Environmental impact of organic agriculture in temperate regions

Summary

Can organic agriculture elaborate a scientifically based, resource-efficien and agroecological approach to low-input farm management? This review examines the literature from temperate regions, with a particular emphasison Canadian and USstudies that relate to environmental and ecological impacts of organic agriculture with respect to (i )soil organic matter storage, (ii) soil quality/soil health, (iii) nutrient loading and risks of off-farm nutrient and agrochemical losses, (iv) biodiversity and (v) energy use and global warming potential. The context and implications of semi-arid conditions and low soil P levels, common to many organic farms in North America, and wide spread adoption of genetically engineered crops in conventional production, is also considered. The consensus of the data available to date indicates the distinctiveness of cropping, flora and habitat diversity, soil management regime, nutrient intensity and use efficiency and energy, and pesticide use in organic farming confer important environmental and ecological benefits. These include maintenance of soil organic matter and added return of carbon to soil, improved soil health, reduced off-farm nitrogen and phosphorus losses, enhanced vegetative and wildlife (bird) biological diversity, extended some times to other taxa depending on landscape context, improved support for pollinators and pollination and reduced energy use and improved energy efficiency. The continued evolution of organic agriculture to a more outcomes-based, agroe cological production system will require an expanded multi-disciplinary research effort, linked ideally to support from consumers and policy-makers on the basis of renewed under-standing of its potential contribution to global environmental sustainability.