17 Managing Woodlands in Agricultural Environments
Clearing forest land for agriculture is a practice that has been ongoing for millennia. The process initially begins as a landowner enters a forest and clears enough land to meet the needs of a family. But when considering a landscape within which this occurs, the forest is still the matrix condition perforated by agriculture, at least initially. New settlers arrive, or the existing settlers realize that not only can they provide food for themselves but they can also sell excess food to others, so deforestation continues. Eventually, agricultural fields and pastures become the matrix condition with isolated patches of forest, or woodlots, remaining scattered throughout the landscape. If the landowner finds value in the remaining woodlots, then they are maintained, but if not, then they too are cleared and forest is lost until agricultural production is abandoned on that site. Much of New England is forest that was once agricultural fields or pastures, as evidenced by stone walls now criss-crossing a mature forest that has grown up over the past 70–150 years.
Much of the early research into the effects of forest fragmentation on a wide range of species was based on clearing forest land for agriculture until isolated woodlots remain within an agricultural matrix (Robbins et al. 1989, Villard et al. 1999). Hence, we know that many species associated with forests in the eastern United States are adversely affected by conversion to agriculture that leaves remaining woodlands in small patches that are disconnected from one another. The process continues to this day in the temperate and tropical regions of the world. Conversion to agriculture is a very broad sweeping term. What kind of agriculture—grazing, crops, livestock, etc.? Does it make a difference how the forest is converted and for what purpose? Belanger and Grenier (2002) reported changes in eastern Canada that have been documented in many other studies: As the area of land in agriculture increases, the number of woodlots increases but woodlot size decreases. They also reported that fragmentation increased along a gradient from dairy farms to intensive cash-crop agriculture. It would appear that the type of agriculture does influence the landscape structure and quite likely has effects on the species of animals and plants that can remain on the landscape. For some species, such as area-sensitive bird species (e.g., ovenbird), such changes in the configuration of the landscape can lead to regional declines in habitat and populations. For others, such as some bat species, fragmenting forests can lead to higher numbers of individuals (Ethier and Fahrig 2011). The purpose of this chapter is not to revisit the effects of forest fragmentation, but rather to ask what changes may be made to how we manage woodlots and the surrounding agricultural lands to alter habitat quality for selected species.
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