MANY cities of developed and developing countries have some form of farming activities in and around the urban periphery that include the cultivation of food and cash crops including flowers, garden plants, forestry and animal husbandry.
In Pakistan, 50,000 hectares are used for growing vegetables and fodder due to easy access to nearby markets. Crops grown around cities are affected by urban pollution caused by input of solid wastes, municipal effluent and atmospheric pollution.
At present, major urban areas generate more than 60,000 tons of solid waste and 1800 million gallons of raw municipal effluent daily. Due to the shortage of collection equipment, manpower, financial resources and lack of management in urban areas only 50 per cent of the solid waste generated is collected, whereas the remaining waste is disposed of in open dumps, arable lands and water bodies. These waste disposal sites lack technical and environmental controls and operate without adequate equipment or sufficient cover material.
Sewage, treated or not treated, is usually discharged into drains, rivers and coastal waters downstream from population centres, and its inherent fertility is lost. On the other hand, with growing water scarcity for agriculture and increasing wastewater volume farmers around cities find it convenient to irrigate the fields with easily accessible municipal effluent. Use of raw sewage effluents along with other city waste in agriculture makes the urban agriculture unhealthy enterprise.
Multiple problems can occur when solid wastes are applied or raw sewage is used for irrigation. Sources pollution are air, soil, water, excreta and other solid and liquid wastes that may reach producers, handlers, and consumers via other plant and/or animal vectors or carriers.
Heavy-metal and pathogenic contamination are a particular concern. Uptake of heavy metals by vegetables and particularly leafy vegetables is more than cereals. Furthermore, heavy metals in soil and air, particularly lead in urban environment are major contaminant that green leafy vegetables can concentrate in their leaves.
Parasitic diseases and veterinary public health issues can arise from livestock production methods without proper space and sanitation and appropriate management and monitoring of resources with negative environmental and health effects.
There are certain environment benefits associated with urban and peri-urban agriculture including utilisation of resources like the municipal wastes, recycling of plant nutrients, greening of urban environment thus decreasing net discharge of carbon dioxide to the atmosphere and ultimately creating healthy environment.
Risks associated with the use of waste can be minimised through the use of composted organic urban wastes, treated municipal effluents, selection of right crop, changing planting technique and controlled irrigation.
Cities are considered in terms of housing, transport, commercial services and industry, rather than in terms of agriculture, which generates relatively low yields. Agriculture in urban areas interferes with more productive use or rent of land by other economic activities. Other constraints include inadequate institutional/legal frameworks; inadequate technical knowledge of urban agricultural practices; poor rating of urban agriculture as an authentic urban land use.
Within urban areas, urban agriculture is a weak competitor against other development uses. Land for potential food production in around cities is shrinking rapidly and what is available is being polluted with dumping of contaminated wastes.
Limited qualitative and case study data exist and contribute to understanding urban agriculture; a more comprehensive set of basic data is needed. The priority needs include numbers, location and characteristics of farms, volume and type of food produced, costs and prices of food produced and sold, both in formal and informal markets, income earned from farming, inputs used and methods used in urban and peri-urban farming, environmental impact analysis, veterinary public health effects of use of urban wastewater and solid waste, water needs and availability among all competing uses.
As a principal issue, it is proposed that urban farmers and consumers should receive more information and training on environmental risks (e.g. sewage irrigation and composting techniques) because more cities are required to try to use agriculture to curb pollution from wastes and optimise usage.
A fundamental step in order to set the right conditions for city farming is to develop an urban agriculture plan and policy, recognising the interrelated nature of food, agriculture, health and ecology by forming a municipal working group that can deal with food issues from a total system perspective.
If the potential of urban agriculture is going to be realised, much more has to be done than what is happening in many cities at present. What is needed is a policy for the city that focuses on encouraging the productivity of open urban space, integrating the various components necessary to make urban agriculture healthy and sustainable, and combating bad practices where necessary.
Prospects for urban farming are good. However, it is crucial that planners start recognising the importance of urban farming in the rich mix of activities that characterise modern cities. As the world urbanises, greater local food self-reliance, using nutrients accumulating in our cities, must be regarded as an important aspect of sustainable urban development.
The role of urban agriculture with regard to water and organic material flows has to be investigated. Research is also needed to quantify the impact of reusing excreta, wastewater and organic solid waste on food quality and the environment.
Together with initiatives on energy efficiency and high resource productivity and urban/peri-urban agriculture has an important contribution to make towards shaping the cities of the future.