THE URBAN AGRICULTURE REVOLUTION

摘要

Urban agriculture accounts for almost one-fifth of global food production, contributing to food security and livelihoods for many people in the developing world. Non-commercial urban food production - in household backyards, schools and community gardens - is also a fast-growing activity in developed countries due to rising food costs and greater awareness of the health and social benefits from fresh, local and largely organically produced fruits and vegetables. Meanwhile, commercial food production in the peri-urban fringe remains under threat from urban encroachment due to ongoing greenfield property development. There is a paucity of data regarding resource inputs - in particular irrigation water - required to support urban agriculture. As such, it is unknown whether the scaling up of urban food production would result in an impractically large increase in mains water consumption. On the other hand, this may create a much-needed demand for surplus irrigation-quality treated stormwater and wastewater that is currently discharged to the sea in many cities. This paper addresses the large knowledge gap relating to water consumption in urban food production. We first explore the theoretical extra water use (per capita) demanded by a realistic selection of fruit and vegetable crops grown in Adelaide, Melbourne, Hobart and Perth. We then extend this to a hypothetical practical irrigation rate that is - plausibly - less efficient than the theoretical crop water use, but more consistent with irrigation practice in urban gardens. We conclude that although urban water use would increase substantially, in principle the surplus volume of recycled wastewater and stormwater should be sufficient to offset the growth in water demand from urban food crops. Moreover, we find that certain crops may simply be uneconomic in an urban setting, due to the high costs of either mains or recycled water.