits to developing nations in the form of significant increases in tropical soil fertilities that could produce major reductions in human hunger. The benefits to tropical farmers could compensate these farmers for converting their cropland soils to terra preta. This would make the net cost of creating a huge cropland soil sink for carbon small or negative. Whether soil fertilities as far north as the southern US could be enhanced by terra preta technology has apparently not yet been determined. An experiment in Sweden suggests that it might not be (08S3).

Yet a third possible outcome of success is reductions in tropical forest deforestation where most of the world's deforestation takes place. (The IPCC [Intergovernmental Panel on Climate Change] estimates that 10-30% of the increase in carbon dioxide emissions is due to land-use changes, particularly deforestation (01P1).)

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~ [2] ~ Some Essential 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), soil fertilities degrade to a small fraction of what they were as closed systems. As a result, garden plots of tropical shifting cultivators (also referred to as "slash-and-burn" agriculture) 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 low fertilities after 7-10 years of grazing. 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. Some tropical soil types cannot support anything but the most simple civilizations. 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, and many more are malnourished.

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 (held in place by) soil organic matter. So, with less soil organic matter, these key nutrients tend to leach out into the surface waters and ground waters that drain 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 (typically originating as soil surface litter) with soil minerals, e.g. clay, to form organo-mineral complexes (sometimes chelates) that are stable and long-lasting (half-lives of between 100 and 1000 years depending on the chemical composition of the complex and other factors). Compare these half-lives to the 3-10 year half-lives of soil organic matter not bonded to soil minerals. The other chemical reaction is the "mineralization" of soil organic matter (also called "decomposition"). This typically involves combining soil carbon chemically with oxygen or hydrogen to form CO2 or CH4 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. In wetlands, peat bogs, rice fields and landfills, oxygen is in short supply. Thus mineralization (decomposition) rates are slower, resulting in high carbon contents and the typically black color of soils in these environments, including some lake bottoms where you can find logs that are over 1000 years old. Some mineralization does occur in these environments, but the product is often methane (CH4) that, like CO2, escapes into the atmosphere, depletes soil organic matter, and is a greenhouse gas. In the atmosphere, methane decays to CO2 in 7-10 years.

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 detracts from soil fertility since the reaction products leave the soil and go into the air, surface waters, or ground waters, depleting the organic matter contents of the soil. 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 a large part of why organic carbon contents in temperate soils (about 3%) are higher than in tropical soils (about 1%) - 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 played major roles in determining the course of human history.

This picture of soil development is overly simplistic. Some tropical soils, particularly in Africa, are described as "old" and "weathered." Many are quite sandy. Opportunities for forming organo-mineral complexes are therefore far fewer. The result is lower organic matter contents and lower fertilities. Other ignored complexity result form the fact that organic matter mineralizes at different rates depending on their chemistry, soil moisture, variations in soil microorganisms, what soil minerals the organic matter becomes bonded to, and the extent of aggregation of the organic matter (96P1). High levels of soil moisture can reduce oxygen availability and, as a result, produce soils with almost 100% organic matter (e.g. peat).

Chemical fertilizers add even greater complexity. When one applies chemical fertilizers to tropical soils, the nitrogen, phosphorous and potassium have less organic matter to attach to and are therefore leached at a higher rate into the groundwater. Temperate soils, with their higher organic matter contents, can better hold the nutrients contained in chemical fertilizers and are therefore less prone to leaching of these nutrients. Yet, some nutrients from chemical fertilizers do leach out of temperate soils. Adding excessive amounts of chemical fertilizers can produce human health problems as a result of nitrate buildups in water supplies. Problems with fisheries also result as a result of excess nutrients creating "dead-zones" in estuaries. Estuaries are usually among the most fertile regions for fisheries in the world's oceans. Unfortunately, dead zones, globally, now number 405 (08B2).

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. 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. It turns out that achieving high soil organic matter contents in tropical soils, and maintaining them indefinitely, is far from impossible as will be seen below.

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~ [3] ~ Likely History and Characteristics of Ancient Patches of Terra Preta ~
About 7000 years ago (06G1) people in Amazonia (the Amazon River basin - now essentially most of Brazil) apparently stumbled on a way of increasing soil organic matter contents, perhaps by noting the higher fertilities (and longer durations of this fertility) of the soils below their campfires. Realizing the implications of their discovery to their own lives, they apparently proceeded to perfect the process and spread the knowledge of the process throughout 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). One should avoid under-estimating the talents of the pre-Columbian indians of what is now South and Central America. They developed corn by a breeding process so sophisticated that the journal Science described it as "man's first, and perhaps greatest, feat of genetic engineering (05M1). They are also believed to have developed the modern peach palm by hybridizing palms from several areas, including the Peruvian Amazon at least 2,300 years ago (05M1).

Throughout Amazonia one finds countless patches, roughly 50 acres (0.2 km2) in size, of fertile soil with depths of up to about two meters (04D1). Patches of up to 5 km2 in area 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, probably because these nutrients attach to the abundant soil organic matter instead of being leached into the ground water -their usual fate in low-fertility tropical 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 (07F3) and 25 (07P1).) 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 was found to be that tropical rains do not leach nutrients from 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.

Making use of the benefits of terra preta requires a way of converting low-fertility tropical soils into terra preta on a large scale like ancient Amazonians apparently did (e.g. patches with an area of 5 km2). 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 reductions, reduced deforestation rates, 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.)

It has become apparent that soil microorganisms play an important, but poorly understood, role. When Amazonians 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, and spreading terra preta technology over large portions of Amazonia. Recent experiments suggest that the role of soil microorganisms may not be all that critical to the behavior of terra preta, and that the creation of terra preta may be easier than some believe. Soil scientists at the Brazilian Agricultural Research Enterprise and the University of Bayreuth (Germany?) created a simple version of terra preta without any attempt to re-create the ancient microbial balance. By the second year, fertilities of the simple version of terra preta had increased by as much as 880% (05M1).

Possibly the most important hint as to just how terra preta increases soil fertilities, and sustains these fertilities over thousands of years, is that it contains large amounts of charred wood ("biochar") 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 "biochar" were found to 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 "biochar" would have a much shorter half-life. (Experiments at the Kansai Environmental Engineering Center near Kyoto Japan demonstrated that "biochar" retains its carbon in the soil for up to 50,000 years (05M1).) Food scraps, bones of small animals, human excrement, livestock manure, tree components and assorted other types of organic matter were mixed with the "biochar" by ancient Amazonians. The "biochar" buried in the soil probably came initially from cooking fires. (Some of the firewood there would be burned in an oxygen-poor environment, producing "biochar" rather than being converted entirely to CO2 and ash.) biochar is very porous, and the 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 "biochar" would have much less.) Apparently these huge amounts of surface area provide sites for the formation of organo-mineral complexes discussed in Section [2]. These complexes apparently keep soil organic matter and the nutrients in it from being "mineralized" (e.g. converted to CO2) or leached into groundwaters.

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~ [4] ~ What is Required for Terra Preta to Eliminate the "Big Ticket Costs" of Global Warming? ~
First, we need to define the term "big ticket costs." The earth's global mean surface temperature is already high enough to melt the Greenland ice cap and the world's 10,000 glaciers. The ice cap melting problem threatens to submerge vast coastal areas worldwide, including large urban areas and even countries like Bangladesh with a population of 150 million. The glacier problem threaten the continuity of flow of water to about half of the world's population, and to about half of the world's irrigation systems, i.e. about 30% of the world's food supply. These costs are what are referred to throughout this document as the "big ticket costs." Obviously only a process capable of extracting greenhouse gasses from the atmosphere and sequestering the associated carbon indefinitely can avert these costs. This requirement eliminates all but two of the known alternatives for addressing global warming. (See Section [11].)

The earth's atmosphere contained 383 parts per million (ppm) 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.). About 185 Gt. of this 760 Gt. of carbon would have to be removed if the concentration of greenhouse gasses in the earth's atmosphere is to be reduced to pre-industrial values (02M1) (01P2). Without the remaining 575 Gt. of carbon in the form of greenhouse gases surrounding the earth, the earth's surface would be about 33 C (59o F) colder (global average temperature 0o F vs. the current 59o F), so the natural greenhouse effect is essential for life on earth (02M1). The amount of CO2 in the global atmosphere increased, during 2004-2008 at a rate of 0.52%/ year (00P1) (08U1) (i.e. at a rate of 3.8 Gt. C/ year (0.0052 x 760 Gt. C/ year). This rate is apparently the net result of:

Any successful strategy for fighting global warming must create a "carbon-negative" world. To do this, it must remove at least 3.8 Gt. C/ year from the atmosphere. In addition, to reduce the global mean surface temperature low enough to halt the shrinkage of the world's 10,000 glaciers and to halt the net loss of ice from Greenland's ice cap, it must remove some fraction of the 185 Gt. of surplus atmospheric carbon that have been introduced since the start of the industrial revolution. Since the shrinkage of the world's glaciers and the net melting of Greenland's ice cap have been on-going for well under the time span of the industrial age, the assumption is made here that removing only 100 of the 185 Gt. C would be sufficient to halt these two melting processes. This requires some sort of terrestrial sink capable of gathering carbon (mainly in the form of CO2) from the atmosphere and storing that carbon permanently. Soil is the most obvious sink since the global inventory of soil organic carbon is about 82% of the global organic carbon in terrestrial ecosystems. The only other possible sink for carbon capable of extracting greenhouse gasses from the atmosphere is a forest devoted exclusively to sequestering carbon in its biomass. As will be seen in Section [11] below, such a sink entails four huge risks and an extremely high price tag, making the forest biomass option virtually impossible. No other sink is known (other than the terra preta sink) to be able to extract greenhouse gasses from the atmosphere and thus be able to eliminate the "big ticket" costs of global warming.

The two goals mentioned above are essential to:

These are probably the most serious and costly consequences of global warming, so they are referred to in this document as the "big-ticket" costs of global warming.

In non-terra preta tropical soils with an organic carbon content of, say, 1%, the various products of recent and long-past photosynthesis (crop residues, tree roots, soil surface litter and other forms of organic matter that get naturally incorporated into the soil, plus organic matter such as human excrements, livestock manure, food wastes, dead animals, tree foliage, and various other carbon-containing (organic) wastes that humans deliberately bury in the soil) are all essentially mineralized back into the atmosphere as CO2 over a time frame of roughly 3-10 years, since we know that the carbon content of non-preta soils remains at a constant 1%. Terra preta soils offer the unique advantage of enabling some or all of the above-mentioned products of photosynthesis to get chemically bonded (apparently) to sites on the extensive surfaces of "biochar." This reaction stabilizes organic matter indefinitely (thousands of years) so they are not mineralized back into the atmosphere that they came from. This, in essence, is how terra preta becomes a sink for carbon. This sequestering increases tropical soil fertilities and reduces the content of greenhouse gasses in the earth's atmosphere.

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~ [5] ~ Could carbon contents of the world's tropical cropland soils be increased sufficiently to reverse global warming? ~
This question has two parts. The answer to both parts must be in the affirmative for the above question to also be also answered in the affirmative. The two parts of the above question are addressed in Sections [5A] and [5B] below.

~ [5A] ~ Is the carbon sink created by the conversion of tropical cropland soils to terra preta soil large enough to hold the amount of carbon that must be drawn from the atmosphere in order to reverse 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). Our first task is to estimate how much of the 504 Gt. stored in tropical soils is found in the croplands of the tropical world. It seems reasonable to assume that soil organic carbon is distributed uniformly about the world's tropical soils. Then our problem reduces to one of estimating the fraction of the tropical land area that is cropland. Three categories of tropical croplands need to be considered. Irrigated croplands should be neglected because their soils are already quite carbon-rich as a result of being in a low-oxygen environment (much like virtually any wetlands). Data are available for total cropland areas and irrigated cropland areas on a country-by-country basis (00U1). Data on the total area of each country are also available (91W1). Here we neglect China, India and Bangladesh because not all of the cropland there is tropical, and rather extreme deforestation would make it virtually impossible to convert any of the tropical croplands in these countries into terra preta for lack of "biochar." Data are lacking on the total area of cropland being cropped by shifting cultivators. (Published data on cropland area apparently omit cropland under shifting cultivation.) However we know that the total area of forests in tropical climates is 24.5 million km2 (See Ref. (07S2) Ch.[3] Sect.[C].) We also know that, ordinarily, shifting cultivators use (or should use) a cycle of three years of cropping followed by about 20 years of fallow. We also know that there are more shifting cultivators in tropical forests than can be sustained. (See Ref. (97S1) Ch.[4] Sect.[4-A-b].) This enables us to at least compute a minimum area of croplands under shifting cultivation in tropical forests of 13% of forest area, i.e. 3.195 million km2. Adding this to the area of non-irrigated croplands in tropical climates (3.69 million km2) gives a total tropical cropland area of 6.89 million km2. This is 14.7% of the total land area (46.87 million km2) with tropical climates.

Terra preta has high organic carbon contents of up to 150 grams of organic carbon/ kg. of soil (15%), as compared to normal (low-fertility) tropical soils with 20-30 grams organic carbon/ kg. of soil (08L1). (Most soil scientists would say 20-30 [2-3% organic carbon] is abnormally high for tropical soils that tend to average about 10 grams of organic carbon/ kg. of soil rarely more than 15 [1.5%].) Terra preta soils are often carbon-enriched down to as deep as 100-200 cm. below the ground surface. It is hard to understand why ancient Amazonians would endure all the work (with their stone tools) of creating terra preta much deeper than the depth of the root zone of their crops (about 25 cm.) unless they were growing fruit trees. (By about 4000 years ago, the indians of the lower Amazon were growing at least 138 varieties of crops. Between 50 and 80% of these varieties were trees (05M1). Ancient Amazonians planted these trees, often in the form of orchards. In today's world the ancient remnants of these orchards are called "fallows" (05M1).) Normal low-fertility tropical soils and soils globally have average organic carbon-enriched depths ("topsoil" depths) of about 25 cm. (Sub-soils worldwide have very low organic carbon contents.) When modern-day man creates terra preta over large areas, depths are unlikely to exceed 25 cm. So the conservative assumption is made here that modern terra preta will have a depth of 25 cm.

The total amount of organic carbon stored per unit area of terra preta cropland is therefore about 15 times that in normal, low-fertility tropical soils (08L1) although this sounds like it may be an upper limit as suggested by the words "up to" above. However other sources give factors of 20 (07F3) and 25 (07P1). An average of these three sources gives a factor of 20. Thus, were one to convert all tropical soils to terra preta, the amount of carbon that could be drawn from the atmosphere (as CO2 via photosynthesis) and provided with permanent storage ("sequestered") in the global tropical soil sink would be 504 x 20 or about 10,000 Gt. C. It is far more realistic to assume that conversion of tropical soils to terra preta soil is justified only in croplands, i.e. in only about 14.7% of the world's tropical soils. In that case, the size of the carbon sink created by converting all tropical croplands to terra preta would be about 1470 Gt. C.

The first step in the process of converting tropical cropland soils would probably involve creating "biochar" by burning wood chips in an oxygen-poor environment (pyrolysis) to burn off about half of its carbon. The overwhelming use of wood in tropical countries is for fuel for cooking and heating, because people with a median income of $2/ person/ day cannot afford fossil fuels. Tropical farmers (about 50-75% of tropical economies) interested in converting their cropland soils to terra preta would probably choose to pyrolyze their wood to gain 50% of the heat value from the wood and then bury the rest to create terra preta. This would make the overall process far more energy-efficient than separating cooking/ heating wood from terra preta wood. It would also release far less CO2 into the atmosphere.

The second step of the conversion process would probably involve the collection of all the organic matter the farmers could lay their hands upon. The large variety of types of organic matter that ancient Amazonians used in their terra preta suggests that these people were well aware of the importance of organic matter in their terra preta. Their use of a wide variety of types of organic matter probably reflected the need for a soil environment conducive to obtaining the soil microorganisms that increase soil fertilities the most and/or the fastest. This organic matter, when buried in a soil environment containing "biochar", is the source of the organic matter needed to raise the organic matter content (and hence fertility) of the soil. ("biochar" stabilizes this organic matter against mineralization and leaching.) If one compares the amount of photosynthesis going on in tropical woodlands with that going on elsewhere in the tropical environment, it becomes clear that available non-woody organic matter is probably, at best, 10% of all tropical organic matter. A little math shows that utilizing all possible non-woody tropical organic matter would raise soil fertilities only very slowly. For this reason, some woody matter (e.g. tree foliage, twigs, and roots) would probably have to supplement the non-woody organic matter supply allocated to burial in the soil in order to adequately compensate tropical farmers for their efforts.

Farmers would be expected to use two classes of organic matter. The first would be forms of organic matter that get naturally incorporated into the soil: crop residues, tree roots from woodlands that previously occupied the cropland site, and soil surface litter. The second class (the hard part) would be organic matter that would have to be collected first: human excrements, livestock manure, food wastes, dead animals, dead branches + tree foliage + forest ground cover obtained from nearby woodland, etc. To this class would have to be added bits of wood that had not been pyrolyzed in order to wind up with an adequate supply of organic matter. In order to minimize labor and maximize the rate at which "biochar" stabilizes organic matter against mineralization, "biochar" and organic matter would need to be mixed together and then buried together in the soil. This burial would be the third and final step in the conversion of tropical cropland soils to terra preta. The first burial would have only 3-10 years to stabilize organic matter against mineralization. This might not be enough time so perhaps fertility improvements might require a second or third annual burial of "biochar" and organic matter to begin achieving significant fertility improvements. Effects on global warming come from both burial of "biochar" and stabilization of organic matter. So these effects would probably occur somewhat sooner.

In order to halt the increase in atmospheric greenhouse gasses during the 21th century, the terra preta's carbon sink would have to draw (via photosynthesis) greenhouse gasses out of the atmosphere as fast at the current rate of growth of these gasses (3.8 Gt. C/ year (00P1) (08U1)). This rate is expected to roughly double by the end of the 21st century (02M2), suggesting that the terra preta soil sink for carbon would have to be capable of sequestering about 524 Gt. C out to the year 2100 (311 out to 2050). To reduce the global mean surface temperature of the earth sufficiently to stop melting of the Greenland ice cap and the shrinkage of the world's glaciers, the terra preta sink would have to sequester an added 100 Gt. C as described earlier. So the total size of the terra preta carbon sink would have to be at least 624 Gt. C by the year 2100 and 411 Gt. C/ year by 2050 (assuming we want to stop the melting of the Greenland ice cap and halt glacier shrinkage by 2050). The terra preta sink-size for tropical croplands estimated above is 1470 Gt. C.

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~ [5B] ~ Is it reasonably possible for biochar and organic matter to be added to tropical soils at a rate sufficient to exceed the rate of growth of atmospheric carbon?
First, let's make sure we understand the basic concept behind using terra preta to halt and reverse global warming as described in Section [2] above titled "Some Essential Soil Chemistry Basics." In ordinary tropical (or temperate) soils, the introduction of organic matter into the soils via crop residues, tree roots, soil surface litter and other forms of organic matter that get naturally incorporated into the soil, plus organic matter such as human excrements, livestock manure, food wastes, dead animals, tree foliage, and various other carbon-containing (organic) wastes that humans could deliberately bury in the soil (all products of photosynthesis) normally results (over the following roughly 3-10 years) in "mineralization" ("decomposition") of this organic matter. As a result, the carbon in this soil organic matter escapes into the atmosphere as CO2 - right back where it came from initially - before photosynthesis created the organic matter. The net result on global warming is zero or nearly so.

On the other hand, in terra preta, the naturally (or deliberately) added organic matter is stabilized by attaching chemically to the surfaces of "biochar" that humans added to the soil in the initial creation of terra preta soils. As a result, the half-live of the added soil carbon becomes thousands of years rather than 3-10 years typical of non-stabilized organic matter. The net result is that photosynthesis removes the photosynthesized carbon essentially permanently from the atmosphere, thereby slowing, or reversing, global warming. During the following year, more organic matter must be naturally or deliberately added to the terra preta soil if one wants to continue slowing, or reversing, global warming. One must also add more "biochar" unless one buried more biochar in prior years that is needed by the added organic matter. The act of adding "biochar" also permanently removes atmospheric CO2 from the atmosphere as a result of prior photosynthesized CO2 when the "biochar" was created. This is because the half-life of wood as "biochar" in soils is on the order of 5000 years or more, as compared to a half-life of ordinary wood in soils of roughly 3-10 years.

From the above it should be clear that there is a limit to how fast terra preta can remove carbon from the atmosphere. This limit is roughly equal to the amount of organic matter (plus "biochar") that farmers add to their terra preta soils each year (unless excessive amounts of organic matter and "biochar" were added in prior years. This limit, in turn, is imposed by the amount of photosynthesized organic matter that is accessible to terra preta farmers. If the world's terra preta cannot remove carbon faster than the usual (before terra preta) rate of increase of atmospheric carbon (3.8 Gt. C/ year), the only result would be a slowing of the rate of global warming. If the world's terra preta can remove carbon from the atmosphere faster than the usual (before terra preta) rate of increase of atmospheric carbon (3.8 Gt. C/ year), then global cooling would replace global warming.

The global rate of photosynthesis over land is about 62 Gt. C/ year (02M2) (15 from ground vegetation + 22 from non-woody parts of trees + 25 from woody parts of trees). Photosynthesis in the world's oceans (60-80 Gt. C/ year) is not included in the over-land rate (02M2). The rate of photosynthesis occurring in the world's tropical forests is 26 Gt. C/ year. This is composed of 19.7 Gt. C/ year for the 17.0 million km2 of tropical forest plus 6.3 Gt. C/ year for the 7.5 million km2 of tropical seasonal forest. (See Ref. (07S2) Ch. 3 Sect. [C]. The data there are normalized to give the same global rate of photosynthesis as that given in Ref. (02M2) noted above.) The photosynthesis that occurs in tree roots and tree foliage is not realistically accessible to shifting cultivators or anyone else for the purpose of creating the "biochar" needed to create terra preta. Tree roots and tree foliage are accessible to the creation of more soil organic matter that could be stabilized against mineralization and serve the same purpose as "biochar" in reducing global warming and also in enhancing soil fertility.

The data available on biomass partitioning for trees (See Ref. (07S1) Ch.2, Section [B].) suggests that about 78% of tree biomass (and hence photosynthesis) is not located in the roots or foliage. In addition, understory accounts for less than 2% of the biomass in a tropical forest, but some of this could be used for increasing soil organic matter. Perhaps an additional amount equivalent to 10% of tropical forest photosynthesis could be stabilized against mineralization in terra preta soils and serve the dual purpose of enhancing soil fertility and reducing the net rate of greenhouse gas emissions. Therefore about 88% of the photosynthesis in the world's tropical forests is accessible for reducing the net rate of greenhouse gas emissions into the atmosphere. This amount (88% of 26 Gt. C/ year) is 23 Gt. C/ year. This amount, if captured in terra preta, is larger than the amount (3.8 Gt. C/ year) needed to halt global warming now, and larger that the amount (7.6 Gt. C) needed to halt global warming in the year 2100. If one also wants to cool the global mean surface temperature to prevent ice-cap melting and receding of glaciers by 2050 a sequestering rate of 6.2 Gt. C/ year would be required. This is still within the abilities of a terra preta sink. It is also quite clear than in today's tropical forests, very little is not accessible to man (07S1).

Forest biomass without biomass removals increases at the rate of 1-3%/ year. For tropical forests, a biomass growth rate of about 2%/ year is probably typical. If one extracts biomass faster than this, the forest inventory is reduced over time and this decreases the rate of photosynthesis over time and so is counter-productive. If man extracts 2% of tropical forest biomass and converts it to "biochar" or to organic materials that are stabilized against mineralization or leaching in terra preta, one is essentially extracting the above-mentioned 23 Gt. C of photosynthesis.

One must also take into account the fact that, in the pyrolysis process used to create "biochar", about 50% of the carbon is burned off, and this returns back to the atmosphere as CO2. This could significantly reduce the above-mentioned 23 Gt. C. This does not necessarily need to be. If the heat generated in the pyrolysis process replaces the heat generated for some purpose by the combustion of fossil fuels or by the combustion of tropical wood harvests for heating and cooking, there would be no net reduction in the above-mentioned 23 Gt. C. This is easily accomplished at shown in the paragraphs above. The current rate of increase in atmospheric carbon mentioned earlier is 3.8 Gt. C/ year. So terra preta is readily capable of both halting and reversing global warming. This is basically a consequence of the fact that "biochar" buried in soil has a half-life of about 5000 years or more. Organic matter stabilized against mineralization by buried "biochar" apparently has a similar half-life given the organic matter content of 7000-year-old terra preta. This should be compared to the half-life of ordinary (non-pyrolyzed) wood chips and organic matter in soil of 3-10 years.

Others have calculated that a strategy combining "biochar" production (a key ingredient of terra preta) with bio-fuel production could ultimately offset 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 atmospheric greenhouse gas would stop increasing. If so, the only greenhouse gas that terra preta would need to remove would be the current carbon excess inventory of roughly 100 Gt. This process should not be counted upon, however, because the more likely process for producing "biochar" would be carried out by "slash-and-char" farmers who had converted from "slash-and-burn" (shifting cultivation) agriculture.

Sequestering large 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 "biochar" 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 405 "dead zones" in the world's oceans (08B2). 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 human health considerations. Reducing chemical fertilizer consumption would make the world's food supply less dependent on energy (fossil fuel) 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.

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~ [6] ~ Slash-and-Burn vs. Slash-and-Char ~
In a terra preta-free environment (essentially the current situation), much (half?) of tropical agriculture is known as "slash-and-burn" or "shifting cultivation." Estimates done earlier in this document find the area of shifting cultivation agriculture only a little less than that of normal tropical agriculture. Shifting cultivators clear small patches (a few ha.) of tropical forest and then burn the fallen trees to produce various gasses, mainly CO2, a greenhouse gas, and ash which is mainly minerals that enrich 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. The number of "slash-and-burn" farm families in the modern-day tropical world is in the hundreds of millions -more that what the world's tropical forests can support. (For details on the effects of "slash-and-burn" agriculture on tropical forests, see Ref. (07S1)) As a result of this over-population, today's "slash-and-burn" farmers must return to the same plots of land 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 "slash-and-char" process produces "biochar" 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 "biochar." 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 "biochar," a key part of any process for creating terra preta that soil scientists ought to be able to come up with. Also this process produces "biochar" 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.

Currently "slash-and-burn" farmers would reject the idea of replacing the usual ash by "biochar" because ash provides soil nutrients and "biochar" 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 "biochar" so created to create terra preta on the "slash-and-char" farmer's plot like the Amazonians probably did in past millennia? The result would be significantly 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. Less tropical forest would be consumed because new plots of forest would not have to be cut and burned every three years. The farmers' families would be better fed than 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 hundreds of millions of rural people 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. "Slash-and-burn" farmers are among the world's poorest people, and the world's poorest regions are the regions that continue to have the highest total fertility rates (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 ancient Amazonians somehow managed to learn with stone tools and without any written language to transmit acquired knowledge from generation to generation. Actually there is even more at stake than these paragraphs suggest. Section [8] below goes into other 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 convert low-fertility tropical cropland soils into terra preta. 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 forests. These people would have both the ability and the resources to create "biochar." They would also have a significant incentive to learn the new technology in the form of significantly increased soil fertilities and reductions in the amount of agricultural labor requires as a result of the ability to stay on one plot of cropland longer, if not indefinitely. The "biochar" apparently stabilizes ("sequesters") this organic matter for thousands of years on the extremely large internal areas of mineral surfaces that "biochar" possesses. That organic matter would otherwise be almost entirely "mineralized" on a time frame of 3-10 years 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, converting these farmers to "slash-and-char" farmers. 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 nations. This is particularly so because 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 scale could pose serious risks to this vision of Brazil's future however. But given the increased incentive to clamp down on illegal logging (the increased wealth generated by terra preta), Brazil and other tropical nations would probably find ways of reducing, or eliminating, illegal logging. Developed nations and China would also have a strong incentive to block the importation of illegally harvested tropical timber because that would reduce the risks to the terra preta solution to global warming.

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~ [7] ~ The Effects of "Slash-and-Char" on Tropical Forests ~
Admittedly the effects of replacing "slash-and-burn" agriculture by "slash-and-char" terra preta-based agriculture on tropical forests are not clearly established. This is because the recipe for large-scale creation of terra preta is not yet known. More specifically, we do not know how much "biochar" a given area of terra preta will require. However the possibilities look intriguing. For example, assume that a "slash-and-char" farmer can produce enough "biochar" from an acre of tropical forest to satisfy the needs of an acre of terra preta cropland. In that case, the farmer is set for life. Instead of burning additional patches of tropical forest every three years or so for the rest of his/her life, he/she burns only one patch or at least fewer patches. In that case, significant reductions in tropical forest burning could result. The carrying capacity of tropical forests under "slash-and-burn" agriculture is widely known to currently be about 10 people per square kilometer (84G1). The current population significantly exceeds this limit, resulting in shorter fallow periods, even less productivity and even more hunger. Terra Preta agriculture would significantly increase the carrying capacity of tropical forests. Recall that widespread use of terra preta in Amazonia is reputed to have spawned a great civilization in past millennia (05M1) - something that "slash-and-burn" agriculture could not 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 in their 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 more than in the EU on a pounds-of-fertilizer-per-hour-of-labor basis. Africa's soils are being mined of their nutrients. 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 "biochar" (wood 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 "biochar" 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 decrease as a result of "slash-and-char" farmers not having to abandon infertile croplands as frequently, if at all. Appendix I provides 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 21st 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 Abnormally Low Global Mean Surface Temperatures ~

The terra preta strategy for dealing with global warming offers major benefits relative to other strategies. Among them are simplicity, low cost, political viability, and the ability to reduce the concentration of atmospheric greenhouse gasses (via photosynthesis). However these advantages come with a potential for producing excessively low global mean surface temperatures. The risk comes, in large part, from probable conflicts between farmers interested in increasing soil fertilities and others who are primarily concerned about maintaining a satisfactory global mean surface temperature. That potential could be increased by:

Being able to double or triple the fertility of one's croplands could precipitate an enthusiastic response to terra preta technology - perhaps too enthusiastic. Terra preta could eat away at the atmospheric greenhouse gasses to the point of making the global mean surface temperature significantly cooler than croplands in temperate climates need, among other things. Alternatively, the issue of declining marginal productivities of terra preta soil-building efforts could cause tropical farmers to see no economic need to convert their soils to terra preta to the degree required to sequester the amount of carbon required to fully address the global warming issue. The increased tropical food supplies could decrease food prices (given the typically high degrees of inelasticity in demands for food) sufficiently to degrade the economics of conversions to terra preta. This too could create problems for those concerned about global warming. These problems might be dealt with to some degree by carefully designed subsidies.

Clearly there are too many unknowns at this point to produce reliable estimates of the risks of excessively low global mean surface temperatures, although there are obviously risky scenarios that should be kept in mind. Once terra preta science and technology become better understood, the degree of speculation on this risk would probably be reduced to acceptable levels.

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~ [10] ~ Kyoto Views toward the Terra Preta Strategy
The Kyoto protocol on solving the global warming problem does 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 probably because they see such stored organic carbon compounds as mainly temporary, with virtually all of it being "mineralized" back into CO2 or CH4 and then released back into the atmosphere within a decade or so. This is true for essentially all the world's soils. What the Kyoto protocol is in denial of is the fact that terra preta, in tropical soil environments will be 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. Then terra preta will provide a sink for the organic carbon that photosynthesis draws from the atmosphere's supply of CO2 - a sink larger than that needed to eliminate global warming (See above). The Kyoto protocol is correct in the sense that modern day soil scientists are still working on replicating the ability of the ancient Amazonians to create terra preta on a large scale. Once such a process has been developed, the position of future protocols is almost certain to change. Consider:

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~ [11] ~ Terra Preta's Competitors: A Comparison of Alternatives ~
The terra preta strategy is outside the main stream of thinking about how best to deal with global warming. Also, even though the basic chemistry of the process that produces sequestering in terra preta is well established, a detailed description of what the terra preta strategy would entail is still lacking. However, in the final analysis, the choice of a combination of strategies for dealing with global warming ought to be based on a comparison of all the options, not on some sort of absolute judgment. This comparison of options is done below. Omitted from the list of considered options is the zero option - subjecting mankind to the "big-ticket costs" of global warming.

Sparing mankind from the "big-ticket" costs of global warming described below requires:

[1] ~ Reducing the net annual loading of atmospheric carbon from 4 Gt. to 0 Gt. and

[2] ~ Removing an additional roughly 100 Gt. C within a matter of a few decades to reduce the global mean surface temperature to the point where the Greenland ice cap stops its net melting, and the world's glaciers stop receding.

Recall that the melting of Greenland's ice-cap risks flooding vast areas of coastal plains under about 25 meters of water, while disappearance of the world's 10,000 or so glaciers risks the continuity of water flow to half the world's population, half the world's irrigated area, and therefore 30% of the value of the world's food supply. A prime example of a "big-ticket cost" is Bangladesh that is nearly all on a coastal flood plain. Sea-level increases are already causing the cropland soils, trees, water tables and other essentials for life in Bangladesh to suffer heavy damage from salt-water intrusions. Clearly, global warming, unless reversed, will cause Bangladesh to cease to exist, and its 150 million people will have no place to go. India is already building fences along its boundary in preparation. Bangladesh's other neighbor, Burma, could not even begin to accommodate such seas of humanity (08H1). Sparing mankind from these "big-ticket costs" of global warming requires removal of roughly 100 Gt. of carbon from the atmosphere well before Greenland's ice cap and the bulk of the world's glaciers are gone, i.e. within roughly 50 years, i.e. at a rate in excess of roughly 2 Gt. C/ year. This comes from the calculation that the melting of Greenland's ice cover is estimated to produce a 25-meter increase in sea levels by the year 2100 (08H1).

Accomplishing Objectives [1] and [2] purely via reducing fossil fuels combustion would require reducing that combustion rate by over 100% (5.4 to minus 0.6 Gt. C/ year) via some combination of:
[1a] ~ Reducing the need for fossil fuels combustion by increasing nuclear power generation
[1b] ~ Reducing the need for fossil fuels combustion by increasing solar- and wind-power generation
[1c] ~ Reducing the need for fossil fuels combustion using energy conservation.
That virtually impossible burden on these three options could be lessened via some combination of the following options for additional sequestering of greenhouse gasses into various sinks:
[2a] ~ Sinks composed of increased inventories of forest biomass,
[2b] ~ Sinks composed of pressurized containers of liquid CO2, and
[2c] ~ The terra preta sink described above.

It is important to note, however, that the earth has already reached a global mean surface temperature sufficient to produce a net annual melting of the Greenland ice cap, and also sufficient to eliminate the world's 10,000 or so glaciers. As a result, it is now physically impossible to avoid the "big-ticket" costs of global warming by merely decreasing the rate of consumption of fossil fuels, e.g. via various "cap-and-trade" schemes, or via various conservation measures or via the nuclear power option or via pressurized containers of liquid CO2 option. These are laudable in their own right, but all they can accomplish is a slight postponement of the "big-ticket" costs of global warming. Thus Options [1a], [1b], [1c], and [2b] are not worth considering further, although they are evaluated below to point out other problems associated with these options for use by people who cannot let go of these options.

The forest biomass sink: Keeping mankind safe from the "big-ticket" costs of global warming out to the year 2100 requires halting the increase in atmospheric greenhouse gasses during the 21th century. This means that a soil-carbon sink would have to draw (via photosynthesis) greenhouse gasses out of the atmosphere as fast at the current rate of growth of these gasses (3.8 Gt. C/ year (00P1) (08U1)). This rate is expected to roughly double by the end of the 21st century (02M2), suggesting that the soil-carbon sink would have to be capable of sequestering about 524 Gt. C out to the year 2100 (311 out to 2050). To reduce the global mean surface temperature of the earth sufficiently to stop melting of the Greenland ice cap and the shrinkage of the world's glaciers, the soil-carbon sink would have to sequester roughly an additional 100 Gt. C. So the total size of a soil-carbon sink would have to be at least 624 Gt. C by the year 2100 and 411 Gt. C/ year by 2050 (assuming we want to stop the melting of the Greenland ice cap and halt glacier shrinkage by 2050). The terra preta (soil) carbon sink-size for tropical croplands has been shown to be about 1470 Gt. C -easily sufficient for the required task. Now let's examine how big a forest area dedicated exclusively to carbon sequestering would need to be to accomplish the task of halting and reversing global warming.

Creating a forest biomass sink entails creating a new area of forest and keeping it undisturbed indefinitely. (Net biomass growth eventually stops after roughly 150 years for temperate forests and roughly 100 years for tropical forests.) That forest would have to be protected indefinitely from conversion to other land uses, logging, pests and fires. All four of these tasks are becoming increasingly difficult in today's environment of increasing population pressures on the land, increasing demands for wood fiber, increasing numbers of forest pests and increasingly rapid movement of forest pests worldwide due to globalization, and increasing aridity and temperatures due to global warming. Little wonder then that the world's forests are undergoing deforestation (07S1) and serve as a source of 1.1 Gt. C/ year (05F1), not as a sink. A large fraction of the deforestation in developing nations is (1) done illegally, and (2) not recorded in global timber harvesting statistics and (3) difficult 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 best place for creating a forest for the sole purpose of sequestering carbon is in tropical lands. The world's 24.5 million km2 of tropical forest would contain a plant-carbon mass of 461 Gt. in its natural condition (75W1) (Also see Part [A5] of Chapter 3 of Ref. (07S1)). It would be hard to imagine allocating a land area more that roughly 10% of the world's exists area of tropical forest to the sole purpose of sequestering carbon. There are too many competing needs for the land. In that case, a sink would be created with a sequestering capacity of about 46 Gt. C. This capacity would be reached after tree biomass growth stops, i.e. after roughly 100 years. Assuming a linear biomass growth rate over the first 100 years would produce a sink in the year 2100 of 41 Gt. C (19 Gt. C in the year 2050). This carbon sink would be subject to the four significant risks alluded to above.

Also keep in mind the high costs involved in the initial creation such a vast forest, and then of perpetually managing this sink that would cover 2.45 million km2 (about one million square miles). Imagine the cost of guarding every square mile perpetually against conversion to other land uses, illegal logging, fires and invasive species. It is far from clear that future international meetings on global warming would be willing or able to come up with this kind of money indefinitely. This should be seen as the fifth major risk threatening the viability of the forest-based carbon sink option. It thus becomes fairly clear that the costs and the four other major risks associated with the forest biomass option, even for an area that is much too small to halt and reverse global warming, makes further consideration of this option not worthy of the effort involved. This leads to the conclusion that the only viable option for halting and reversing global warming and sparing mankind from the "big ticket" costs of global warming is the terra preta option.

Pressurized containers of CO2: Another possible sink for reducing the rate of greenhouse gas introduction into the atmosphere involves pressurizing the greenhouse gases that come from large fossil fuels combustion systems (e.g. power plants) to liquefy these gasses. These ever-increasing amounts of pressurized liquids would have to be stored in some sort of (underground?) vault indefinitely. The complexity and perpetual cost of such collection/ pressurization/ storage systems capable of sequestering significantly more than 1 Gt. C/ year (3.66 billion tonnes of CO2/ year) defy comprehension. That sequestering rate implies a sequestering of 50 Gt. out to 2050 and 90 Gt. out to the year 2100. These figures neglect the energy costs involved in container construction, pressurization, and storage. It is not clear that future international meetings on global warming would be willing or able to provide the huge amounts of money needed to sequester one billion tonnes of liquefied greenhouse gasses every year for even a century. This creates a huge additional risk to this option. Power sector emissions make up 25% of the global total of carbon emissions (40% of the total in the U.S.) (07C1). So sequestering CO2 emissions in pressurized containers would be virtually impossible to achieve beyond a little over 1 Gt. C/ year even if every industrialized nation on earth were to sequester 100% of their power plant emissions in pressurized containers. As noted above, this option does not allow for extraction greenhouse gasses from the atmosphere, and thus is unable, even theoretically, to halt and reverse global warming and spar mankind from the "big ticket" costs of global warming. Also note that, at the scale examined above (probably the maximum possible scale that could rationally be considered), this option is insufficient to the task of successfully dealing with global warming.

The nuclear power alternative to fossil fuels combustion: Another strategy for reducing the rate of greenhouse gas introduction into the atmosphere involves large-scale conversions from fossil-fuel-powered power plants 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. A 2005 report by the Asia Pacific Foundation of Canada predicted a 45,000-tonne shortage of uranium in the next decade, largely because of growing Chinese demand. (China intends to build 40 new nuclear power stations by 2020.) Prices for uranium almost tripled between March 2003 and May 2005. Uranium mining production peaked in 2001. Also, the creation of nuclear fuels from natural uranium and the reprocessing and sequestering of spent nuclear fuels require huge amounts of energy. Nuclear power tends to be heavily subsidized by governments, and even then, Lovins et al argue that the cost to the consumer is significantly above that of power from fossil fuels plants.

Clearly, the constraints on uranium fuel supplies, the subsidies, and the higher cost of nuclear power will prevent the large-scale replacement of fossil fuels in most of the developing world and much of the developed world. But one cannot deny the possibility of nuclear power replacing perhaps an additional 10% of the world's current fossil fuels consumption. This would imply a reduction of the contribution of fossil fuels to greenhouse gas emissions of 0.54 Gt. C/ year. This suggests the elimination of 23 Gt. C by 2050 and 50 Gt. C by the year 2100. The risks posed by fuel supply constraint would increase with each passing decade. The potential for expanding the use of "breeder" reactors that create more fuel than they consume (still in the development stage) has apparently not yet been seriously considered. However, increasing uranium prices and fossil fuels prices over the next century could change that. As noted above, this option does not allow for extraction greenhouse gasses from the atmosphere, and thus is unable, even theoretically, to halt and reverse global warming and spar mankind from the "big ticket" costs of global warming. Also note that, at the scale examined above (probably the maximum possible scale that could rationally be considered), this option is insufficient to the task of successfully dealing with global warming.

The solar- and wind-power alternatives to fossil fuels combustion: The situation for solar- and wind power generators is quite different from that of nuclear power. There are no fuel supply risks. Also, as reserves of oil and coal diminish, prices would be expected to rise, making it increasingly easy, over time, for solar- and wind power to be financially viable in an ever-increasing number of environments. The outputs of the world's solar- and wind power generators are still a small fraction of the world's consumption of nuclear power and an even smaller fraction of fossil-fuels-generated power. However these renewable energy sources are expanding rapidly, and in some regions of the developed world they are, or could be, profitable without subsidies. However at today's fossil fuels prices it is far from clear that these power sources will replace any substantial portion of fossil-fuel-generated power in the developed world. A large fraction of today's developing world finds even fossil fuels to be beyond their means. Over time however, the outlook for solar- and wind power looks increasingly promising. A rough estimate would suggest that these options are likely to replace about a quarter of the estimated 100% growth of fossil fuels combustion between now and the year 2100. This would suggest an equivalent sink-size in the year 2100 of 32 Gt. C (13 Gt. C in 2050). As noted above, this option does not allow for extraction greenhouse gasses from the atmosphere, and thus is unable, even theoretically, to halt and reverse global warming and spar mankind from the "big ticket" costs of global warming. Also note that, at the scale examined above (probably the maximum possible scale that could rationally be considered), this option is insufficient to the task of successfully dealing with global warming.

The energy conservation alternative to fossil fuels combustion: Some nations, particularly those with high rates of fossil fuel consumption, could easily cut back on their fossil fuels consumption by 50% or more. Other nations, particularly poor nations with low rates of fossil fuels consumption, make frugal use of fossil fuels. This extreme disparity appears to be the reason why some observers in the Poznan meeting worried that too many differences remain to negotiate a broad international treaty on global warming. The Poznan talks ended with deep divisions between rich and poor nations. The failure of the 13 years of international meetings on global warming to accomplish much of anything is probably the result, primarily, of those deep divisions. Meanwhile the Greenland ice cap keeps melting away and the world's glaciers keep shrinking. It seems quite clear that continuing to allow this gridlock to persist any longer would be a serious mistake. It would be far safer to seek other solutions to global warming and let the inevitable escalation of fossil fuels prices determine energy conservation patterns. A rough estimate would suggest that energy conservation is likely to replace about a quarter of the estimated 100% growth of fossil fuels combustion between now and the year 2100. This would suggest an equivalent sink-size of 32 Gt. C. in the year 2100 and 19 Gt. C. in 2050. As noted above, this option does not allow for extraction greenhouse gasses from the atmosphere, and thus is unable, even theoretically, to halt and reverse global warming and spar mankind from the "big ticket" costs of global warming. Also note that, at the scale examined above (probably the maximum possible scale that could rationally be considered), this option is insufficient to the task of successfully dealing with global warming.

As of 2004, the crude oil outputs of 25 nations (including all of the Middle East and North America) have peaked, and are now in a state of decline. Most have been in a state of decline for several decades. The crude oil outputs of the remaining nine oil-producing nations continue to increase, but four of these nations have very small outputs, and a fifth nation (China) is in no mood to export oil. Coal gasification and liquefication are complex and expensive processes requiring high prices for outputs (91S1). Also these processes are highly dependent on the chemical and physical characteristics of the coal being inputted. High-oil-consumption nations are going to be hit hard economically, and are going to be compelled to finally get serious about energy conservation. This mechanism of determining how energy-conservation burdens are to be shared seems superior to accomplishing the task by international committee. Fossil-fuel combustion and rate of greenhouse gas emission are expected to roughly double by the year 2100. In the environment just described, this estimate would appear to involve a large measure of wishful thinking, but no one apparently knows how to make a better estimate.

Summary: Employing all of the above options (and neglecting the terra preta option) and expressing the results using the common denominator of sink-capacity gives an effective additional carbon sink capacity of roughly 245 Gt. C in the year 2100 and 130 Gt. C in 2050. Recall that the additional sink capacity required to spare mankind from the "big-ticket" costs of global warming is roughly 624 Gt. C in the year 2100 and 411 Gt. C in 2050. So full utilization of all the above options would provide an additional carbon sink with a capacity of 39% of the required size in the year 2100 and 32% in 2050. Even worse, the extremely high costs, every year, for the pressurized, liquefied CO2 sink and the extremely high costs and other serious risks for the forest biomass sink make it extremely doubtful that these two sinks could ever be politically or economically viable in future international meetings on global warming. Eliminating these two sinks would reduce the total additional sink size in 2100 to 114 Gt. C (18% of the needed 624 Gt. C) and to 61 Gt. C in 2050 (15% of the needed 411 Gt. C in 2050). Now recall that the terra preta option, applied to all tropical croplands, would provide another sink of roughly 1470 Gt. C. This would be sufficient to make up the 379 or 281 Gt. C shortfall, and sufficient to even neglect all the other options entirely. Also, the terra preta sink size would materialize fairly early, well before the year 2100. This would give much added insurance against mankind having to endure any, or most, of the "big-ticket" costs of global warming as defined earlier in this document.

The risks inherent in the terra preta option appear to be far less than those of the other options, primarily because the economic costs of this option are so low and the side effects are so appealing. The terra preta option achieves its extremely low cost by using its main side-effect (doubling or tripling the fertility of tropical cropland soils) to compensate tropical farmers for converting their cropland soils to terra preta. The analysis of options given above makes it clear that any set of options that exclude the terra preta option is incapable of addressing the "big-ticket" costs of global warming, and by a large margin. Thus it is hard to avoid the conclusion that including the terra preta option is the only way of avoiding the "big-ticket" costs of global warming.

Terra Preta Politics: When President Obama proposes his plan for dealing with global warming, his critics are certain to point out the miniscule amount of slowing of the rate of increase in the earth's global mean surface temperature that Obama's plan promises. They are also sure to point out the lack of comparable commitments from almost every other nation. They are also certain to point out the massive cost of achieving so little. President Obama will be forced to spend down a lot of political capital - capital that he badly needs for the many other commitments that he has made. The risk of being unable to get President Obama's global warming plan through Congress is high. It is time to review our strategies and options. These political capital costs and legislative risks are easily avoided by adopting an effective, low-cost option for halting and reversing global warming.

The times are now ripe for an enthusiastic welcome for terra preta technology. We have all those nations getting increasingly and extremely pessimistic about ever addressing global warming to the degree required to address the "big-ticket" costs of global warming. We have all those industries worried about how much "carbon credits" are likely to cost them. We have all those environmental organizations that, sooner or later, will do a little math and come to the realization that the strategies they are pushing have essentially zero probability of eliminating the "big-ticket" costs of global warming. We have a president with the right attitude toward global warming, and who is probably concerned about the high cost (in both money-terms and political capital terms) of addressing global warming by focusing on high-cost-high-risk strategies. All that is needed now is a national environmental organization that is willing to do some homework and thereby become bold enough to move the terra preta strategy into the arenas of public discourse.

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~ [12] ~ 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 and their predecessors have been on-going since around 1995 [COP-1 in Berlin]. Yet they show no signs of accomplishing anything beyond token gestures. The effects of such gestures 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 their commitment in mid-2008 (08B1). At this point there is almost unanimous pessimism about the possibilities for success at the international meeting in Copenhagen in late 2009. Also there is near total disagreement as to how the burdens of emissions reductions are to be shared among the world's 190 or so nations. The most serious bone of contention revolves around burden-sharing between the developed world and the developing world. There are far better ways of resolving that bone-of-contention outside the format of an international conference, as described above. The Kyoto Protocol expires in 2012.

The "big-ticket" costs of global warming suggest that few of the earth's inhabitants will escape the consequences of these costs. Glacier melting, which is happening worldwide, threatens the continuity of water flows to half the people on the planet, and hence the viability of about half of the world's irrigation systems. (The world has about 10,000 glaciers (02M1).) The world's irrigation systems provide 60% of the world's food supplies on a dollar-value basis, suggesting a threat to roughly 30% of the world's food supplies. Sea-level increases are already causing the cropland soils, trees, water tables and other essentials for life in Bangladesh to suffer heavy damage from salt-water intrusions. From this we can conclude that 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 (08H1).

Carrying out the terra preta option, based on the analysis above, involves the following:

The international meeting-based approach for addressing global warming must be seen for what it is - a waste of time. It is also counterproductive, and has delayed a focus on a strategy with a greater potential, but without the hang-ups that have caused the international meeting approach to grind to a virtual halt and squander over a decade - a decade that could otherwise have been spent reducing the global mean surface temperature.

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Appendix I ~ Illegal Logging in Developing Nations - Some insights:
The success of the terra preta strategy for reducing and reversing the rate of global warming is extremely dependent of an adequate supply of tropical forests. This supply is under significant danger, mainly from illegal logging as documented below.

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 three times more likely to be governed by a military leader, four 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.

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~ References ~
75W1
Robert H. Whitaker, Gene E. Likens, "The Biosphere and Man", in Primary Productivity of the Biosphere, Helmut Lieth and Robert H. Whitaker, editors, Springer-Verlag, Berlin (1975).
84G1 Nicholas Guppy, "Tropical Deforestation: A Global View", Foreign Affairs (Spring 1984) 62, pp. 928-965.
91S1 Bruce Sundquist, Informal conversations with US Bureau of Mines personnel and engineers involved in Westinghouse coal liquefication and gasification development efforts.
91W1 World Bank, World Development Report 1991: The Challenge of Development, Oxford University Press (1991).

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.

95S1 R. F. Sage, "Was low atmospheric CO2 during the Pleistocene a limiting factor for the origin of agriculture?" Global Change Biology 1 (1995) pp. 93-106.
96P1 E.A. Paul, F.E. Clark, Soil Microbiology and Biochemistry, Edition 2, Academic Press Inc. San Diego, CA (1996).
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.

00P1 E.A. Paul and J. Kimble, "Global Climate Change: Interactions with Soil Properties," http://www.usgcrp.gov/usgcrp/nacc/agriculture/paul.pdf (Excellent resource - apparently never published - year of upload to Internet uncertain, but after 1999.)
00U1 United Nations Development Programme et al, World Resources 2000-2001: People and Ecosystems: the Fraying Web of Life, World Resources Institute, Washington DC (2000).

01P1 Prentice I. C. et al. The Carbon Cycle and Atmospheric Carbon Dioxide. In: Houghton J.T. et al., editors. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge and New York: Cambridge University Press; 2001. p. 187, 204.
01P2 Prentice I. C. et al. The Carbon Cycle and Atmospheric Carbon Dioxide. In: Houghton J.T. et al., editors. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge and New York: Cambridge University Press; 2001. p. 187.

02F1 Friends of the Earth, "Why the Earth Summit Matters", Guardian UK (5/19/02)).
02M1 Gord Miller (Environmental Commissioner of Ontario), Letter to the speaker of the Legislative Assembly, Special Report to the Legislative Assembly of Ontario "Climate Change: Is the Science Sound?" (11/19/02) 66 pp. http://www.eco.on.ca/english/publicat/sp05.pdf
02M2 Michael B. McElroy, The Atmospheric Environment: Effects of Human Activity, Princeton University Press (2002).

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.
05M1 Charles C. Mann, 1491: New Revelations of the Americas before Columbus, Alfred A. Knopf, New York (2005) 465 pp. (Pages 306-311 discuss terra preta. Pages 300-305 introduce the issue.)

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," Phil. Transactions of the Royal Society B 362 (2006) pp.187-196.

07C1 Center for Global Development, "Climate Change Transparency," (11/14/07) http://www.cgdev.org/section/initiatives/_active/climatechange/combating (visited 2/3/09)
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.windstream.net/bsundquist1/df0.html
07S2 Bruce Sundquist Topsoil Loss and Degradation -Causes, Effects, and Implications: A Global Perspective, Edition 7 (July 2007) http://home.windstream.net/bsundquist1/se0.html
07S3 Bruce Sundquist Grazing Lands Degradation - A Global Perspective, Edition 6 (July 2007) http://home.windstream.net/bsundquist1/og0.html
07S4 Bruce Sundquist Irrigated Lands Degradation - A Global Perspective, Edition 5 (July 2007)) http://home.windstream.net/bsundquist1/ir0.html
07S5 Bruce Sundquist Fishery Degradation - A Global Perspective, Edition 8 (July 2007) http://home.windstream.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).
08B2 David Biello, "Oceanic Dead Zones Continue to Spread," Scientific American (8/15/08).
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.windstream.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.windstream.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.windstream.net/bsundquist1/ifp.html 
08U1 (Unknown) "Trends in Atmospheric Carbon Dioxide - Mauna Loa," Energy Systems Research Laboratory, Global Monitoring Division, http://www.esrl.noaa.gov/gmd/ccgg/trends/ visited 12/6/08.

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