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Taking a closer look at agrobiodiversity

A variety of black maize has been traditionally grown and conserved by Mazahua upland hill farmers in Mexico. An unusual aspect of this variety is that it produces vivid blue tortillas, highly prized by local people not only for their colour but also their taste. More recently they have also become a popular niche product in urban areas. Yields are not high but the market price for this unusual commodity has aroused sufficient interest that black maize is now grown commercially by smallholders. Without the efforts and persistence of these campesino hill farmers, this black-grained maize would probably have disappeared.

Expert farmer harvesting yams, Ghana
credit: Prof. E. Gyasi, Univ. of Ghana

Smallholder farmers throughout the tropics are adept at using the natural diversity of the environment in which they live. This involves not only the crop species or varieties that they choose to grow but also the way in which they manage the soil, water, land and surrounding vegetation. Worldwide, many examples of land use systems and practices can be found which have withstood the challenges of population growth, economic pressure, and environmental change. However, much of this knowledge on 'agrodiversity' is largely untapped and often overlooked.

To take a closer look, a global project known as "People, Land Management and Environmental Change" (PLEC), supported by the Global Environment Facility (GEF), has established demonstration sites where 'agrodiversity' practice is especially valuable. At 30 sites worldwide (see box), many hundreds of farmers are collaborating with scientists, other professionals and policy-makers to show why on-farm biodiversity and its management are worth supporting and how it can be implemented. The approach of PLEC is to work with 'expert' farmers in devising ways of using natural resources that combine superior production along with enhancement of biological diversity at the farm and community level. Successful farmers go on to train other farmers and host policy forums to discuss better and more sustainable ways of protecting fragile natural environments. But the emphasis is on the dynamics of utilization and management rather than just conservation.

People, Land Management and Environmental Change
The PLEC project has cluster projects in East (Kenya, Tanzania and Uganda) and West Africa (Ghana and Guinea), the Pacific (Papua New Guinea) and in south-east Asia (China and Thailand) as well as in Central (Mexico and Jamaica) and South America (Brazil and Peru).

In the banana-based agricultural systems in Uganda, for instance, over 25 varieties of bananas may be grown on one homestead. Each variety may have a different purpose although some have multiple functions. The varieties on the edge of the banana grove are resistant to windthrow and serve to protect more vulnerable banana varieties which are used for roasting, beer brewing, for eating as sweet bananas as well as for fibres used in traditional crafts and toys. But the biodiversity in this system is not just about bananas; it involves the whole landscape. Ornamental species of grass provide a trap for water and sediment within the grove and on the upper slopes, leguminous crops are grown along with cassava and various cereal varieties.

In southeast Asia, in the Gaoligong Mountains, Chinese collaborators working with the project have documented 220 different agroforestry systems within one small area. These include fruit and spice trees mixed with ground plants and cereals. Each system is complex and takes some understanding. But as Michael Stocking, Scientific Co-ordinator of PLEC stresses, this is what the project is all about. "What our researchers are interested in is showing how these species mix together, how they are getting mutual benefit from each other, and how the land use needs and the requirements for food, shelter and security are being met by rural people. It is these mutual benefits, these win-win situations, where not only people's livelihoods are sustained, but also the environment is protected, that are of interest."

Back to basics

An interesting part of the research is not just to understand the overall use and sustainability of the local landscape but to look in more depth at the intricacies of why farmers use certain techniques; for example, for dividing the roots of yams; or for training certain yam varieties up particular natural forest trees in southern Ghana. Some answers are readily available; for instance, northern Ghanaian farmers can provide a number of explanations why African indigenous rice (Oryza glaberrima) is preferred to paddy rice: it has a short cooking time, it tastes good, it keeps well and it is good for weaning babies. However, why farmers decide to plant O. glaberrima varieties in one part of their holding but not another is not so easy to determine and requires scientific investigation to determine the rationale behind this management decision.

The objective of the PLEC project is not to spread technical fixes since what works well in one system may not be appropriate elsewhere, as each site is unique with farmers using different combinations of management techniques and crop varieties to support their livelihoods. However, an important element of the research is in raising awareness to policy makers. As Michael Stocking concludes, "I think many of us have been alarmed by the trend towards monocrops and heavy reliance on external inputs. So here then is a counterweight, which shows how very diverse agricultural systems can not only support people, but also protect the environment, and be sustainable in the long term future."

For further information: see PLEC project website at or DEV/ODG at or email

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