Miguel A. Altieri

The ecological role of biodiversity in agroecosystems

Increasingly research suggests that the level of internal regulation of function in agroecosystems is largely dependent on the level of plant and animal biodiversity present. In agroecosystems, biodiversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate and local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals. In this paper the role of biodiversity in securing crop protection and soil fertility is explored in detail. It is argued that because biodiversity mediated renewal processes and ecological services are largely biological, their persistence depends upon the maintenance of biological integrity and diversity in agroecosystems. Various options of agroecosystem management and design that enhance functional biodiversity in crop fields are described. ©1999 Elsevier Science B.V. All rights reserved.

Agroecology: the science of natural resource management for poor farmers in marginal environments

Throughout the developing world, resource-poor farmers (about 1.4 billion people) located in risk-prone, marginal environments, remain untouched by modern agricultural technology. A new approach to natural resource management must be developed so that new management systems can be tailored and adapted in a site-specific way to highly variable and diverse farm conditions typical of resource-poor farmers. Agroecology provides the scientific basis to address the production by a biodiverse agroecosystem able to sponsor its own functioning. The latest advances in agroecological research are reviewed in order to better define elements of a research agenda in natural resource management that is compatible with the needs and aspirations of peasants. Obviously, a relevant research agenda setting should involve the full participation of farmers with other institutions serving a facilitating role. The implementation of the agenda will also imply major institutional and policy changes.

Vegetation management and biological control in agroecosystems

Abstract The application of diversity/stability considerations in theoretical ecology has led to the emergence of testable hypotheses with implications for biological control and agroecosystem management. The object of applied research in this area has been to achiece predictably stable pest populations (below an economic threshold level) in crop systems. The exacerbation of most insect-pest problems has been associated with increases in crop monocultures at the expense of the natural vegetation, thereby decreasing local habitat diversity. This can seriously affect the abundance and efficiency of natural enemies, which depend on habitat complexity for sources of alternate prey/hosts, pollen and nectar, shelter, nesting and overwintering sites. Plant diversification of agroecosystems can result in increased environmental opportunities for natural enemies and, consequently, improved biological pest control. Agronomically, there are several ways to design plsnt-diverse cropping systems. One way is by manipulating the vegetation of field margins, and managing the species composition and density of plants in ditchbanks, hedgerows, windbreaks and other types of shelter belts. Within-field plant diversity can be manipulated by designing polycultures of various temporal and spatial crop arrangements. The effects of some of these systems on the dynamics of insect populations are discussed, as well as the effects of cover-crop management on pest insects in orchards. Another way to enrich the vegetational structure of cropping systems is through weed management. Weed diversity in the form of weed borders, alternate rows, or by providing weeds in certain periods of the crop growth can have a major impact on insect dynamics.

Agroecology: The Ecology of Food Systems

ABSTRACT We present a compelling rationale for defining agroecology as the ecology of food systems. Our purpose is to provide a framework that will guide research, education, and action in the multiple and interacting facets of an increasingly complex global agriculture and food system. To accomplish such goals, it is essential to build bridges and connections among and beyond our disciplines in production agriculture, as well as beyond the farm gate into the rural landscape and community. Fields of sociology, anthropology, environmental sciences, ethics, and economics are crucial to the mix. They provide additional vantage points from which we can view the food system anew, as well as insights on how to establish valuation criteria beyond neoclassical economics. Examples from Mexico, California, and the Nordic Region are used to illustrate the successful implementation of this educational strategy in universities. Design of individual farms using principles of ecology is expanded to the levels of landscape, community, and bioregion, with emphasis on uniqueness of place and the people and other species that inhabit that place. We conclude that defining agroecology as the ecology of food systems will foster the development of broader interdisciplinary research teams and attractive systems-based courses for tomorrows best students. In contrast to the narrow focus on crop-soil interactions, this definition will help us raise higher-level research questions whose solutions will advance the development of a sustainable agriculture and food system.

The agroecological revolution in Latin America: rescuing nature, ensuring food sovereignty and empowering peasants

This paper provides an overview of what we call ‘agroecological revolution’ in Latin America. As the expansion of agroexports and biofuels continues unfolding in Latin America and warming the planet, the concepts of food sovereignty and agroecology-based agricultural production gain increasing attention. New approaches and technologies involving the application of blended agroecological science and indigenous knowledge systems are being spearheaded by a significant number of peasants, NGOs and some government and academic institutions, and they are proving to enhance food security while conserving natural resources, and empowering local, regional and national peasant organizations and movements. An assessment of various grassroots initiatives in Latin America reveals that the application of the agroecological paradigm can bring significant environmental, economic and political benefits to small farmers and rural communities as well as urban populations in the region. The trajectory of the agroecological movements in Brazil, the Andean region, Mexico, Central America and Cuba and their potential to promote broad-based and sustainable agrarian and social change is briefly presented and examined. We argue that an emerging threefold ‘agroecological revolution’, namely, epistemological, technical and social, is creating new and unexpected changes directed at restoring local self-reliance, conserving and regenerating natural resource agrobiodiversity, producing healthy foods with low inputs, and empowering peasant organizations. These changes directly challenge neoliberal modernization policies based on agribusiness and agroexports while opening new political roads for Latin American agrarian societies.

In situ conservation of crop genetic resources through maintenance of traditional farming systems.

A strategy is suggested for in situ conservation of crop genetic resources whereby conservation efforts are linked to rural development projects in Third World countries. We describe development projects that emphasize preservation of traditional farming systems and succeed in sustaining production by relying on the maintenance of biological and genetic diversity in these systems. Basing agricultural development efforts on indigenous knowledge, technology, and social organization can provide important guidelines for the design of cropping systems that allow lowincome farmers to produce subsistence and cash crops without dependence on external inputs and seed supplies. By incorporating landraces and wild relatives of crops into these cropping systems, major achievements in the conservation of crop genetic resources can be obtained.

Linking ecologists and traditional farmers in the search for sustainable agriculture

For centuries, traditional farmers have developed diverse and locally adapted agricultural systems, managing them with ingenious practices that often result in both community food security and the conservation of agrobiodiversity. This strategy of minimizing risk stabilizes yields, promotes dietary diversity, and maximizes returns using low levels of technology and limited resources. These microcosms of agricultural heritage still cover no less than 10 million ha worldwide, providing cultural and ecological services not only to rural inhabitants, but to mankind generally. These services include the preservation of traditional farming knowledge, local crop and animal varieties, and native forms of sociocultural organization. By studying these systems, ecologists can enhance their knowledge of the dynamics of complex systems, especially the relationship between biodiversity and ecosystem function and practical principles for the design of more sustainable agroecosystems appropriate to small farmers. Novel a...

Soil fertility management and insect pests: harmonizing soil and plant health in agroecosystems

Cultural methods such as crop fertilization can affect susceptibility of plants to insect pests by altering plant tissue nutrient levels. Research shows that the ability of a crop plant to resist or tolerate insect pests and diseases is tied to optimal physical, chemical and mainly biological properties of soils. Soils with high organic matter and active soil biology generally exhibit good soil fertility. Crops grown in such soils generally exhibit lower abundance of several insect herbivores, reductions that may be attributed to a lower nitrogen content in organically farmed crops. On the other hand, farming practices, such as excessive use of inorganic fertilizers, can cause nutrient imbalances and lower pest resistance. More studies comparing pest populations on plants treated with synthetic versus organic fertilizers are needed. Understanding the underlying effects of why organic fertilization appears to improve plant health may lead us to new and better integrated pest management and integrated soil fertility management designs.

Agroecologically efficient agricultural systems for smallholder farmers: contributions to food sovereignty

The realization of the contribution of peasant agriculture to food security in the midst of scenarios of climate change, economic and energy crisis, led to the concepts of food sovereignty and agroecologically based production systems to gain much attention in the developing world in the last two decades. New approaches and technologies involving application of blended modern agricultural science and indigenous knowledge systems and spearheaded by thousands of farmers, NGOs, and some government and academic institutions are proving to enhance food security while conserving agrobiodiversity soil and water resources conservation throughout hundreds of rural communities in the developing world. Case studies from Cuba, Brazil, Philippines, and Africa are presented to demonstrate how the agroecological development paradigm based on the revitalization of small farms which emphasizes diversity, synergy, recycling and integration, and social processes that value community participation and empowerment, proves to be perhaps one of the only viable options to meet present and future food needs. Given the present and predicted near future climate, energy and economic scenarios, agroecology has emerged as one of the most robust pathways towards designing biodiverse, productive, and resilient agroecosystems available today.

Agroecology, Small Farms and Food Sovereignty.

Global forces are challenging the ability of developing countries to feed themselves. A number of countries have organized their economies around a competitive export-oriented agricultural sector, based mainly on monocultures. It may be argued that agricultural exports of crops such as soybeans from Brazil make significant contributions to the national economies by bringing in hard currency that can be used to purchase other goods from abroad. However, this type of industrial agriculture also brings a variety of economic, environmental, and social problems, including negative impacts on public health, ecosystem integrity, food quality, and in many cases disruption of traditional rural livelihoods, while accelerating indebtedness among thousands of farmers.This article can also be found at the Monthly Review website, where most recent articles are published in full.Click here to purchase a PDF version of this article at the Monthly Review website.