Small-scale urban agriculture results in high yields but requires judicious management of inputs to achieve sustainability

Significance

Growing food in cities for human consumption could be one means of increasing global food supply in the face of rising population growth and global food security concerns. While previous studies have shown that urban agricultural systems are productive, few studies provide yield figures that incorporate data on the inputs used to achieve the outputs. Across 13 urban community gardens, we show that yields were nearly twice the yield of typical Australian commercial vegetable farms. However, economic and emergy (embodied energy) analyses indicated they were relatively inefficient in their use of material and labor resources. Balancing the sustainability of urban food production with the cost of inputs is important to determine the trade-offs required to achieve high yields.

Abstract

A major challenge of the 21st century is to produce more food for a growing population without increasing humanity’s agricultural footprint. Urban food production may help to solve this challenge; however, little research has examined the productivity of urban farming systems. We investigated inputs and produce yields over a 1-y period in 13 small-scale organic farms and gardens in Sydney, Australia. We found mean yields to be 5.94 kg⋅m ⁻², around twice the yield of typical Australian commercial vegetable farms. While these systems used land efficiently, economic and emergy (embodied energy) analyses showed they were relatively inefficient in their use of material and labor resources. Benefit-to-cost ratios demonstrated that, on average, the gardens ran at a financial loss and emergy transformity was one to three orders of magnitude greater than many conventional rural farms. Only 14.66% of all inputs were considered “renewable,” resulting in a moderate mean environmental loading ratio (ELR) of 5.82, a value within the range of many conventional farming systems. However, when all nonrenewable inputs capable of being substituted with local renewable inputs were replaced in a hypothetical scenario, the ELR improved markedly to 1.32. These results show that urban agriculture can be highly productive; however, this productivity comes with many trade-offs, and care must be taken to ensure its sustainability.