Effect Of Local Food Production On Phosphorus Budgets and Flows In Metro Vancouver and Peri-Urban Lower Fraser Valley.

Recent studies have examined phosphorus (P) budgets separately in urban and agricultural regions but there have been few studies that have quantified the impact of local food production in peri-urban regions on regional P budgets. This is a subject of growing concern as people increasingly try to source local food. This study explored the relationship between local food production and the P balance in a the lower Fraser Valley, BC, Canada, a compact region with  intensive dairy, poultry and horticultural production and a growing human population of 2.5 million which includes Metro Vancouver. Most P enters the region as agricultural feed and fertilizer. Most of the food produced in the region is consumed locally, but only 8% of the P imported for food production is consumed as local food, the remainder is in various waste products or left in soils. Other important regional P inputs include non-local food, feed for pets and horses, fertilizers for gardens and amenity areas, and soaps. The quantity of P exported by urban waste water treatment plants (mostly into waterways) is similar to the quantity of P imported as food and soap. Solid waste from humans, pets and horses is mostly sequestered in landfills. Only 4% of imported P is known to leave the region for agricultural uses but does not return to regions that produce the imported feedstuffs. There are currently few data on exported food processing waste and poultry litter. Technologies and policies are needed to improve the regional P balance through importing less feed, fertilizers and food, recycling more P locally, and exporting more waste back to feed producing areas.