Agroecology

The Science Of Sustainable Agriculture, Second Edition

Miguel A Altieri

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9780813317182
• eBook ISBN: 9780429975097
• Edition: 2
• Topic: Biowissenschaften
• Subtopic: Biologie

This book incorporates new insights and concepts in the hope of helping guide agricultural students, researchers, and practitioners to a deeper understanding of the ecology of agricultural systems that will open the doors to new management options with the objectives of sustainable agriculture.

PART ONE

The Theoretical Basis of Agricultural Ecology

1

The Evolution of Agroecological Thought

Susanna B. Hecht

So in natural science, it is the composite thing, the thing as a whole which primarily concerns us, not just the materials of it, which are not found apart from the thing itself.

–Aristotle

The contemporary use of the term agroecology dates from the 1970s, but the science and the practice of agroecology are as old as the origins of agriculture. As researchers explore indigenous agricultures, which are modified relics of earlier agronomic forms, it is increasingly apparent that many locally developed agricultural systems routinely incorporate mechanisms to accommodate crops to the variability of the natural environment and to protect them from predation and competition. These mechanisms make use of regionally available renewable inputs and ecological and structural features of the agricultural field, fallows, and surrounding vegetation.

Agriculture in these situations involves managing resources other than the “target” crop. These production systems were developed to balance out environmental and economic risk and maintain the productive base of agriculture over time. While such agroecosystems can include infrastructure like terraces, trenches, and irrigation works, the decentralized, locally developed agronomic knowledge is central to the continuing performance of these production systems.

Why this agricultural heritage has been relatively unimportant in the formal agronomic sciences reflects biases that some contemporary researchers are trying to overcome. Three historical processes have done much to obscure and denigrate the agronomic knowledge that was developed by local peoples and non-western societies: (1) the destruction of the means of encoding, regulating, and transmitting agricultural practices; (2) the dramatic transformation of many non-western indigenous societies and the production systems on which they were based as a result of demographic collapse, slaving, and colonial and market processes; and (3) the rise of positivist science. As a result, there have been few opportunities for the insights developed in a more holistic agriculture to “filter up” into the formal scientific community. This difficulty is further compounded by unrecognized biases of agronomic researchers related to social factors such as class, ethnicity, culture, and gender.

Historically, agricultural management included rich symbolic and ritual systems that often served to regulate land use practices, and to encode the agrarian knowledge of non-literate peoples (Ellen 1982, Conklin 1972). The existence of agrarian cults and ritual has been documented for many societies, including those of Western Europe. Indeed, these cults were an essential focus of the Catholic Inquisition. Medieval social historians such as Ginzburg (1983) have shown how rural ceremonies were branded as witchcraft, and how such activities became the focus for intense persecution. Not surprisingly, as the post-Inquisition Spanish and Portuguese explorers set sail and European conquest spread over the globe for “God, gold, and glory,” part of their larger project included evangelical activities that often altered the symbolic and ritual bases of agriculture in non-western societies. These modifications transformed and often interfered with the generational and lateral transfer of local agronomic knowledge. This process, along with diseases, slaving, and the frequent restructuring of the agricultural base of rural communities for colonial and market purposes, often contributed to the destruction or abandonment of the “hard” technologies such as irrigation systems and especially to the impoverishment of “soft” technologies (cultivar types, cropping mixes, techniques of biological control, and soil management) of the local agricultures, which were far more dependent on cultural forms of transmission.

It is well documented how the diseases carried by explorers affected native populations. Especially in the New World, where rapid devastation of populations occurred. As much as 90 percent of the population of some areas died in less than 100 years (Denevan 1976). With them died cultures and knowledge systems. The grisly effects of epidemics characterized the earlier phases of contact, but other activities, especially slaving for New World plantations, were also to have drastic impacts on population and thus on agricultural knowledge until well into the 19th century.

Initially, local populations were the focus of slave raids, but these groups were often able to escape from bondage. The disease problems of the New World Indians also made them a less than ideal labor force. African populations, on the other hand, were accustomed to tropical conditions and were relatively resistant to “European” diseases. They could thus satisfy the burgeoning manpower needs of sugar and cotton plantations. Over two centuries more than 20 million slaves were transported from Africa to various slave plantations in the New World.

Slaving was directed at the best labor force (young adult men and women) and it resulted in the loss of this important labor force for local agriculture and the abandonment of agricultural works as people sought to avoid slavery by moving to areas distant from slavers. The disruption of knowledge systems through the export of labor, the erosion of the cultural basis of local agricultures, and the mortality associated with warfare stimulated by slaving raids was later compounded by the integration of these residual systems into mercantile and colonial networks.

The European contact with much of the non-western world was not benign and often involved the transformation of productive systems to satisfy the needs of local bureaucratic centers, mining or resource enclaves, and international commerce. This was achieved through direct coercion in some cases, reorienting or manipulating economies through the collusion of existing local elites and headmen in others, and through exchange. These processes fundamentally changed the basis of the agricultural economy. With the emergence of cash cropping and increased pressure on particular export items, rural land use strategies that had evolved over millennia to reduce agricultural risk and maintain the resource base were destabilized. Many studies have documented these effects (Watts 1983, Wolf 1982, Palmer and Parsons 1977, Wasserstrom 1982, Brokenshaw et al. 1979, Geertz 1962).

Finally, even when chroniclers and explorers made positive mention of native land use practices, it was difficult to translate these observations into a coherent, non-folkloric and socially acceptable form. The rise of the positivist method in science and the movement of western thought to atomistic and mechanistic perspectives associated with the 18th century enlightenment dramatically altered the discourse about the natural world (Merchant 1980).

This transition in epistemologies shifted the view of nature from that of an organic, living entity to one of a machine. Increasingly, this approach emphasized a language of science, a way of talking about the natural world that essentially dismissed other forms of scientific knowledge as superstitions. Indeed, from the time of Condorcet and Comte, the rise of science was equated with the triumph of reason over superstition. This position, coupled with an often derogatory view of the abilities of rural peoples generally, and colonized populations in particular, further obscured the richness of many rural knowledge systems whose content was expressed in discursive and symbolic form. Because the ecological context was misunderstood, the spatial and cultivar complexity of non-formalized agricultures was frequently reviled as disorder.

Given this history, one might ask how agroecology managed to re-emerge at all. The “rediscovery” of agroecology is an unusual example of the impact of pre-existing technologies on the sciences, where critically important advances in the understanding of nature resulted from the decision of scientists to study what farmers had already learned how to do (Kuhn 1979). Kuhn points out that in many cases, scientists succeeded in “merely validating and explaining, not in improving, techniques developed earlier.”

How the idea of agroecology re-emerged also requires the analysis of the influence of a number of intellectual currents that had relatively little to do with formal agronomy. The study of indigenous classification systems, rural development theory, nutrient cycling, and succession has little direct relation to crop science, soil science, plant pathology, and pest management as they are normally practiced. How disciplines as diverse as anthropology, economics, and ecology are reflected in the intellectual pedigree of agroecology is outlined briefly in the next sections in this chapter, but the entire volume shows the influences on agroecological approaches in far more detail.

What Is Agroecology?

The term agroecology has come to mean many things. Loosely defined, agroecology often incorporates ideas about a more environmentally and socially sensitive approach to agriculture, one that focuses not only on production, but also on the ecological sustainability of the production system. This might be called the “normative” or “prescriptive” use of the term agroecology, because it implies a number of features about society and production that go well beyond the limits of the agricultural field. At its most narrow, agroecology refers to the study of purely ecological phenomena within the crop field, such as predator/prey relations, or crop/weed competition.

The Ecological View

At the heart of agroecology is the idea that a crop field is an ecosystem in which ecological processes found in other vegetation formations such as nutrient cycling, predator/prey interactions, competition, commensalism, and successional changes also occur. Agroecology focuses on ecological relations in the field, and its purpose is to illuminate the form, dynamics, and function of these relations. Implicit in some agroecological work is the idea that by understanding these processes and relations, agroecosystems can be manipulated to produce better, with fewer negative environmental or social impacts, more sustainably, and with fewer external inputs. As a result, a number of researchers in the agricultural sciences and related fields have begun to view the agricultural field as a particular kind of ecosystem—an agroecosystem—and to formalize the analysis of the ensemble of processes and interactions in cropping systems. The underlying analytic framework owes much to systems theory and the theoretical and practical attempts at integrating the numerous factors that affect agriculture (Spedding 1975, Conway 1981a and 1981b, Gliessman 1982a, Conway 1985, Chambers 1983, Ellen 1982, Altieri 1983, Lowrance et al. 1984).

The Social Perspective

Agroecosystems have various degrees of resiliency and stability, but these are not strictly determined by biotic or environmental factors. Social factors such as a collapse in market prices or changes in land tenure can disrupt agricultural systems as decisively as drought, pest outbreak, or soil nutrient decline. On the other hand, decisions that allocate energy and material inputs can enhance the resiliency and recuperation of damaged ecosystems. Although human manipulations of ecosystems for agricultural production have often dramatically altered the structure, diversity, patterns of energy, and nutrient flux and mechanisms of population regulation within agricultural fields, these processes still operate and can be explored experimentally. The magnitude of the differences in ecological function between a natural and an agricultural ecosystem depends ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Acknowledgments
• PART ONE The Theoretical Basis of Agricultural Ecology
• PART TWO The Design of Alternative Agricultural Systems and Technologies
• PART THREE Alternative Production Systems
• PART FOUR Ecological Management of Insect Pests, Pathogens, and Weeds
• PART FIVE Looking Ahead
• Bibliography
• About the Contributors
• About the Book
• Index