Horticulture in urban eco-systems: some socio-economic and environmental lessons from studies in three developing regions
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In the light of the documented prevalence of peri-urban horticulture in developing countries, the paper highlights the need to identify and resolve health risks associated with the urban location of these systems. Contamination of vegetables with heavy metals from vehicle emissions in Kampala occurred at different levels depending on location and affected storage roots, stems and leaves in different ways. Horticultural species thus need to be selected according to location and the plant part consumed. Preliminary results from Kampala also show penetration of plant tissue by pathogens, indicating that under pathogen risk, producers should plant species for cooking. To understand pesticide risk, pest management aspects of different urban farming systems were characterized. In intensive peri-urban systems, pest management is strongly related to market pressure rather than the ecology of plants and farm, with widespread preventive spraying, extensive use of highly toxic pesticides in several sites, and late spraying common. Evidence of residues was found right along the value chain of jasmine flowers, up to distribution of garlands. Because urban agriculture often involves agricultural migrants and non-farmers, indigenous knowledge may be less robust than in rural agriculture. Knowledge of pest biology or dynamics for example was found to be limited. Hanoi findings indicate a correlation between time spent in urban agriculture and reduced pesticide use. Sources of pest management knowledge are limited, mainly based on local vendors of pesticides. Although the market exercises a powerful influence on these systems, producers also seek new crop management learning opportunities. Urban-adapted Farmer Field Schools for integrated crop management have been introduced in Lima and Philippines. The involvement of local government authorities in this learning process has been important and needs to be an integral part of a sustainable strategy for urban horticulture systems.