William M. Denevan

Aboriginal Drained-Field Cultivation in the Americas: Pre-Columbian reclamation of wet lands was widespread in the savannas and highlands of Latin America.

The three main types of land reclamation in aboriginal America were irrigation, terracing, and drainage. Of these, drainage techniques have received the least attention, probably because they are no longer important and because the remnants are not conspicuous. Nevertheless, drained-field cultivation was widespread and was practiced in varied environments, including high-land basins, tropical savannas, and temperate flood plains. Sites ranged from seasonally waterlogged or flooded areas to permanent lakes. Ridging, mounding, and ditching were emphasized, rather than diking. Tools were simple, crops varied, and fertilization was accomplished mainly by mulching.

The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing

Pre-Columbian farmers of the Neotropical lowlands numbered an estimated 25 million by 1492, with at least 80 percent living within forest biomes. It is now well established that significant areas of Neotropical forests were cleared and burned to facilitate agricultural activities before the arrival of Europeans. Paleoecological and archaeological evidence shows that demographic pressure on forest resources—facilitated by anthropogenic burning—increased steadily throughout the Late Holocene, peaking when Europeans arrived in the late fifteenth century. The introduction of Old World diseases led to recurrent epidemics and resulted in an unprecedented population crash throughout the Neotropics. The rapid demographic collapse was mostly complete by 1650, by which time it is estimated that about 95 percent of all indigenous inhabitants of the region had perished. We review fire history records from throughout the Neotropical lowlands and report new high-resolution charcoal records and demographic estimates that together support the idea that the Neotropical lowlands went from being a net source of CO2 to the atmosphere before Columbus to a net carbon sink for several centuries following the Columbian encounter. We argue that the regrowth of Neotropical forests following the Columbian encounter led to terrestrial biospheric carbon sequestration on the order of 2 to 5 Pg C, thereby contributing to the well-documented decrease in atmospheric CO2 recorded in Antarctic ice cores from about 1500 through 1750, a trend previously attributed exclusively to decreases in solar irradiance and an increase in global volcanic activity. We conclude that the post-Columbian carbon sequestration event was a significant forcing mechanism of Little Ice Age cooling.

2 Prehistoric agricultural methods as models for sustainability

Publisher Summary This chapter presents a general view of prehistoric agroecological systems and methods (forms, functions, extent, and antiquity) and some brief case studies of agricultural collapses. The focus is on field technology, not on crops themselves. The chapter discusses the relevance of prehistoric agricultural methods to agricultural development today. It examines the forms, functions, antiquity, extent, and success of prehistoric agricultural methods. Many ancient methods have continued to the present, providing clues to former techniques, viability, and productivity. Change and innovation have been continuous. The distribution and extent of many of these methods is suggested by surviving field features, but most ancient fields have been destroyed by subsequent agriculture, other human and natural activity, or have been buried under sand and sediment. The agroecological lessons to be learned from the study of ancient fields and methods are derived from both a soft technology based on cultivation techniques and on the management of soils and pests and a hard technology based on landscape modification to improve the cultivation medium by increasing water availability, by drainage, by erosion control and by microclimatic modification.

The domestication of Amazonia before European conquest.

During the twentieth century, Amazonia was widely regarded as relatively pristine nature, little impacted by human history. This view remains popular despite mounting evidence of substantial human influence over millennial scales across the region. Here, we review the evidence of an anthropogenic Amazonia in response to claims of sparse populations across broad portions of the region. Amazonia was a major centre of crop domestication, with at least 83 native species containing populations domesticated to some degree. Plant domestication occurs in domesticated landscapes, including highly modified Amazonian dark earths (ADEs) associated with large settled populations and that may cover greater than 0.1% of the region. Populations and food production expanded rapidly within land management systems in the mid-Holocene, and complex societies expanded in resource-rich areas creating domesticated landscapes with profound impacts on local and regional ecology. ADE food production projections support estimates of at least eight million people in 1492. By this time, highly diverse regional systems had developed across Amazonia where subsistence resources were created with plant and landscape domestication, including earthworks. This review argues that the Amazonian anthrome was no less socio-culturally diverse or populous than other tropical forested areas of the world prior to European conquest.

Ancient Ridged Fields in the Region of Lake Titicaca

Minor landscape features which are apparently the result of pre-Columbian cultivation on poorly drained ter ain h v recently b en describ d in various parts of lowland South America. The most spectacular vestiges of these ancient ridged fields are in the seasonally inundated tropical savannas of the San Jorge floodplain of northern Colombia (Parsons and Bowen, 1966) and the Llanos de Mojos of northeastern Bolivia (Denevan, 1963; Denevan, 1967; Plafker, 1963). Similar fields have been traced in the Orinoco Llanos, in Surinam and near Guayaquil in Ecuador (Parsons and Denevan, 1967). They consist of parallel or irregular groupings of raised ridges of variable height, width and length: from a few inches to several feet in height, from about 10 to 70 feet in width, and up to several thousand feet in length. They are indicative of a careful and laborious reclamation of marshland for intensive tropical agriculture in areas which are considered marginal for agriculture today, or in which crop cultivation has been entirely abandoned. The reclamation of marshland for agriculture was also practised in the higher cultures of the New World in the highlands of Mexico and the Andes. The chinampa or floating garden agriculture of the Valley of Mexico is well known, and the form and patterns of dry, abandoned chinampas are remarkably similar in appearance to some of the ridged fields of South America (Coe, 1964). A few elevated crop platforms have also been observed in poorly drained parts of the Sabana de Bogota in Colombia (Eidt, 1959). But the largest area of ancient ridged fields so far discovered in the Americas is in the region of Lake Titicaca in Peru and Bolivia on level ground at 3800 and 3890 m (12,500 to 12,800 ft) above sea level. These previously undescribed features, now used mainly for pasture, are almost certainly of pre-Inca origin, and their existence helps to confirm other indications of a dense pre-Columbian Indian population in the area.

Hydraulic Agriculture in the American Tropics: Forms, Measures, and Recent Research

Publisher Summary This chapter discusses the hydraulic agriculture in the American tropics. The known indigenous alternatives to rain-fed swidden agriculture in tropical America are orchards, house gardens, mounding, terracing, playa and levee cultivation, irrigation, ditching, and raised fields. Hydraulic agriculture, in the broadest sense, can refer to any intentional manipulation of water to improve growing conditions for cultivated crops. Mounds and narrow ridges may serve to minimize upper-soil waterlogging. They also serve other functions, including soil aeration, weed control, and fertility addition. They do not survive well in the tropics, and a little is known about them, but they probably were not swidden fields. However, there are no environmental limitations to the development of agriculture, only cultural limitations. Agricultural potential is a cultural phenomenon; it is not something inherent in nature that can be measured, that exists independent of culture. At present, with available technology, agriculture can be carried out anywhere on earth. Whether it is or not in any given habitat is dependent on whether the culture involved has the necessary technology and whether or not there is a perceived need in relation to the costs involved. The current technology makes it possible to control temperature, move water, and make soil.

THE “PRISTINE MYTH” REVISITED

The genesis of my 1992 article entitled The Pristine Myth: The Landscape of the Americas in 1492 and a group of related articles was the formulation by Stanley Brunn, then editor of the Annals of the Association of American Geographers, of a special issue in recognition of the Columbian Quincentennial, that issue later being titled The Americas before and after 1492. To recruit manuscripts, the editor appointed a committee consisting of Karl Butzer, B. L. Turner II, Brian Harley, and myself. Ultimately Butzer became the guest editor. The authors of the special issue were under tight time constraints. They conceived the contents in mid-1991, drafted manuscripts by early 1992, and revised them in the spring. The association had scheduled publication for a September date but wanted the issue available for the 27th International Geographical Congress in Washington, D.C. in August. Thus publication was actually in early August--one of the fastest Annals assembled in recent times. This was despite Harleys intervening death after he had drafted a long and rough article with dozens of illustrations. Butzer reduced this to manageable size and coherence in addition to writing his own two-and-one-half articles and editing everything else in the issue. Congress attendees received free copies, so that issue received a greater distribution than usual. I chose to write on the pristine myth, given my long awareness of pre-1492 human impacts, reflecting my own Berkeley influences from Carl Sauer, Erhard Rostlund, and James Parsons as well as my own research, plus my emerging belief that a pristine myth does indeed exist. Certainly I was motivated when, in Meriter Hospital for surgery in Madison in the summer of 1991, I was given Kirkpatrick Sales 1990 best seller The Conquest of Paradise. A major point of the book is that the colonial Europeans transformed nature in the Americas, whereas the Indian impact had been benign or nonexistent. I thought, loaded with morphine, Such innocence! The expression pristine myth is mine, as far as I am aware. I do not recall how I came up with it. Certainly this catchy title phrase is a key to the widespread attention the article has received. However, the article does not contain anything new; it is a synthesis of the work of numerous people, many of whom I cited. I also presented the term humanized landscape, which I took from a 1979 article by Butzer: The landscape had been humanized by the first Americans (p. 148; also see Butzer 1990,48). Wilbur Zelinsky had used the term earlier: In The Cultural Geography of the United States he wrote that the United States was a partially humanized land. ... The territory entered by explorer and homesteader was not covered by the forest primaeval but had already been grossly modified by aboriginal hunting, burning, forestry, and planting (1973,16). In the Pristine Myth article I maintained that by the time the first Europeans arrived in the New World its environment had been modified to varying degrees in most places by the settlement, subsistence, burning, and other activities of Native Americans and that this has not been acknowledged by most of the educated public or by many scholars, except, of course, for the densely populated areas of the Andes, Central Mexico, and Central America. In this essay I briefly revisit my 1992 article and present some of the many responses to it and to related studies and statements, with a partial bibliography of a large literature. RESPONSES The Pristine Myth quickly received considerable comment and controversy in and out of academia, in numerous newspapers including the New York Times, also in Newsweek, and there were several radio interviews. However, at least eight other articles on the topic also appeared in 1992, including those by the geographers Martyn Bowden on invented tradition (1992a), Turner and Butzer in Environment (1992), and Jared Diamond in The Third Chimpanzee (1992); by the anthropologist Steven Simms on Wilderness as a Human Landscape (1992); and by the biologists Arturo Gomez-Pompa and Andrea Kaus in BioScience (1992; see also Gastang 1992; Gomez-Pompa 1992). …

Pre-Hispanic Agricultural Fields in the Andean Region

The twenty-six papers in this collection represent the Proceedings of the 45th International Congress of Americanists at Bogota in 1985. They are grouped into topics and regions as follows: Agricultural terracing in the 0000 valley, Peru (8)

Semi-Intensive Pre-European Cultivation and the Origins of Anthropogenic Dark Earths in Amazonia

Anthropogenic dark earths are widespread in the uplands (terra firme) of Amazonia, in patches covering a hectare or less up to several hundred hectares. The blacker form (terra preta) seems to have developed from preEuropean village middens consisting of ash and charcoal from kitchen fires, cultural debris, feces, human and animal bones, and house/garden waste (Woods and McCann 1999). The lighter, dark brown form (terra mulata), which is much more extensive, is believed by some soil scientists (Sombroek 1966:175; Glaser et al. 2001a), archaeologists (Herrera et al. 1992; Petersen et al. 2001), botanists (Prance and Schubart 1978), and geographers (Denevan 1998; Woods and McCann 1999) to be the product of intensive cultivation practices (Fig. 10.1). Others, however, such as Smith (1980) and Eden et al. (1984), rejected an agricultural origin because of the depth of dark earth soils. Smith argued for midden origins, and he saw soil color and depth as being functions of length of village-site duration. In 1980 he was apparently unaware of the extent of terra mulata that contains little or no midden material.

Estimating Amazonian Indian Numbers in 1492

Since 1965 I have made several attempts to estimate the native population of Amazonia in 1492. My original method was to determine rough habitat densities, which project to totals for Greater Amazonia of from 5.1 to 6.8 million. I have rejected this method, given that the denser populations were mostly clustered rather than evenly dispersed. I nevertheless still believe that a total of at least five to six million is reasonable and as many as 10 million when dense terra preta populations are considered.