– by Bet Zimmerman and Paul Wilbur
Forest fragmentation poses a serious and growing threat to the ability of forests to support wildlife, clean air and water, provide recreational opportunities, and function as a sustainable and economically viable source of wood products. From 1994 to 1997, new single-family homes consumed an average of 2.16 million acres per year of land not previously used for housing. By 2010, some 150 million acres of productive private forestland will be owned in parcels of 100 acres or less, and the average holding will be about 17 acres (Sampson 2000).
Forest fragmentation occurs when large, contiguous blocks of forest are broken up into isolated islands by development, roads, or clearing for agriculture. The resulting geographic isolation leads to inbreeding and diminished biodiversity. Just as inbreeding among the royal families of Europe spread hemophilia, forest fragmentation negatively impacts the long term sustainability of both plant and animal communities. Migratory pathways for birds are lost. Scientists also suspect that fragmentation harms many woodland birds by making them more susceptible to predation by jays, crows, raccoons, and cats – creatures not typically abundant in extensive forests. The encroachment of roads into forests greatly increases the odds that animals that are migrating, seeking food, partners or breeding habitat will end up as flattened fauna. Negative interaction with homeowners can also occur, as hungry deer feast on landscape plants, and coyotes, fox and fishers chow on household pets.
Forest fragmentation can also decrease water and air quality, as the impervious surfaces of roads, parking lots, homes and businesses replace woodland plants, trees, and soils that previously stored carbon dioxide, produced oxygen, absorbed pollutants and protected against erosion. Increased run off and the introduction of nonpoint source pollutants diminish the function and change the character of the forest wetlands.
Breaking forests into small parcels can even impact human health. While fragments generally have fewer species than continuous habitat, some species like white-footed mice actually do better in small patches, probably because there are fewer predators and competitors left. White-footed mice populations are high in fragments smaller than about five acres, which could mean trouble for people living nearby, since the mice are the main carriers of Lyme disease bacteria. In one study, fragments smaller than three acres had an average of three times as many total deer tick nymphs as larger fragments did, and seven times as many infected nymphs. As many as 80% of the nymphs were infected in the smallest patches, the highest rate the researchers have seen.
Finally, forest fragmentation has an economic impact. When forests are broken into small parcels, the economy of scale for forest management is lost. It is just not as cost efficient to employ a forester, move people and equipment, arrange for trucking, and manage the sale of ten acres of forest as it is for larger tracts. As population increases in the countryside, farming and forestry decrease and the infrastructure that supported it moves away. This makes it less economical to maintain farms and large tracts of forest. The parcels are then broken up even more, in a downward spiral. The loss of farm and forest lands to development also adversely affects the tax base of our towns. Homes cost more in services then the taxes they bring in, while open spaces bring in more taxes than the cost of the services they use, mainly because cows and trees don’t need to be educated.
Large unfragmented forests = healthy forests and wildlife, healthy water and air, healthy humans, and a healthy pocket book.