Many supporters of the grow-your-own-food-at-home movement claim that doing so can improve a city’s food security, with less reliance on external food sources needed to sustain its population. It sounds plausible, and the idea feels good but a US study showed that it just can’t be done. Even if you remove all your urban trees.
Researchers at Seattle’s Washington University School of Environmental and Forest Sciences used modelling to assess the output of Seattle’s urban farms against what is required to sustain its population. Inputs to the model included the mix of food crops necessary to maintain a year-round nutritious vegetarian diet, realistic land use scenarios where all possible land was devoted to crop growing (including home gardens, all public land, vacant lots and rooftops), soil types and availability of water and nutrients, suitable crop growing temperatures, and the effect of tree shading on land productivity.
While acknowledging that each city has its own unique MFCPC, Richardson and Moskal reported in the Elsevier journal of Urban Forestry and Urban Greening that, at Maximum Food Crop Production Capacity (MFCPC), only 1% – 4% of Seattle’s needs could be met by urban farming and that this reduces by around 20% if the existing tree canopy is retained.
The model found that to meet 100% of its food needs, Seattle would require a 58km radius food production belt.
So while you might enjoy growing food at home, and it may be more delicious and even nutritious, it’s not going to improve the food security of your city or town.
Journal: Urban Forestry & Urban Greening – Volume 15, 2016, Pages 58–64