Agriculture has a major impact on the environment in OECD countries. It accounts for around 40% of total OECD land use and nearly 45% of water use, and, in many countries, dominates and shapes the landscape.15 Agricultural activities have both beneficial and harmful effects on the environment through changing the quality or quantity of soil, water, air, natural habitats, biodiversity and landscapes. The relative importance of different environmental issues depends on the effects of farming practices at the local, regional, national and international levels, which in turn reflects variations in ecological and climatic factors. The scope and priority accorded to different environmental issues can also vary across countries and regions, depending on such factors as population density, income levels and the value attached to cultural heritage.