Agricultural Ecosystems
- Men and women rice farmers working in Nepal. Credit: B. Sthapit/Bioversity
Managing genetic resources on farms concerns the entire ecosystem, including cultivated crops, forages and agroforestry species, as well as their wild and weedy relatives that may be growing in nearby areas.
There are many benefits from effective on farm genetic resources management programmes.
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Conserving the processes of evolution and adaptation
The conservation and use of agrobiodiversity at all levels within local environments helps ensure that the ongoing processes of evolution and adaptation of crops to their environments are maintained within farming systems. This benefit is central to in situ management of genetic resources, as it is based on conserving and using not only existing germplasm but also the conditions that allow for the development of new germplasm.
Conserving and using diversity at different levels
In its maintenance of farming systems, on-farm conservation applies the principle of conservation and use to all three levels of biodiversity: ecosystem, species and genetic (intraspecific) diversity. In conserving the structure of the agroecosystem, with its different niches and the interactions among them, the evolutionary processes and environmental pressures that affect genetic diversity are maintained and this contributes to the overall health of the local environment.
Integrating farmers into a national plant genetic resources system
Farmers are likely to know the nature and extent of local crop resources better than anyone through their daily interactions with the diversity in their fields. Given their expertise, incorporation of farmers into the national genetic resources system can help create productive partnerships for all involved. This integration can happen in several ways, including:
- Seeing farmers as partners in the maintenance of selected germplasm
- Establishing a national dialogue on biodiversity conservation, sustainable use and equitable benefit-sharing between farmers, genebanks and other partners
- Assisting the exchange of information with and among farmers from different sites and projects
- Farmers visiting genebanks or seeing demonstrations by genebanks
- Developing systems to make genebank material more easily accessible to farmers.
Improving the livelihoods of resource-poor farmers
In situ on farm genetic resource management programmes also have significant potential to improve the livelihoods of farmers at the local level. On-farm conservation and use programmes can be combined with local infrastructure development or the increased access for farmers to useful germplasm held in national genebanks.
Farmers benefit from the continued agricultural diversity and ecosystem health that these programmes support. Local crop resources can be the basis for initiatives to increase crop production or secure new marketing opportunities. By building development efforts on local resources and through the empowerment of farming communities, they can lead to sustainable livelihood improvement. Resource-poor farmers, in particular, may benefit if development initiatives are not based on external inputs that may be costly or inappropriate for marginal agroecosystems.
Maintaining or increasing farmers control and access over genetic resources
On-farm conservation and use also serves to empower farmers to control the genetic resources in their fields. On-farm genetic resource management recognizes farmers and communities as the curators of local biodiversity and the traditional knowledge to which it is linked. In turn, farmers are more likely to reap any benefits that arise from the genetic material they are managing.
Managing stress and change
Managing agroecosytems and the biodiversity they contain is essential for human health and nutrition and for the continued availability of food and other agricultural products.
Crop diversity can be used as a resource to mediate potential stresses of the surrounding environment. A crop population with a diverse genetic makeup may have a lower risk of being entirely lost to any particular stress, such as temperature extremes, droughts, floods, pests, and other environmental variables. Crops with different planting times and times to maturity give the farmer the option to plant and harvest crops at multiple points in the season to guard against total crop loss to environmental threats.
Farmers shape the degree and distribution of genetic diversity in their crops both directly, through selection, and indirectly, through management of different agroecosystem components. For many farmers in developing countries, the availability of adaptive varieties for particular micro-niches may be one of the few resources available to increase or maintain production on his or her field.
Seed systems and diversity maintenance
Each year farmers decide how much seed to plant and where that seed comes from. These seeds may come through formal and informal systems, and may contain new combinations of genes that result from hybridization and introgression between wild and cultivated plants or among cultivated varieties.
Whether new combinations of genes or new seed types are maintained, with the resultant development of populations with new characteristics depends on farmer management and access. Rather than being passive recipients of seed from the formal sector (government, extension agencies, seed companies), farmers participate in dynamic networks of seed exchange and development.
On farm biodiversity management programmes that support strong seed supply systems can foster increased use of diversity while fulfilling certain types of farmer seed demand. Strong seed supply systems enable farmers to maintain a high level of diversity over time, despite losses of seed stock, bottlenecks, and other regular or unanticipated losses of crops genetic diversity.
Research on seed systems has shown that:
- a very large percentage of the seeds used by farmers in developing countries is acquired by informal means such as local markets, friends and relatives
- farmers engage in the innovation of new varieties by actively seeking our new seed or saving seed of plants that display new traits in their fields
- farmers retain diversity according to environmental conditions, market demands, culinary and aesthetic preferences, and social factors like religion and prestige
- farmers blend modern and traditional varieties.
Seed systems may shape crop genetic diversity and that seed systems can act as linkages between very distinct populations.
Ecosystem services
One commonly cited justification for maintaining plant genetic diversity in agricultural production systems generally, and in farmers' fields in particular, is its ability to buffer or limit disease and pest epidemics. When many farmers sow varieties that carry the same genetic mechanism of resistance to a plant disease, the crop is vulnerable to epidemics. The complexity of crop-pest interactions in agroecosystems is compounded by their seasonal or annual variability, particularly in stressful environments of extreme temperatures and unpredictable rainfall.
Combating epidemics once they occur can be costly to society both in terms of garnering the resources necessary to control them and the yield losses incurred, and especially so in developing countries.
By conserving and harnessing ecosystem biodiversity, on farm genetic resource management programmes can provide other valuable services to farmers. For example, the value of having a diversity of pollinators, such as bees, butterflies, hummingbirds and even bats is immense. Plus, soil biodiversity helps keep farmers' field fertile.
Linking wild and cultivated systems
On farm biodiversity management programmes can serve to increase out knowledge about the links between wild crop species and cultivate ones.
Whether new combinations of genes that result from hybridization and introgression between wild and cultivated crops are maintained, with the resultant development of populations with new characteristics, depends on natural selection, and in the case of crops, on human selection.
While many cases of deliberate introgression of desirable traits into crop cultivars as part of breeding programs are known, the extent and significance of natural or farmer assisted introgression is uncertain. A range techniques has been used to document natural hybridization and introgression of agricultural crops and their wild relatives in many crops including maize, wheat, barley, oats, pearl millet, foxtail millet, quinoa, hops, hemp, potato, casava, common bean, cowpea, pigeon pea, carrots, squash,tomato, radish, lettuce, chili, beets, sunflower, cabbage, and raspberries. However, the majority of these studies are based on morphological characters, and few have investigated the frequency with which such new types are produced and retained in natural and agroecosystems for farmer selection.
Even more limited is information on the role of farmers in recognizing and selecting new genetic variation from the natural introgression of crops with their wild relatives, and the impact, once selected, of these new genetic combinations on the crop diversity.
