Habitat FragmentationEssential Knowledge for Naturalists
Fragmentation occurs in conjunction with habitat loss, and leads to edge effects, with concurrent loss of critical interior habitats. because certain species need interior habtitats to survive, and because edges and isolated patches do not provide the factors needed for certain species to survive, fragmentation leads directly to a loss of biological diversity.
As wild land is cleared for farming, or more likely in Ohio these days, for residential subdivision, plant and animal habitat is lost. You might thing a few hundred acres here or there couldn't possibly make much difference, but it does. Not only do certain animals need a minimum range size, but animals also need to be able to move between ranges, such as when young animals grow and begin to establish their own home ranges. Habitat loss, turning a chunk of natural land into one hundred lawns, takes land away from the wildlife and plants of a region.
We are often left with isolated patches of a certain habitat. 20 acres of forest here, a 10-acre protected wetland there. How are plants and animals to migrate or travel from isolated patch to isolated patch? What happens when small populations are separated from the larger populations of which they were a part? Could the loss of the population in one isolated patch degrade the future genetics of the whole species? Yes. Could it be inconsequential? Yes. Should we take the chance?
Not only does habitat loss lead to isolation. It leads to increased edge effects.
Edge EffectsEdge effects are, very simple, the effects of edges on habitat conditions. Edge effects are well-documented. These effects can be observed at least 30 meters (about a hundred feet), and in some cases, 300 meters (nearly 1000 feet) into a forest from a field edge. Temperature is higher in edges, humidity changes, soil moisture is decreased, and there is more wind in an edge. Increased sunlight causes a different mix of species to grow in edges.
Edge effects impact not only the forests, but animal species as well. For instance, brown-headed cowbird predation is much greater in edges than in interior forests. These birds break the eggs of other bird species, and then replace the broken eggs with their own. The victims of these parasitic birds then raise the offspring of the cowbird, feeding and caring for them as if they were their own.
With edge effects extending so far into a patch, and with habitat loss creatign smaller and smaller patches of habitat all the time, it is a wonder all of our forests are not just edges consisting of light-loving trees. Luckily, we still ahve interior forests. The next time you hike a trail look for edges and see if you can tell where the edge effects disappear.