Organic farming practices have been promoted as, inter alia, reducing theenvironmental impacts of agriculture. This meta-analysis systematically analysespublished studies that compare environmental impacts of organic and conventionalfarming in Europe. The results show that organic farming practices generally havepositive impacts on the environment per unit of area, but not necessarily per product


2unit. Organic farms tend to have higher soil organic matter content and lower nutrientlosses (nitrogen leaching, nitrous oxide emissions and ammonia emissions) per unit of field area. However, ammonia emissions, nitrogen leaching and nitrous oxideemissions per product unit were higher from organic systems. Organic systems hadlower energy requirements, but higher land use, eutrophication potential andacidification potential per product unit. The variation within the results acrossdifferent studies was wide due to differences in the systems compared and researchmethods used. The only impacts that were found to differ significantly between thesystems were soil organic matter content, nitrogen leaching, nitrous oxide emissionsper unit of field area, energy use and land use. Most of the studies that comparedbiodiversity in organic and conventional farming demonstrated lower environmentalimpacts from organic farming. The key challenges in conventional farming are toimprove soil quality (by versatile crop rotations and additions of organic material),recycle nutrients and enhance and protect biodiversity. In organic farming, the mainchallenges are to improve the nutrient management and increase yields. In order toreduce the environmental impacts of farming in Europe, research efforts and policiesshould be targeted to developing farming systems that produce high yields with lownegative environmental impacts drawing on techniques from both organic andconventional systems