All land, including agricultural land, provides habitat for wildlife (flora and fauna), but its composition and quality is highly variable. Agricultural activities can impact on wildlife and their habitats directly by the conversion of uncultivated natural habitats to crops or forage, and indirectly through disturbances of these habitats, such as the effects of elevated pollutant discharges.
OECD countries are paying greater attention to improving the quality of habitat on farmland because of the growing value society is placing on such habitats as sites of environmental and recreational value. Policy actions have focused on protecting endangered agricultural habitats and encouraging farmers to adopt management practices beneficial to habitat improvement. Some policy initiatives are being established to meet international commitments, such as the Convention on Biological Diversity.
Six indicators are being developed by OECD related to agriculture and wildlife habitat. Five indicators monitor the state and trends in intensively farmed, semi-natural, and uncultivated natural habitats. The importance of these habitats for wildlife differ widely. Intensively farmed land can be important for biodiversity where hedges, etc., are maintained, while semi-natural habitats are often rich in biodiversity. A sixth indicator is a habitat matrix, which identifies and relates the ways in which wild species use different agricultural habitat types.
For most countries since the mid-1980s the decline in the intensively farmed land area (arable and permanent crops), has been more rapid than for extensively farmed land (pasture), with production on the remaining intensively farmed land increasing through improving productivity. These developments have in many cases led to the conversion of habitat to cropped land and increased pollution levels threatening and endangering wildlife species. Since the late 1980s, however, the introduction of agri-environmental and land diversion schemes has helped improve certain highly valued agricultural habitats, led to the recovery of some wildlife species, and reduced diffuse pollution. But it is too early to know the extent and permanence of these changes.
Changes in the area of semi-natural habitats on agricultural land show considerable variation, for the few OECD countries where data are available. For certain countries these habitats cover more than 50 per cent of the total agricultural land area and have increased since the mid-1980s, partly because land diversion schemes have led to the shift from arable land to fallow and pasture. Semi-natural agricultural habitats that have been converted to other land uses, especially to forestry, is often because of their location in marginal farming areas.
Concerning uncultivated natural habitats, in the case of the conversion of aquatic ecosystems and natural forests for agricultural use, there is little comprehensive data across OECD countries. For the countries where data are available, over the past decade more aquatic ecosystems have been restored than converted to agriculture, although for a few countries there has been a net conversion of aquatic ecosystems to farm land. The conversion of agricultural land to woodland and forest represents a significant share of total agricultural land conversion over the past decade, but it is not clear whether these changes represent the conversion to natural or semi-natural wooded areas or commercial forest.
Some countries are starting to establish a habitat matrix to examine the impact of agricultural land use changes on wildlife, with initial results showing that all agricultural land offers a variety of habitats for wildlife, but some types are superior to others. Also changes in land use from less to more intensive practices, such as bringing marginal land into crop production, create pressures on wildlife by, for example, reducing the availability of breeding areas.