A literature review on wildlife habitats in agricultural landscapes
Agriculture, perhaps more than any other human activity, has an adverse, impact on wildlife. Clearing forested lands for agriculture, agriculture itself, and agriculture's side effects are the major causes of worldwide species loss. Farm effects are damaging because they are so widespread, about half the planet's land surface has been converted to agricultural use. In many regions of southern Ontario, home of Canada's best croplands, this figure may reach 90%. The central resource of farming is soil which itself harbours a large proportion of wildlife diversity and biomass, and about which we know so little. Responsibility for agriculture's environmental effects should not be shouldered by farmers alone. Modern farm practice responds to the priorities of an urbanized society which demands inexpensive farm products at the expense of the rural resource base. Farmers are under tremendous pressure to maximize production and profits through greater efficiency, and, in order to survive economically, they feel they must strip natural vegetation to expand and compete. Agriculture affects wildlife by reducing and isolating natural habitat. Often all that remains of natural habitat in heavily farmed areas are scattered remnant patches, wet depressions, and linear strips lost in a sea of cropland. An agroecosystem is a simplified, perturbed environment that replaces richer natural diversity with a relatively impoverished assemblage of cultivated plants and domesticated animals. Fewer native plants and animals adapt to, or can be tolerated in, intensively managed cropping systems. Recent trends in agricultural practices such as increased farm and field size, reduction of uncultivated field boundaries, increased chemical inputs, and lower crop diversity point to more ecosystem simplification, with ominous implications for local wildlife. This literature review critically examines the situation of wildlife habitats in agricultural landscapes with a particular view to finding ways that can enhance or restore the value of farmland for wildlife. The subject is a timely one, given Canada's stated support for sustainable use of wildlife and biodiversity. It is woefully inadequate to concentrate conservation efforts only on specially protected areas that cover only about 3% of the world land area, but ignore the vast remainder of the landscape managed for agriculture, forestry, and human settlement. What happens in this wider landscape, far more than conditions in protected landscapes, is now the single greatest limiting factor for the distribution and abundance of wildlife species. Two separate areas within agroecosystems will be examined, the crop fields themselves and the noncrop habitats with which they interface (field margins, fencerows, roadsides, ditches, woodlots). In each instance the approach will focus on the importance of habitat generally rather than on single-species habitat needs. By preserving appropriate habitat, we may be able to conserve most of our native species including the large array of smaller organisms such as invertebrates, fungi, and bacteria that receive little attention in most conservation efforts, but dominate both the biomass and diversity of organisms. Wildlife throughout this report includes plants, invertebrates, and vertebrates. The review ends with some suggestions for actions that should assist in enhancing or conserving wildlife within agroecosystems. There are some proposals for researching the managing of agroecosystems to establish whether some management techniques are more benign for wildlife than others. This all presupposes that the public at large can be convinced, and educated in the importance of managing wildlife resources within agroecosystems for common present common good, and benefit of future generations.