18 Terra PretaThe Mysterious Soils of the Amazon Antoinette M. G. A. WinklerPrins1 CONTENTS 18.1 Introduction ..235 18.2 What Are Terra Preta Soils? 235 18.3 Terra Preta Formation .237 18.4 Where Are Terra Preta Soils Located? ..237 18.4.1 Are These Soils only in Amazonia? .238 18.5 Terra Preta Soils and Amazonian Prehistory .239 18.6 T erra Preta Soils and the Future of the Amazon (and Other Tropical Places) ..241 18.6.1 Biochar .242 18.7 Conclusions 243 Acknowledgments ..243 Futher Reading .244 18.1 INTRODUCTION The popular imagery of the Amazon typically conjures up one of two views: rampant environmental destruction on the one hand, and pristine, virgin nature with still-untouched tribes on the other. Neither is a correct representation of the region; the reality lies in between, but the persistence of these imageries hinders a more realistic approach to the region. Terra preta (TP) (black earth) soils, the topic of this chapter, challenge both images as they indicate much more human agency in the landscape in the past, a challenge to the persistent pristine myth image, and they represent a way in which soils of the region can be made more sustainable without external inputs, thereby challenging the idea that the only development in the Amazon is the destructive conversion of rainforest into industrial agriculture and predatory forestry. In this chapter, I define and describe TP soils and consider how their existence has contributed to past interpretations of the region, and how knowledge of their formation can contribute to a more sustainable use in the future. 18.2 WHAT ARE TERRA PRETA SOILS? Terra preta, Portuguese for black earth, are part of a continuum of soils often referred to as Amazonian Dark Earths, Archaeologic Dark Earths, or Anthropogenic Dark Earths (ADEs). True or proper TP soils are by definition black or a very dark brown, and are at one end of the continuum of ADEs, which extends to the much lighter-colored terra mulata (TM) (brown earth) soils. ADEs are anthrosols, soils that exist in the landscape as a consequence of human activity, either 235 through incidental activity such as the accumulation of human waste (anthropic soils), or as the result of deliberate action (anthropogenic soils), most likely associated with long-term sedentary farming, that is, farming that stays in one place, in contrast to shifting cultivation where people and their crops move periodically. The key differential is that TP soils contain ceramic fragments (potshards), whereas TM soils typically do not. Current thinking is that TP soils are the result of human inhabitation, that is, that they formed as composted material accumulated via incidental human activity (often in debris piles referred to as middens), while TM soils are the result of deliberate manipulation of the soil to improve its quality for agricultural purposes. The degree to which ADEs are anthropogenic or anthropic is debated at length, as this has ramifications for viewing the ways in which people managed their resources in the past, and how they may be able to do so again in the future. However, for the purposes of this chapter, the point is that TP soils are the result of human activity and they represent human agency on the Amazon landscape. The dark color of this continuum of soils is because they all contain high levels of stable soil organic matter (SOM), on average three times higher than the background or nonanthrosols of the Amazon basin. In addition to their relatively high levels of organic matter, ADEs are high in most other measures of soil fertility such as cation exchange capacity (CEC), phosphorus, nitrogen, calcium, magnesium, and especially carbon. Their pH is much more neutral than the surrounding mostly acidic soils, ranging from 5.2 to 6.4. These chemical attributes result in soils that contain and retain plant-available nutrients. High SOM also improves soil physical properties as the organic matter plays a role in changing the porosity of the background soil matrix, resulting in soils that are better able to retain moisture. This attribute may seem irrelevant for a tropical rainforest location, but the reality is that many areas of the Amazon basin, especially the central Brazilian Amazon, experience a strong dry season that impacts nonirrigated agricultural potential. Also, background nonanthrosols in the region are often either high in clay content resulting in periods of excessive moisture, or exhibit sand-sized aggregates that result in rapid flow-through and poor water retention. Both of these issues are muted by the high organic matter content of ADEs. What has been mysterious about these soils is their ability to persist in a landscape that common ecological knowledge would dictate they could not. In the generally high humidity and high rainfall environments such as found in the Amazon basin, most nutrients in the soil mineralize and are leached out of the system quickly, and because of this, the vegetation of the region typically absorbs nutrients quickly from the soil once these have been released in the soil through decomposition or other processes. Why then have ADEs, dated to have formed up to 2500 years ago, continue to exist? Soil chemists studying ADEs have concluded that the unique nature of the carbon in these soils is the key to the stability of the organic matter in ADEs and the key to the mystery of the persistence of ADEs in this landscape. The carbon found in ADEs is aromatic carbon (also known as black or pyrogenic carbon) that is likely a consequence of the incorporation of charcoal into the soil. This particular charcoal is the result not of natural forest fires (there is charcoal found in the Amazon that is the result of fires; these were less frequent in the past, but are now more frequent due to both natural and human-induced disturbance and climate change), but due to slow, cooler burns associated with the use of fire as a management tool in sedentary agriculture (more about this in Section 18.3 below). Soils with this type of carbon are able to retain, even attract nutrients, resulting in more plant-available phosphorus, calcium, and nitrogen, as the aromatic carbon acts as a carrying agent for nutrients. Aromatic carbon is also known to be highly resistant to degradation. This recalcitrant form of SOM is why ADEs persist in a high-leaching environment. One aspect of ADEs that remain poorly understood, quite mysterious actually, is the microbial complexes associated with them. What is known thus far is that TP soils exhibit greater microbial diversity than background soils, and much of these populations are predominantly fungal. These microbial populations perform an important function in the maintenance of the high fertility of ADEs over time, possibly even contributing to the generation of nonpyrogenic black carbon. They also assist in the improved soil moisture retention of ADEs. 18.3 TERRA PRETA FORMATION The appearance of ADEs in the landscape has generated a wide variety of ideas about their genesis. Although early theories (in the late 19th and early 20th centuries) pointed to likely anthropogenic origins, later theories were convinced of geologic (sediments or volcanic) or ecologic origins. These nonanthropogenic theories of ADE formation that dominated in the middle of the twentieth century reflect the era in which they circulated, an era in which the cultural potential of the Amazon was thought to be quite low and it was inconceivable to believe that human action was responsible for such a valuable resource. The full acceptance of their human origins did not come about until the last few decades, paralleling radically new findings in archaeology and anthropology regarding human activity and cultural achievement in the past (further discussed in Section 18.5 below). Questions about the differences and/or similarities between ADEs and Histosols (organic soils) persist, but ADEs, though they contain high levels of organic matter, are not Histosols. Histosols are typically located low in the landscape, in a position of accumulation of organic debris and moisture. There are plenty of Histosols in the floodplain areas of the Amazon, but most ADEs are not located in the floodplain and are typically well drained. Most importantly, once Histosols are drained and their organic content exposed to air, the organic matter quickly volatizes and the soil subsides. This is not the case with ADEs. What is clear today is that ADEs formed in situ and from the top, as their mineralogical composition is always the same as the surrounding soil. This helped dismiss the ideas that ADEs were the result of sedimentary processes. Evidence of midden formation around villages helps confirm in situ formation. In addition, scientists postulate that agricultural practices in the past included slash and char, a variant on the well-known slash-and-burn agriculture. Slash and char involves the use of a much cooler, slower burning that is actively managed, through long-term smoldering. Instead of letting biomass burn until ash as is typically done in present-day slash-and-burn agriculture, biomass is charred to the desired charcoal, containing the critical aromatic carbon, which is then used as a soil conditioner and incorporated into the soil over time. Evidence of slash and char comes from observing soil management practices today as practiced by people indigenous to the region. Research with smallholder agriculturalists that I have conducted with Brazilian colleagues has documented the formation of a soil conditioner called terra queimada (TQ) (burnt earth). This is created by first sweeping mostly organic refuse into piles where it is left to smolder for an extended period of time, and then the charred residue is applied to desired crops. This process has been observed throughout the basin by anthropologists and geographers. Long-term research with the Kayap Indians by Susanna Hecht has found a similar process, a practice called in-field burning, in which small, cool and slow burns are used to reduce weeds and other biomass within fields to produce char, which is then incorporated into the soil. Interestingly, todays refuse piles contain nonbiomass materials as well, especially plastic, aluminum, and batteries because in places where there is no regular refuse collection (much of the Amazon region), there is nowhere to go with this trash. Clearly, these materials change the chemistry of the char. Locals acknowledge that it may not be good to burn these materials but do not know what else to do with them. In cities, there are increasing efforts to collect trash, even in the informal settlements, so what is burned is more likely to be mostly debris from biomass, but in rural areas, the composition of the char likely contains remains of nonbiomass items. Much further research into the composition of present-day char is needed to fully understand the degree to which TQ may be an analog to what Amerindians were doing in the past. 18.4 WHERE ARE TERRA PRETA SOILS LOCATED? TP soils are patches within a landscape consisting mostly of highly weathered and acid tropical soils known as Latosols and Acrisols (or Oxisols and Ultisols in the USDAs Soil Taxonomy). Their individual extent is not large, most patches range in size from 2 to 350 hectares, with the majority being at the smaller end of that range. The Amazon Basin is of continental size, about the size of the lower 48 states of the U.S.A., and consists mostly of Brazilian territory, but also extends into neighboring Bolivia, Peru, Ecuador, Colombia, Venezuela, and the Guianas. It is estimated that ADEs cover approximately 3% of the basin, although observers of these soils note that it is likely that, once all ADEs are identified, their extent may be as high as 10% of the basin, which would be an area the size of France. Because of their generally small individual extent, ADEs rarely appear as individual classes of soil on soil maps of the region, but are inclusions in more spatially extensive soil classes. The full extent of TPs/ADEs is not known since the Amazon has not been subject to a full fieldbased systematic soil survey, so it is highly likely that there are many more patches of these soils. The best map we have to date is one that I created with a colleague and is available as an interactive Geographic Information System (GIS). More information about this GIS and associated database is available in the WinklerPrins and Aldrich 2010 publication. ADEs are mostly located on bluffs along the main-stem Amazon River (known as the Solimes River between the Brazil/Peru border and the city of Manaus) and its many tributaries. Their location there is likely for two reasons: (1) bluffs are easily accessible via what remains the main form of transportation in the Amazon, river transport, and therefore ADEs in those locations are best known to local Indian and Mestizo populations (who typically live on bluffs) and have been reported to scientists who have documented them in such a way that others know about these locations. (2) Amerindian populations before the arrival of Europeans were predominantly bluff dwellers. Bluffs are topographically advantageous in a flat landscape such as the Amazon, and bluff locations enabled access to resources from the rich riverine environment (e.g., water, fish, turtles, and naturally fertile floodplain soils) as well as those of the nonflooded uplands (e.g., fruit, meat from hunting, medicinals, and lumber). The geographer William Denevan has made a compelling case for the dominance of prehistoric bluff settlement in his 1996 paper given the complementary resources of the upland and floodplain environments. 18.4.1 Are These soils only in AmAzoniA? Anthrosols occur around the world, so these anthropogenic TP soils are not unique in that sense. Wherever people have occupied the land for a long time, they have modified their soils, but with varying impact and degree of intentionality. Prime examples are the anthrosols found in northern Europe, known as plaggen soils, which are the result of deliberate composting of stable waste in order to both raise the land and make it more productive. Another place where soils bear the clear signal of human action is in Meso-America where indigenous people enriched soils due to longterm habitation and made changes in the landscape by constructing terraces and creating raised beds of cultivated soils called chinampas. Elsewhere in the Americas, we know of raised beds on the Bolivian altiplano and terraces in the Andes, which are a means of water control but are also examples of active modification of soils. One can argue that chinampas and terraces are examples of landscape modification more than soils modification, but these activities go hand in hand. By creating terraces, people, in effect, manage downslope sedimentation and augment this with additional inputs such as crop waste, manure, and nightsoil. Similarly, terraces dominate densely populated areas of Asia and though often thought of as primarily a means of managing the water needed for rice cultivation, are in effect also forms of soil management. Inhabitants of many nonvolcanic Pacific islands created fertile soils in wet gardens by augmenting natural accumulations of organic debris in limestone hollows. This permitted a more productive agriculture to take place in what otherwise would be rather infertile islands. In Australia, old Aboriginal cooking hearths have resulted in more carbon in soils in places where Aboriginals lived for longer periods of time, but these are not quite the ADEs found in the Amazon. In West Africa, there is evidence of deliberate enrichment of patches of land in savannas to create forest islands with desired tree species. These are similar to forest islands of anthropogenic origin in the savanna to the south of the Amazon Basin (knows as the cerrado), which were created by Amerindians. Chemically, ADEs are unique. By virtue of their high organic matter content being stable, even recalcitrant, its pyrogenic carbon, and the high phosphorus and other chemical signatures of ADEs, their microbial complexes, and possibly the composition of the ceramics contained in TP soils especially, they are not the same in other anthrosols found around the world. An obvious question then is, why not? Are there no ADE-like soils in places such as the Congo basin or other tropical locales where natural conditions are not unlike those found in the Amazon basin and where people have lived for a long time? The answer is that we do not yet know for sure that ADE-like soils are not found elsewhere; it is a topic that needs much further research. It might be that there has been an Amazonian bias in research, and that there are similar soils elsewhere, but to date these have not been scientifically reported. Recent research is demonstrating that there may be similar soils in West Africa, but perhaps the differences in lifeways and vegetation used in an agricultural complex are big enough that in one place (the Amazon) living and farming resulted in ADEs, and in another (the Congo basin), it did not. Certainly, the inclusion or lack thereof of large herbivores, including domesticated ones (cattle) as existed and were managed in Africa, may play a role, but again, much more research on this matter needs to be undertaken. It could be that under certain conditions, ADEs could form in any number of tropical locations; the key is to figure out what those conditions are, and for that matter to be open to seeing these soils in landscapes where they are perhaps not expected. 18.5 TERRA PRETA SOILS AND AMAZONIAN PREHISTORY Amazonian prehistory has long been represented as one consisting mostly of shifting cultivators, nomadic farming, simple farmers, and the like. Open any lay publication or textbook about the Americas before Columbus and the Amazon is typically represented as relatively sparsely settled by people with relatively low levels of cultural achievement. Some maps simply portray a void and indicate only the high civilizations of the Andes (the Inca Empire) and those found in Meso-America (Aztec and Maya). These portrayals do a disservice to what is indicated (often only a fraction of the complexity and variety of cultures that thrived before European arrival), but an even greater disservice to acknowledging that people inhabited and successfully cultivated places such as in the Amazon Basin. Although Amazonia has never been as densely settled as other river valleys such as the Nile or the Yellow River, it was not a demographic void. Prehistoric Amazonians did not leave temples or structures as did many other prehistoric peoples; their legacy is their inscription of the landscape, now deciphered in the vegetative patterns and ADEs. Charles Mann, in his book 1491, provides an accessible synthesis and integration of much of the new knowledge about the lifeways of the people in the Americas before the arrival of Europeans, including a map that is much more detailed and inclusive of the varied cultures that inhabited the Western Hemisphere before 1492. This new revisionist research deconstructs the typical tropical forest trope into a more realistic depiction of what life was like in the region before the arrival of the Europeans. This new knowledge confirms that there were likely more people in the basin (56 million, as opposed to the long thought about half of that) prior to Columbus, and that their cultures were much more complex than previously thought. Observers of the region, including historical demographers, have long thought this, but neither the archaeological nor ethnographic evidence had been clear on this matter until recent work. The evidence comes from multiple sources, the existence and clear human signature of ADEs being a leading piece, but this is strongly supported by ethnohistoric, ethnographic, and ethnobotanical evidence. Long-term research with the indigenous peasantry of the Amazon as well as cultural groups such as the Kaapor, Kuikuru, and Kayap, Amerindian populations that have a cultural connection with their deep pasts, demonstrates some of the practices that have resulted in a much more anthropogenic Amazon. Severe depopulation at contact (it is estimated that over 90% of the native population of the Amazon perished as a consequence of disease and/or slavery in the colonial era) however makes this type of research difficult, as significant cultural regression took place. We know from linguistic evidence that remaining populations retreated away from the accessible bluffs deep into upland forest and savanna where they were forced to change their agricultural practices from a more sedentary form (managed fallows and fields of the type that resulted in ADEs) to what is often seen today as traditional shifting cultivation. Clear evidence has emerged from the ethnographic and ethnohistoric research by Michael Heckenberger and colleagues (in 2003 and 2007 articles) that prehistoric Amazonia consisted of large villages, on bluffs or near waterways, consisting of 25005000 people, which were highly interconnected with complex transportation and communication networks. People were sedentary and practiced long-term agriculture as part of a complex of forest and fallow management. The landscape was domesticated, and consisted of mosaics of active fields of primarily annual crops, regenerating fallows that were managed and augmented with perennials and tree crops, and regrown forests that were enriched with desired species for food, fiber, and medicinal plants. This contrasts with earlier interpretations of prehistoric Amazonian villages that were thought to have consisted of 50350 people who moved frequently as people shifted their place of living to accompany their shifting cultivation. William Bale, an anthropologist who worked with the Kaapor, views the Amazon as a cultural forest. He estimates that at least 12% of the Amazon consists of an anthropogenic forest, one where the human imprint is clear, and this is likely an underestimate. Why does he see the forest this way? As mentioned earlier, prehistoric Amazonians did not leave behind temples or pyramids, but instead deeply inscribed the landscape, the forest, with their actions. There was no steel in Amazonia prior to Europeans. So, in order to fell trees and create openings in the forest, people used a combination of stone axes and fire. Cutting tropical hardwood trees with a stone axe is a slow, inefficient, and incredibly laborious job that one preferred not to do frequently (steel axes are about 20 times faster than stone axes). This is why the evidence indicates that there was a great preference for reuse of previously cut forest patches (i.e., secondary growth) as these contained smaller trees and trees that were easier to cut. We also know from ethnographic and ethnohistorical research that Amerindians created and maintained forest trails wherever they traveled, enriching paths with desired trees and other plants, and preferentially selecting or weeding volunteer species. They practiced a form of silviculture and cultivated fallows as orchards. Over time, constant human management of the vegetation that surrounded and connected settlements changed and manipulated natural succession pathways. Even today, in areas of the Amazon with relatively thin populations, past settlements can be deciphered from the vegetative composition. Patches of higher densities of utilized species, including domesticates and semidomesticates, provide the human signature. Scientists have determined that at abandoned TP sites, the species that grow are domesticated plant species. They also found that this sets in motion a positive feedback in that people are attracted to prior sites of inhabitation as the soil has been improved and there is a concentration of useful species, and then by occupying that same landscape the soils and vegetation continue to be enriched. What has contributed significantly to a revisionist view of the Amazon beyond the clear new scientific evidence is a new way of framing the relationship between humans and the physical environment. The Amazon has long been the place in which a perspective known as environmental determinism was the dominant view of how people interacted with the physical environment. This idea held that cultural potential was limited by the physical environment, and that the Amazon rainforest, a hot and humid place with poor soils, was a challenging environment for humans to develop complex cultures in, and that any evidence there was of sophistication (as expressed, e.g., in quality pottery) was brought there by people from other places (e.g., the more temperate Andes). Accepting deeper history and greater human agency, a new perspective called historical ecology rejects environmental determinism and focuses on the human rather than the natural history of the environment, contextualizing it within historical and cultural traditions. Various scientists have engaged and developed this perspective, key among them are Clark Erickson and William Bale who state that culture is physically embedded and inscribed in the landscape as nonrandom patterning, often a palimpsest of continuous and discontinuous inhabitation by past and present people (p. 2 in their 2006 paper). The historical ecology perspective is part of a suite of theoretical approaches that emerged in the social sciences in the late twentieth century, often referred to as postmodern or poststructuralist approaches. These approaches offer and permit a much more differentiated view of the world, and are open to variation, differentiation, and nuance. Emerging from the rigid modernist era with its emphasis on generalizability, grand theory, and a rejection of traditional knowledge, the postmodern/poststructuralist framing of ideas is not so fixated on modernity and generalization, and is very open to ideas that emerge from the local, and from peoples whose voices were drowned out in the modern era. This has provided an opening for less environmentally deterministic views of the Amazon and has permitted an ability to see the human agency all around, especially in TP soils. A few other factors have also contributed to revisionist views of the Amazon. The first is that there has now been long and sustained focus on and debate about the region because of attention to the rainforest deforestation. This has brought about more scientific investigations of all sorts in the region, and an intensification of discussion about the regions people and ecosystems. Coupled with this is an increased institutional opening of the region to new archaeological research by both nationals from the relevant countries (Peru, Brazil, Bolivia, etc.) and foreign scientists. From an archaeological perspective, the region has been understudied, in part due to the challenges inherent to the preservation of material culture in tropical lowland environments, and in part, due to structural constraints on funding. The former has benefitted greatly from the development of better methods and new dating techniques for the environmental setting that have emerged in the last several decades and that permit better archaeological investigations to be conducted; the latter has improved as well, and is related to the institutional opening of the region to the broader range of archaeologists mentioned above. 18.6 TERRA PRETA SOILS AND THE FUTURE OF THE AMAZON (AND OTHER TROPICAL PLACES) The Amazon region is a contentious place, seen by most people as filled with the potential of one sort or another. Here again, we see dichotomous views. Developers would like to see an increase in production of agricultural commodities such as soybeans, as well as beef production, and continued logging of tropical hardwoods. Environmentalists would rather see a discontinuation of these activities, and continue to work toward having more land set aside in some form of protection from further development. As with many Amazonian dichotomies, in actuality, both are occurring simultaneously, as the governments that oversee Amazonian territories have responded to both pressures. They are interested in developing the resources of the Amazon in order to advance their economies, and have made it a priority that they, and not environmentalists from the Global North, set the agenda. Soybean production has expanded deep into the basin and soybean varieties are being developed to better tolerate rainforest conditions. The quest to better connect the basin with roadways, including a long sought-after road to the Pacific Ocean continue, as do other infrastructure development efforts. To many people who live and work in the basin, these are seen as positive developments. These same governments have also set aside land to be protected from development, as there is broad consensus that the Amazon rainforest provides environmental services not just locally but globally as well. Most of the protected areas permit sustainable use by local residents, including vast indigenous reservations, thereby acknowledging that people live throughout the basin and are part of its landscape. They have also worked toward enforcing existing laws regarding required conservation on private property, and have increased true protection of areas that are set-asides. All of these efforts are imperfect, have been drawn-out in execution, and vary in their relative success, but as a whole, governance of the Amazon has improved from all perspectives. The existence of ADEs has challenged conventional views of the physical environment in the conservation versus development debate, yet in much of the discussion about these matters, knowledge of ADEs has been ignored or brushed aside. Environmentalists, especially those in the Global North, continue to hold on to notions of the existence of a nonhuman nature, a notion that has its origins in the development of the original national parks in the American West. They are struggling with the idea of conserving land that is deeply inscribed (in its soils and vegetation) with prior human activity. But this requires a different way of thinking about the forest. The Amazon rainforest is still worth conserving, but the forest needs to be accepted as a cultural forest, and not envisioned as a pristine wilderness, since, as a cultural forest, it still maintains extensive biodiversity and provides critical ecosystem services. Concern has been raised regarding the emergence of revisionist perspectives of Amazonian prehistorynamely, that by acknowledging more human agency in the past, it opens up the Amazon to future unabated development. The people who hold this view are mostly those who imagine the Amazon as a place predominantly of pristine nature with little evidence of human activity, akin to what I discussed above. But there is a scalar tension here. Human activity, a form of disturbance, was in prehistory much milder and smaller in scale, functioning at the town/large village level and environs. It involved the manipulation of fields, fallows and forests, but on the whole, did not remove and replace the landscape with a completely different land cover. Today, large landholders (largeholders) degrade the forest by extracting many high-value hardwoods from their land, leaving many trees that are incidentally felled to rot. They convert the forest to pasture or soybean, some of these fields are the size of the state of Rhode Island (or more), so the scale of these disturbances is much more extensive and the functioning of these new landscapes is entirely different from what had been. The interest in sustainable agriculture based on knowledge embedded in TP soils is less important to these largeholders who operate in the global commodity political economic arena. What may be of interest to them, however, is that by incorporating elements of knowledge of TP soils and its modern derivative, biochar (discussed further below), they can contribute to global carbon sequestration effortscurrently this is something they can volunteer to do, but may ultimately be something that they are required to do as a consequence of global climate change treaties. The scientific investigation and documentation of TP soils has uncovered a form of (quite literally!) buried knowledge whose mysterious formation needs to be further uncovered as it offers possible alternative solutions for the sustainable management of soils of inherently low fertility. TP soils have embedded in them a form of carbonaromatic carbonthat has the potential to contribute to the creation of a more productive and sustainable landscape that can assist farmers in the future, especially smallholder farmers who either do not have access to artificial inputs or who choose not to use them. And much of the tropical lowlands around the world remain occupied by smallholder farmers who would benefit immensely from a more productive agriculture that uses organic inputs generated from waste that is readily available. This gets me to the topic of biochar. 18.6.1 BiochAr At the end of the 2006 World Congress of Soil Science, held in Philadelphia, Pennsylvania, USA, there was a workshop held to discuss the potential of generating TP-like soil conditioners. At the time, research on TPs was very active and there was considerable excitement generated by the potential of the ancient knowledge buried in these soils. Inspired by TP, academics and entrepreneurs came together and formed what has come to be known as the International Biochar Initiative (IBI) (http://www.biochar-international.org/). I quote from their website, This organization is a non-profit organization supporting researchers, commercial entities, policy makers, development agents, farmers and gardeners, and others committed to supporting sustainable biochar production and utilization systems. Sustainable biochar is a powerfully simple tool to fight global warming. This 2,000 year-old practice converts agricultural waste [via pyrolysis] into a soil enhancer that can hold carbon, boost food security, and discourage deforestation. Its one of the few technologies that is relatively inexpensive, widely applicable and quickly scalable. Although questions of intellectual property have been highlighted by Kawa and Ayuela-Caycedo in their 2008 paper, the IBI and its affiliated people and organizations have moved forward quickly, seizing on the inherent essence of TP soils, SOM stability as a consequence of aromatic carbon. Researchers, entrepreneurs, and farmers are trying in various ways to create biochar, an organic soil conditioner from organic wastes such as those generated in forestry (especially at sawmills), the waste in charcoal production, agricultural by-products (e.g., bagasse from sugar cane processing), slaughterhouse waste, manure, and other sources. Subjecting this waste to pyrolysis (slow, cool, lowoxygen burning; i.e., charring) results in biochar. This is essentially what Wim Sombroek, the late Dutch soil scientist who first brought scientific attention to TP soils and who spearheaded a revival in research on the topic in the 1990s, envisioned when he argued for Terra Preta Nova (TPN), new TP. Wim wanted to figure out ways of (re)creating (new) TP, and set out an agenda to do so before his untimely passing away. Johannes Lehmann, a soil scientist instrumental in research on TP soils and the IBI, has argued that it is difficult to figure out exactly how TP soils were formed in the past, as there are too many variables (inputs) that are unknown at this time, and may remain unknown. Although there remains substantial academic interest in pursuing just how TP formed in the past, many believe, cautiously, that what is already known about them is what will enable the provision of a more environmentally friendly and sustainable fertilizer based on biochar, something that is of great benefit to many smallholder farmers throughout the world, as this will improve the fertility of their land by using locally available by-products. Much research remains to be done on and with biochar, as there is great variability in its quality (of inputs and degree of pyrolysis, for example). But fundamentally, it is seen as a way of improving farmer production capacity and stemming land degradation throughout the world, even rehabilitating wastelands, as its use as a soil conditioner helps ameliorate soils not just over the short term, but over the long term as well. Another aspect about biochar that has global implications is its ability to contribute to carbon sequestration. The conversion of waste biomass into carbon via biochar has important implications for improving global carbon sequestration, a process of global importance. The reason for this is that waste biomass is highly degradable and therefore contributes to atmospheric carbon whereas biochar added to the soil captures carbon that is held in the soils and not subject to atmospheric emissions. 18.7 CONCLUSIONS A 2011 article by Janzen et al. in the flagship journal of the Soil Science Society of America outlined grand challenges for the field of soil science. Several of their themes overlap with the theme of this booksoils in the context of science-informed sustainabilityand especially this chapter. The linkage to these identified grand challenges are worth taking a moment to note. The efforts to find ways to (re)create TP soils, or at least use the buried knowledge of existing TP, especially as exemplified by biochar, can help address two of these challenges. The first, nutrients, questions whether we can preserve and enhance the fertility of soils while exporting ever bigger harvests. The use of TP-inspired biochar as a soil conditioner is a way of enhancing soil fertility in a sustainable way over the long term, and will contribute to more substantial harvests, especially for farmers most challenged to do so, small-scale farmers with limited resources. The second, recycling waste, questions how we better use soils as biogeochemical reactors, thereby avoiding contaminations and maintaining soil productivity. Again, biochar is a way of both recycling waste and sequestering carbon, processes with significant benefit to the global environment. And so, in conclusion, TP soils, the mysterious soils of the Amazon, while they continue to remain mysterious in some ways, provide a new way of thinking about the region, and also provide the potential for a more sustainable future. Achieving their full potential does necessitate confronting the political economic reality of the Amazon and of global agriculture in this era of global environmental change. This means accepting conservation of cultural forests as well as working toward development that is inclusive and respects sovereign rights and works with the environment, including ADEs and ADE derivatives such as biochar. ACKNOWLEDGMENTS I thank the many colleagues who work on TP soils and with whom I have interacted and collaborated. Earlier versions of parts of this chapter have been presented at colloquia at various colleges and universities. I acknowledge and appreciate the feedback I received at those opportunities as this helped sharpen my thinking about these soils. The writing of this manuscript was supported by the National Science Foundation (USA) while the author worked at the Foundation. Any opinion, finding, conclusions, or recommendation expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation (USA). FUTHER READING The study of TP soils is highly interdisciplinary, involving geographers, soil scientists, anthropologists, archaeologists, agronomists, and others. Much of the substance of what I discuss in this chapter is based on material published in four edited volumes on TP soils, which are included in the list below and marked with an asterisk (*). There is an increasing amount of research about these soils and their consequences being published in scientific journals, and I have included a few key pieces in the list below, along with a few classic, foundational pieces. Bale, W. and C.L. Erickson, eds. 2006. Time and Complexity in the Neotropical Lowlands: Studies in Historical Ecology. New York: Columbia University Press. Barrows, C.J. 2012. Biochar: Potential for countering land degradation and for improving agriculture. Applied Geography 34: 2128. Denevan, W.M. 1992. The pristine myth: The landscape of the Americas in 1492. Annals of the Association of American Geography 82(3): 369385. Denevan, W.M. 1996. A bluff model of riverine settlement in prehistoric Amazonia. Annals of the Association of American Geographers 86(4): 654681. Denevan, W.M. 2001. Cultivated Landscapes of Native Amazonia and the Andes. Oxford: Oxford University Press. Fraser, J., W. Teixeira, N. Falco, W. Woods, J. Lehmann, and A.B. Junqueira. 2011. Anthropogenic soils in the Central Amazon: From categories to a continuum. Area 43(3): 264273. Glaser, B. 2007. Prehistorically modified soils of Central Amazonia: A model for sustainable agriculture in the 21st century? Philosophical Transactions of the Royal Society (B) 362: 187196. Glaser, B. and J.J. Birk. 2012. State of the knowledge on the properties and genesis of anthropogenic dark earths in Central Amazonia (terra preta do ndio). Geochimica et Cosmochimica Acta 82: 3951. *Glaser, B. and W.I. Woods, eds. 2004. Amazonian Dark Earths: Explorations in Space and Time. Berlin: Springer. Heckenberger, M.J., A. Kuikuro, U.T. Kuikuro, J.C. Russell, M. Schmidt, C. Fausto, and B. Franchetto. 2003. 1492: Pristine forest or cultural parkland? Science 301: 17101714. Heckenberger, M.J., J.C. Russell, J.R. Toney, and M.J. Schmidt. 2007. The legacy of cultural landscapes in the Brazilian Amazon: Implications for biodiversity. Philosophical Transactions of the Royal Society (B) 362: 197208. International Biochar Initiative. http://www.biochar-international.org/ (last accessed January 25, 2013). Janzen, H.H., P.E. Fixen, A.J. Franzluebbers, J. Hattey, R.C. Izaurralde, Q.M. Ketterings, D.A. Lobb, and W.H. Schlesinger. 2011. Global prospects rooted in soil science. Soil Science Society of America Journal 75(1): 18. Kawa, N.C. and A. Ayuela-Caycedo. 2008. Amazonian Dark Earth: A model for sustainable agriculture of the past and present? The International Journal of Environmental, Cultural, Economic and Social Sustainability 4(3): 916. Lehmann, J. 2006. Bio-char sequestration in terrestrial ecosystemsA review. Mitigation and Adaptation Strategies for Global Change 11: 403427. *Lehmann, J., D.C. Kern, B. Glaser, and W.I. Woods eds. 2003. Amazonian Dark Earths: Origin, Properties, Management. Dordrecht: Kluwer. Lentz, D.L., ed. 2000. Imperfect Balance: Landscape Transformations in the Pre-Columbian Americas. New York: Columbia University Press. Mann, C.M. 2005. 1491: New revelations of the Americas before Columbus. New York: Alfred Knopf. Sombroek, W.G. 1966. Amazon Soils: A Reconnaissance of the Soils of the Brazilian Amazon Region. Wageningen: Centre for Agricultural Publications and Documentation. *Teixeira, W.G., D.C. Kern, B.E. Madari, H.N. Lima, and W.I. Woods, eds. 2009. As terras pretas de ndio da Amaznia: Sua caracterizao e uso deste conhecimento na criao de novas areas. Manaus: Embrapa Amaznia Ocidental. WinklerPrins, A.M.G.A., and S.P. Aldrich. 2010. Locating Amazonian dark earths: Creating an interactive GIS of known locations. Journal of Latin American Geography 9(3): 3350. *Woods, W.I., W.G. Teixeira, J. Lehmann, C. Steiner, A.M.G.A. WinklerPrins, and L. Rebellato, eds. 2009. Amazonian Dark Earths: Wim Sombroeks Vision. Dordrecht: Springer. 1 Environmental Studies, Advanced Academic Programs, Johns Hopkins University, 1717 Massachusetts Ave., N.W., Washington D.C. 20036, USA; Email: email@example.com.
The popular imagery of the Amazon
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