Amazonian Dark Earths: Wim Sombroek’s Vision

William I. Woods (Editor), Wenceslau G. Teixeira (Editor), Johannes Lehmann (Editor), Christoph Steiner (Editor), Antoinette M.G.A. WinklerPrins (Editor), Lilian Rebellato (Editor). 2009. Amazonian Dark Earths: Wim Sombroek’s Vision. Springer; 1st edition (December 1, 2008). 504 pages. listing [here].

Review by Mike Dubrasich

A landmark book has been published on terra preta, Amazonian dark earths, the carbon-rich soils developed by ancient civilizations in what was once thought to be a pristine wilderness. Dedicated to Dutch soil scientist Wim Sombroek (1934-2003) who was the first modern investigator of terra preta, Amazonian Dark Earths: Wim Sombroek’s Vision is a compilation of the latest, cutting-edge studies in this fascinating and important multi-disciplinary field.

Amazonian soils are predominantly laterites [here], deeply weathered red clays lacking in most soil nutrients. Millions of years of rainfall have leached out everything but iron (hence the red color), silica, and aluminum. Essential plant nutrients such as calcium, phosphorus, and potassium are nearly missing. Amazon vegetation subsists on itself, the thin humus of decaying plant matter being the only source of key metallic oxides.

Except where there is terra preta, or it’s close cousin terra mulata. Terra preta is deep, rich, fertile, black soil that occurs in patches on bluffs along the Amazon and its tributaries. Terra preta is filled with charcoal, ash, mulch, bones, and pottery shards! It is potting soil made from organic matter transported to the sites in pots! These anomalous soils are anthropogenic: people made them.

[Dr. William] Denevan (2001:116–119) has argued that in pre-Columbian times the use of stone axes made long-fallow shifting cultivation very inefficient, and as result probably uncommon until the European introduction of metal axes. Previously, soil fertility must have been maintained and improved by frequent composting, mulching, and in-field burning, making semi-permanent cultivation possible with only brief fallowing. Over time these activities could have produced fertile, self-sustaining dark earths.

Dark earths may occupy 0.1% to 0.3%, or 6,000 to 18,000 km2, of forested lowland Amazonia (Sombroek and Carvalho 2002:130). Because their densities vary greatly within subregions and almost no systematic survey has been accomplished within Amazonia, variations in density projections of an order of magnitude are to be expected. The dark earths occur in a variety of climatic, geologic, and topographic situations, both along river bluffs and in the interior, with depths sometimes exceeding 2.0 m. Individual patches range from 1 ha or so to several hundred hectares. — from Chapter 1, Amazonian Dark Earths: The First Century of Reports by William I. Woods and William M. Denevan

Rather than a pristine, untrammeled, unoccupied wilderness, Amazonia has been home to people for thousands of years. The indigenous residents were agriculturalists who modified soils in order to grow corn (maize), squash, beans, fruiting palms, gourds, pineapples, cotton, arrowroot, and many other cultivated fruits, nuts, tubers, and fibers.

Terra mulata is brownish soil that generally surrounds patches of terra preta. It is not quite as rich and has fewer artifacts, and is even more widespread than terra preta. In theory, terra mulata is the accidentally improved soil adjacent to the deliberately improved soils, or else it is terra preta in the making. In either case, anthropogenically altered soils are in strong contrast to the unaltered laterites, and cover a combined area the size of France.

One of the key elements of terra preta is charcoal, lately termed “biochar”.

Vegetation actively withdraws carbon from the atmosphere and stores it as organic matter. Biochar is created when organic matter is heated without oxygen and it contains twice the carbon content of ordinary biomass (Lehmann 2007). Biochar is much more resistant to decay and can store carbon for centennial timescales (Lehmann et al. 2006). The addition of biochar to the soil was part of the creation of ADE [Amazon dark earths] (Neves et al. 2003). This has lead some to speculate on the viability of a biochar carbon sequestration industry which would reduce atmospheric greenhouse gases (Marris 2006; Sombroek et al. 2002) and improve soil fertility (Lehmann et al. 2003; Glaser and Woods 2004). — from Chapter 14, Locating Amazonian Dark Earths (ADE) Using Satellite Remote Sensing – A Possible Approach by J Thayn, KP Price, and WI Woods.

Biochar is touted as a “solution” to the global warming “problem.” I demure. But biochar is definitely a valuable soil amendment because carbon binds to and stores the metallic oxide nutrients essential to plant growth. The addition of charcoal as well as organic detritus helped to create and sustain terra preta over centuries.

Amazonian Dark Earths: Wim Sombroek’s Vision is a wonderful account of the history and science of anthropogenic soils. The book is as rich as terra preta in literary as well as scientific writing.

An introductory essay by Charles C. Mann, author of 1491: New Revelations of the Americas Before Columbus [here], is a mini-biography of Wim Sombroek. Sombroek’s Amazon Soils: A Reconnaissance of the Soils of the Brazilian Amazon Region (1966) first drew the attention of soil scientists to terra preta.

Found in patches along almost all of the major rivers in the Amazon basin, Amazonian Dark Earth is, unlike typical tropical soils, rich with phosphorus, nitrogen, zinc, and magnesium. More important, it is full of carbon – as much as 70 times the level of neighboring soils—in the form of “bio-char,” a charcoal-like residue created when organic matter is burned at a low temperature.

As far back as the 1960s, Wim had wondered whether scientists could reconstruct the techniques by which Indians had made terra preta in the past. If so, he now argued, contemporary tropical farmers might create their own terra preta — terra preta nova, as he dubbed it — to help forestall soil degradation. Because soil degradation is an enormous limiting factor in tropical agriculture, terra preta nova could not only boost yields but also reduce the amount of tropical forest that had to be cleared for farms. Much as the Green Revolution dramatically improved the developing world’s crops, resilient terra preta nova could unleash a “black revolution” for the developing world’s soil. — from the introductory A Few Words About Wim Sombroek by Charles C. Mann

The other chapters of Amazonian Dark Earths: Wim Sombroek’s Vision are written by a who’s who of top soil scientists, landscape geographers, and ethno-ecologists from North and South America:

1 Amazonian Dark Earths: The First Century of Reports by WI Woods and WM Denevan

2 Pre-Columbian Settlement Dynamics in the Central Amazon by L Rebellato, WI Woods, and EG Neves

3 Steps Towards an Ecology of Landscape: The Pedostratigraphy of Anthropogenic Dark Earths by M Arroyo-Kalin

4 Phytoliths and Terra Preta: The Hatahara Site Example by SR Bozarth, K Price, WI Woods, EG Neves, and L Rebellato

5 Anthropogenic Dark Earths of the Central Amazon Region: Remarks on Their Evolution and Polygenetic Composition by M Arroyo-Kalin, EG Neves, and WI Woods

6 An Assessment of the Cultural Practices Behind the Formation (or Not) of Anthropogenic Dark Earth in Marajó Island Archaeological Sites by DP Schaan, DC Kern, and FJL Frazão

7 Kayapó Savanna Management: Fire, Soils, and Forest Islands in a Threatened Biome by SB Hecht

8 Amerindian Anthrosols: Amazonian Dark Earth Formation in the Upper Xingu by MJ Schmidt and MJ Heckenberger

9 Indigenous Knowledge About Terra Preta Formation by C Steiner, WG Teixeira, WI Woods, and W Zech

10 Sweep and Char and the Creation of Amazonian Dark Earths in Homegardens by AMGA Winklerprins

11 Pedology, Fertility, and Biology of Central Amazonian Dark Earths by NPS Falcão, CR Clement, SM Tsai, and NB Comerford

12 Historical Ecology and Dark Earths in Whitewater and Blackwater Landscapes: Comparing the Middle Madeira and Lower Negro Rivers by J Fraser, T Cardoso, A Junqueira, NPS Falcão, and CR Clement

13 Amazonian Dark Earths in Africa? by J Fairhead and M Leach

14 Locating Amazonian Dark Earths (ADE) Using Satellite Remote Sensing – A Possible Approach by J Thayn, K Price, and WI Woods

15 The Microbial World of Terra Preta by SM Tsai, B O’Neill, FS Cannavan, D Saito, NPS Falcão, D Kern, J Grossman, and J Thies

16 Microbial Response to Charcoal Amendments and Fertilization of a Highly Weathered Tropical Soil by JJ Birk, C Steiner, WC Teixeira, W Zech, and B Glaser

17 Effects of Charcoal as Slow Release Nutrient Carrier on N-P-K Dynamics and Soil Microbial Population: Pot Experiments with Ferralsol Substrate by C Steiner, M Garcia, and W Zech

18 Terra Preta Nova: The Dream of Wim Sombroek by DC Kern, M de LP Ruivo, and FJL Frazão

19 Microbial Population and Biodiversity in Amazonian Dark Earth Soils by M de LP Ruivo, CB do Amarante, M de LS Oliveira, ICM Muniz, and DAM dos Santos

20 Spectroscopic Characterization of Humic Acids Isolated from Amazonian Dark Earth Soils (Terra Preta de Índio) by TJF Cunha, EH Novotny, BE Madari, L Martin-Neto, MO de O Rezende, LP Canellas, and V de M Benites

21 Solid-State 13C Nuclear Magnetic Resonance Characterization of Humic Acids Extracted from Amazonian Dark Earths (Terra Preta de Índio) by EH Novotny, TJ Bonagamba, ER de Azevedo, and MHB Hayes

22 Opening the Black Box: Deciphering Carbon and Nutrient Flows in Terra Preta by G van Hofwegen, TW Kuyper, E Hoffland, JA van den Broek, and GA Becx

23 Charcoal Making in the Brazilian Amazon: Economic Aspects of Production and Carbon Conversion Efficiencies of Kilns by SN Swami, C Steiner, WG Teixeira, and J Lehmann

24 The Effect of Charcoal in Banana (Musa Sp.) Planting Holes – An On-Farm Study in Central Amazonia, Brazil by C Steiner, WG Teixeira, and W Zech

25 Characterization of Char for Agricultural Use in the Soils of the Southeastern United States by JW Gaskin, KC Das, AS Tasistro, L Sonon, K Harris, and B Hawkins

26 Black Carbon (Biochar) in Rice-Based Systems: Characteristics and Opportunities by SM Haefele, C Knoblauch, M Gummert, Y Konboon, and S Koyama

27 City to Soil: Returning Organics to Agriculture: A Circle of Sustainability by G Gillespie

28 Terra Preta Nova – Where to from Here? J Lehmann

William Woods, lead editor and co-author of Chapters 1, 2, 4, 5, 9, and 14, is Professor in the Department of Geography, University of Kansas and the former Director of the Environmental Studies Program there, and author of Population nucleation, intensive agriculture, and environmental degradation: The Cahokia example [here] among other works.

William Deneven, co-author of Chapter 1, is professor emeritus of Geography at the University of Wisconsin-Madison and author of Cultivated Landscapes of Native Amazonia and the Andes [here] among other landmark works. Bill Denevan is the “godfather” of historical landscape geography.

Susanna Hecht, author of Chapter 7, is Associate Professor in the Graduate School of Architecture and Urban Planning at UCLA. She is the author of The Fate of the Forest: Developers, Destroyers and Defenders of the Amazon and an essay we featured [here] among other works. Her chapter on the Kayapó savannas is particularly interesting because they were created and maintained by anthropogenic fire, much as were many of our N. American woodlands.

[Native populations] depended on resource islands that recent research suggests were largely anthropogenic (Balée 1994; Cormier 2006; Posey 2003; Rival 2003). These management activities including maintenance of resource areas, through clearing, planting (intentionally or otherwise) ritual activities, transfer of germplasm, extraction and manipulation of resources such as casual pruning and weeding of resources islands and above all burning (Verswijver 1996). …

Studies of human intervention in savanna ecosystems in the New World are useful because they reveal the vast extension of human action on landscape. Research on native burning patterns report that cool, frequent burning by natives is an important feature of their savanna landscape management, and many areas are burned on annual and up to 3 year cycles generating low biomass burns (Andersen et al. 2003; Batalha and Martins 2007; Burbridge et al. 2004; Martins 1995; Mayle et al. 2007; McDaniel et al. 2005; Mistry et al. 2005; Ribeiro 2005; Rodriguez 2007). Burning is one of the most powerful management tools available to native peoples, it is the great transformer and unsurprisingly it is widely used for a range of purposes. …

The Kayapó burn the Cerrado systems in many complex ways, although the intentionality of the burning in some cases may be open to speculation. The Kayapó burn throughout the dry season, the burning is usually done early in the day. The spatial mosaic of the burning is very uneven, creating a pattern of burn history of different extent, intensity and age and types of ash depending on the burn temperature. As has been noted elsewhere, burning is a constant feature of Kayapó resource management and throughout the dry season one is in a kind of smoldering landscape (Hecht 2003, 2005).

Fire is a dialectical entity: it is the transformer of the wild into the tame, the “raw into the cooked”, to quote Levi Strauss, as it takes forests and turns them to gardens and savannas, but it can also become wild and devour villages and fields. The duality that inheres in fire is not itself that unusual as it is after all a tamed primordial force, but its relevance for our Kayapó situation is that fire is both a destroyer of forest in the cerrado and a creator and maintainer of specialized forests of palms, successional forests/ orchards, bamboo forests (tabocal) and campo woodland islands (the Apêtê). — from Chapter 7, Kayapó Savanna Management: Fire, Soils, and Forest Islands in a Threatened Biome by SB Hecht.

Michael Heckenberger, co-author of Chapter 8, is Associate Professor of Anthropology, University of Florida. He is co-author of Amazonia 1492: Pristine Forest or Cultural Parkland? 2003. Science Vol 301: 1710-1714 and The legacy of cultural landscapes in the Brazilian Amazon: implications for biodiversity [here] among other works.

Essays or papers by other authors including Christoph Steiner, University of Georgia, and Johannes Lehmann, Cornell University, may soon be appearing at W.I.S.E.

Amazonian Dark Earths: Wim Sombroek’s Vision is a landmark book. It relates the latest findings in landscape history, indigenous practices, soil development, soil chemistry, anthropology, and archaeology, and the implications of those to modern social and land stewardship issues.

If the book has a defect, it is the price. That is not the authors’ fault; they are uniformly interested in conveying their findings to a larger audience. The publisher, Springer, has put up a barrier to the wider dissemination of cutting-edge science by setting the price so high ($183). They need to find another business proposition that works in the Digital Age. Maybe publish it as a Kindle Book [here] for a tenth of the cellulose and glue price?????

Otherwise people might be tempted to pirate copies to their friends, and nobody involved in the production of the book gets paid in that unfortunate happenstance.

However you obtain it (check it out from your local university library perhaps?), Amazonian Dark Earths: Wim Sombroek’s Vision is a must read for students and scholars of landscape geography.

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