African traditional leafy vegetables and the urban and peri-urban poor

Abstract

The importance of traditional leafy vegetables (TLVs) in nutrition and employment both in production and marketing among urban and peri-urban households was investigated. An expenditure model of demand using results from a 1998 survey (n=150) in Yaounde, Cameroon estimated that as a group TLVs were normal goods, which contribute a significant share of essential nutrients for the urban poor. Urban consumption of Brassica exotics, which have replaced TLVs in other parts of Africa, was minimal. Price analysis revealed a decline in supply during the dry season, which is a food security concern for the very poor. Field and market surveys conducted in 1998 and 1997 estimated that over 32000 households were engaged in producing and marketing TLVs under readily accessible entry conditions. Three production styles were identified: an intensive system within the urban limits, a semi intensive style in the urban periphery and an extensive style also in the urban periphery. The largest number of producers were women employing an extensive mixed crop system. Successful in situ conservation will require research to improve the productivity of TLV cropping systems and media efforts to promote their use.

Introduction

Leafy green vegetables are mainstays in the diets of rural and urban households across most of Africa. Among these, traditional leafy vegetables (TLVs), defined as having been originally domesticated or cultivated in Africa for the last several centuries, are in several areas being replaced by newly introduced species particularly from the Brassica genus including cabbage, kale, mustard green, and other species. This is noteworthy for several reasons.

There may be a negative consequence on nutrition particularly among the poor if exotic introductions with generally lower nutritional values are substituted for TLVs (Okafor, 1997, Udosen, 1995, FAO, 1988, Fube and Djonga, 1987, Chweya, 1985). There is also concern over a continued narrowing of the number of food species as fewer and fewer crops remain in local farming systems (Future Harvest, 2001). Associated with this loss is the disappearance of local knowledge for their production and use.

Unlike introduced vegetables that have been selected and improved by breeders for improved palatability, most TLVs have not benefited from such research. High levels of oxalic acid, nitrate, glycosides of hydrocyanic acid, and alkaloids in TLVs can cause urban consumers to seek substitutes. Oxalic acid has a negative influence on the bioavailability of calcium, magnesium and zinc and increases the risk of kidney stones (Wolters, 1992). In contrast, the Brassica genus is unique in the plant kingdom in that it does not accumulate oxalates. Thus even though total levels of calcium in these species is often lower, the actual amount available for absorption is often higher than for many TLVs.

The conservation of these crops is a concern of both national and international agricultural research centers in the region (Future Harvest, 2001). Strategies combining standard ex situ conservation with strengthened in situ efforts based on the promotion and improvement of these species for greater use are advocated (Eyzaguirre, 1997, Okigbo, 1994). Although the cultivation of traditional vegetables remains inculcated in the knowledge systems of many of Africa’s rural peoples, rapid urbanization especially in West Africa raise concerns over the disappearance of these economic and nutritional resources. On the other hand, many city residents are still first generation rural migrants who retain their preferences for these traditional foods and provide a base for efforts to promote the commercialization and use of these crops among both current and future generations.

The size of TLV markets in sub-Saharan Africa is substantial. In 1996 annual sales of TLVs in the urban markets of Cameroon were an estimated US$22 million, including the value of rural consumption, the estimated total market value was more than US$56 million. Production for urban markets is largely concentrated in the peri-urban zone due to the highly perishable nature of these goods combined with underdeveloped marketing and road infrastructure. In general, production and marketing activities are small in scale and dominated by resource-poor households. The size and structure of the subsector imply a significant contribution to the livelihoods of the poor living in the urban and peri-urban areas.

A strategy for improved TLV production and marketing requires addressing the agronomic, economic and cultural factors that constrain the expansion and competitiveness of these crops. As part of the strategy, the role of TLVs in the livelihoods of the urban and peri-urban poor should be explicitly recognized and addressed by the various poverty reduction strategies being developed in Africa. Towards that end the paper examines the multi-faceted ways in which TLVs affect urban and peri-urban livelihoods based on case studies of production, marketing and consumption around the urban center of Yaounde.