A Question of Diversity
21 Dec 09 - Miguel A. Altieri - Sloweek
Biodiversity in agriculture or agro-biodiversity refers to all crops and animal breeds, their wild relatives, and other species such as pollinators, symbionts, natural enemies of pests, soil fauna, etc that co-exist and interact within croplands and/or their surrounding environments. It includes populations of locally adapted crop varieties and animal races as well as wild and weedy relatives from which the entire range of the domestic crops used in world agriculture is derived.
Agro-biodiversity components perform ecosystem functions and deliver services that sustain the resources and ecological processes upon which agriculture depends. Ecosystem services beyond production of food, fiber, fuel, and income include recycling of nutrients, control of local microclimate, regulation of local hydrological processes, pollination, regulation via biological control of the abundance of undesirable organisms, detoxification of noxious chemicals, etc. All renewal processes and ecosystem services performed by agro-biodiversity are largely biological, therefore their persistence depends upon maintenance of biological diversity and the ecological integrity of agricultural systems.
When these natural services are lost due to biological simplification due to intensification of agriculture, the economic and environmental costs can be quite significant. In industrial agriculture the burdens include a reduction in crop production due to enhanced pests that become resistant to pesticides or due to elimination of their enemies, decreases in pollinators, and other services such as the capacity of soils to sequester carbon dioxide, etc. In general there is an overall reduction in the overall quality of life due to soil, water, and food contamination with accumulation of pesticide and/or nitrate residues, on less dietary diversity associated with monocultures.
The net result of biodiversity simplification is an industrial agricultural monoculture that requires constant human intervention in the form of mechanization and agrochemicals that in addition to posing environmental damage they heavily depend on energy subsidies and produce copious amounts of greenhouse gases.
Modern agriculture implies the simplification of the structure of the environment over vast areas, replacing nature's diversity with a small number of cultivated plants and domesticated animals. In fact, the world's agricultural landscapes are planted mostly with some 12 species of grain crops, 23 vegetable crop species, and about 35 fruit and nut crop species; that is no more than 70 plant species spread over approximately 1,440 million ha. of presently cultivated land in the world, a sharp contrast with the diversity of plant species found within one ha. of a tropical rain forest which typically contains over 100 species of trees .
Genetically, modern agriculture is shockingly dependent on a handful of varieties for its major crops. For example, in the
, 60 to 70% of the total bean acreage is planted with two to three beans varieties, 72% of the potato acreage with four varieties and 53% with three cotton varieties. Researchers have repeatedly warned about the extreme vulnerability associated with this genetic uniformity. U.S.
A growing number of scientists, farmers, and the general public fear for the long-term sustainability of such highly input-dependent and ecologically simplified food production systems. These concerns have gained renewed attention with the expansion of transgenic crops and agro-fuel plantations which by 2008 covered more than 140 million hectares leading to further large-scale landscape homogenization which will exacerbate the ecological problems already associated with industrial agriculture.
Industrial agriculture, monocultures and Third World small farmers
Unquestioned expansion of these industrial models into developing countries is not desirable especially when consequences of promoting monocultures results in serious social and environmental problems as exemplified by the Green Revolution launched in the developing world in the 60s and 70s and now promoted in Africa by the AGRA program. These people assume that progress and achieving development in traditional agriculture inevitably requires the replacement of local crop varieties for improved ones, and that the economic and technological integration of traditional farming systems into the global system is a positive step that enables increased production, income and commonly well being. But as evinced by the Green Revolution integration brought in addition several negative impacts:
• The Green Revolution involved the promotion of a package that included modern varieties (MVs), fertilizer and irrigation, marginalizing a great number of resource-poor farmers who could not afford the technology.
• In areas where farmers adopted the package stimulated by government extension and credit programs, the spread of MVs greatly increased the use of pesticides, often with serious health and environmental consequences.
• Enhanced uniformity caused by sowing large areas to a few MVs increased risk for farmers. Genetically uniform crops proved more susceptible to pests and diseases, and also improved varieties did not perform well in marginal environments where the poor live.
• Diversity is an important nutritional resource of poor communities, but the spread of MVs was accompanied by a simplification of traditional agro-ecosystems and a trend toward monoculture which affected dietary diversity thus raising considerable nutritional concerns.
• The replacement of folk varieties also represents a loss of cultural diversity, as many varieties are integral to religious or community ceremonies. Given this, several authors have argued that the conservation and management of agrobiodiversity may not be possible without the preservation of cultural diversity.
Concerns have been raised about weather the introduction of transgenic crops may replicate or further aggravate the effects of MVs on the genetic diversity of landraces and wild relatives in areas of crop origin and diversification and therefore affect the cultural thread of communities. The debate was prompted by Nature’s controversial article reporting the presence of introgressed transgenic DNA constructs in native maize landraces grown in remote mountains in
. Although there is a high probability that the introduction of transgenic crops will further accelerate the loss of genetic diversity and of indigenous knowledge and culture, through mechanisms similar to those of the Green Revolution, there are some fundamental differences in the magnitude of the impacts. The Green Revolution increased the rate at which modern varieties replaced folk varieties, without necessarily changing the genetic integrity of local varieties. Genetic erosion involves a loss of local varieties but it can be slowed and even reversed through in-situ conservation efforts which conserve not only landraces and wild-weedy relatives, but also agro-ecological and cultural relationships of crop evolution and management in specific localities. Examples of successful in-situ conservation have been widely documented. Oaxaca, Mexico
There is strength in the agricultural diversity of many African, Latin American and Asian countries, where traditional and small farmers have historically used mixed farming systems with high degrees of plant diversity in the form of polycultures, agroforestry and animal integration patterns, providing a strong ecological foundation to sustain small farm productivity and to design agroecological models that provide food security for thousands of rural and urban poor. In
Latin America small farmers who farm less than 30 % of the total cultivated land account for approximately 41% of the agricultural output for domestic consumption, including 51% of the maize, 77% of the beans, and 61% of the potatoes consumed at a regional level. In Africa the majority of farmers, many of them women, are smallholders who practice “low-resource” agriculture producing the majority of grain; almost all root, tuber and plantain crops, and the majority of legumes. In Asia, only a few of the more than 200 million rice farmers farm more than 2 ha of rice. In alone there are probably 75 million rice farmers who still practice farming methods similar to those used more than one thousand years ago. Local cultivars, grown mostly on upland ecosystems and/or under rain-fed conditions, make up the bulk of the rice produced by Asian small farmers. China
Biodiversity and organic agriculture.
Extensive research shows that organic agriculture has positive impacts on biodiversity and that farmland under organic agriculture does not exhibit the dramatic declines of many plant and animal species as observed in areas dominated by conventional agriculture. In a recent survey of the literature, 76 published studies report that species abundance and/or richness, across a wide-range of taxa, was higher on organic farms than on locally representative conventional farms. These biodiversity benefits are derived form the specific environmental features and management practices employed within organic systems, which don’t rely on monocultures and associated agrochemicals but in turn encourage biodiversity and heterogeneity which provide critical habitat for wildlife.
The majority of organic farming systems tend to minimize energy and resource use, by recycling resources within the farming system and by enhancing biodiversity which in turn mediates ecological functions rush as pest regulation soil fertility and productivity. The basic components of sustainable organic systems are (1) use of cover crops, mulches, and no-till practices a effective soil an water-conserving measures; (2) promotion of soil biotic activity through the regular addition of organic matter such as manure and compost; (3) use of crop rotations, crop/livestock mixed systems, agro-forestry, and legume-based intercropping for nutrient recycling; and (4) encouragement of biological pest control agents through introduction and/or conservation of natural enemies via habitat management and crop diversification. Through the adoption of such practices, organic farmers aim to:
• buildup of soil organic matter and soil biota;
• minimization of pest, disease and weed damage;
• conservation of soil, water, and biodiversity resources;
• long-term agricultural productivity;
• optimal nutritional value and quality of produce;
• sequestration of carbon and thus mitigating climate change
• create an aesthetically pleasing environment.
Carefully designed, timed and intensively managed biodiverse cropping systems are vital in the integral management of soils, weeds, pests, and diseases. Plant diversity in annual and perennial crops can help restore soil fertility, increase biomass and reduce soil compaction and erosion. They also contribute to moisture retention, weed control, and enhance biological control of pests. The literature is full of examples of experiments documenting that diversification of cropping systems often leads to reduced herbivore populations because in such systems predators and parasitoids thrive thus regulating pest numbers below economic levels.
Organic matter rich soils contain a high biomass fungi, bacteria and actinomycetes, as well as animals such as nematodes, mites, collembola, diplopoda, earthworms and arthropods . A square meter of an organic temperate agricultural soil may contain 1,000 species of organisms. One gram of soil may contain over a thousand fungal hyphae and up to a million or more individual bacterial colonies. These organisms directly interact with plants through mutualisms and commensalisms, and in their role as regulators of soil ecosystem processes soil organisms perform a number of vital functions such as decomposing litter and cycling nutrients and converting atmospheric nitrogen into organic forms, as well as synthesizing enzymes, vitamins, hormones, and allelochemical that regulate plant growth.
Agroecology and biodiversity
Agroecology is the science that provides the guidelines to assemble biodiverse agroecosystems which rely for production of healthy food on ecological services such as the activation of soil biology, the recycling of nutrients, the enhancement of beneficial arthropods and antagonists, and so on. In agroecology, a main strategy is to enhance beneficial organisms through various combinations of crops, trees and animals in spatial and temporal arrangements such as polycultures, agroforestry systems and crop-livestock mixtures. Throughout the world agroecologists encourage these agricultural practices which increase the abundance and diversity of above and below-ground organisms, which in turn provide the ecological infrastructure that allows the production of healthy food without using external inputs thus de-coupling agriculture from strict petroleum dependence. Of key importance for planetary survival are observations of agricultural performance after extreme climatic events which reveal that resiliency to climate disasters is closely linked to high levels of farm biodiversity.
Rural social movements, agroecology and food sovereignty
The scaling up of a biodiverse and sustainable agriculture will require significant structural changes, in addition to technological innovation, farmer-to-farmer networks and farmer-to-consumer solidarity. A radical transformation of agriculture is needed, one guided by the notion that ecological change in agriculture cannot be promoted without comparable changes in the social, political, cultural and economic arenas that conform and determine agriculture. The organized peasant and indigenous based agrarian movements such as the international peasant movement Via Campesina and Brazil’s Landless Peasant Movement (MST) have long argued that farmers need land to produce food for their own communities and for their country and for this reason has advocated for genuine agrarian reforms to access and control land, water, and biodiversity which are of central importance for communities in order to meet growing food demands.
People's food security and health as well as the environment, food production has to remain in the hands of small-scale sustainable farmers and cannot be left under the control of large agribusiness companies or supermarket chains. Only by changing the export-led, free-trade based, industrial agriculture model of large farms can the downward spiral of poverty, low wages, rural-urban migration, hunger and environmental degradation be halted 28. Social rural movements embrace the concept of food sovereignty as an alternative to the neo-liberal approach that puts its faith in an inequitable international trade to solve the world’s food problem. Instead, it focuses on local autonomy, local markets, local production-consumption cycles, energy and technological sovereignty and farmer-to-farmer networks. Niche markets for the rich in the North exhibit the same problems of any agro-export scheme that does not prioritize food sovereignty, perpetuating dependence and hunger.
Social-rural movements understand that dismantling the industrial agri-food complex and restoring local food systems must be accompanied by the construction of agroecological alternatives that suit the needs of small-scale producers and the low-income non-farming population, and that oppose corporate control over production and consumption. Given the urgency of the problems affecting agriculture, coalitions that can rapidly foster sustainable agriculture among farmers, civil society organizations (including consumers), as well as relevant and committed research organizations are needed. Moving towards a more socially just, economically viable, and environmentally sound agriculture will be the result of the coordinated action of emerging social movements in the rural sector in alliance with civil society organizations that are committed to supporting the goals of these farmers movements. The expectation is that through constant political pressure from organized farmers and others, politicians will be more responsive to develop and launch a policies conducive to enhance food sovereignty, to preserve the natural resource base, and to ensure social equity and economic agricultural viability.
Consumers of the North can play a major role by supporting these more solidarious and equitable markets which do not perpetuate the colonial model of “agriculture of the poor for the rich”, but rather a model that catapults small biodiverse farms as the basis for strong rural economies in the South. Such economies will not only provide sustainable production of healthy, agroecologically produced, accessible food for all, but will allow indigenous peoples and small farmers to continue their millennial work of building and conserving the agricultural and natural biodiversity on which we all depend now and more so in the future.
Miguel A. Altieri,
University of California, Berkeley