Monday, March 10, 2008

What makes a Swamp a Swamp?

What makes a Swamp a Swamp?

When evaluating real estate, I often hear people say, "oh, no, there's never any standing water, so it can't be a wetland". However, many types of inland wetlands are never actually flooded with surface water. Our last article dealt with streams and floodplains, but in other protected areas the wetlands are, for the most part, underground.

Most common in our neck of the woods are the wooded swamps that act as sponges holding moisture, releasing it gradually into the abutting streams and rivers. These areas, protected in Massachusetts as "BVW's" or "Bordering Vegetated Wetlands" are dominated by trees, such as red maples, yellow birch, elm and ash. The shrub layer may include blueberry, spicebush or silky dogwood, and the ground is likely to be covered with cinnamon, sensitive and royal ferns, skunk cabbage, jewelweed, and spagnum moss. Wildlife make use of the trees, even the dead and dying ones, for nesting, feeding, roosting or perching. At their feet, the hummocky ground creates depressions that seasonally fill with water, referred to as vernal pools, where salamanders and frogs congregate and lay their eggs.

Many birds and mammals also inhabit wooded swamps: warblers and wood thrushes depend on large tracts of unbroken woodland for habitat, and snags serve as dens for raccoons, skunks, possums and fishers. Wood ducks, and owls nest in the larger cavities as well. Small mammals can tunnel and burrow in the soft, moist hydric soils of forested wetlands, and include voles, shrews, mice and moles.

Vernal pools are extremely important breeding habitats. Wood frogs, and mole salamanders breed exclusively in vernal pools, where there are no fish to devour their egg masses, and a vernal pool's loss can eliminate an entire breeding population. Turtles, herons and snakes rely on the abundant prey in vernal pools, including fairy shrimp and other mollusks, insects and crustaceans. Such pools form from snow melt, and disappear by early summer.

Forest fragmentation lessens the overall habitat value of an area by breaking up large contiguous tracts of woodland into smaller and smaller pieces, thereby cutting off access for animals with larger home ranges. It also creates easier access to nests and young for predators, and has caused the decline of many forest interior birds that nest exclusively in large, undisturbed tracts of woodland.

If you're lucky enough to own or abut a wooded wetland, you've enjoyed the quacking woodfrogs, the chirping spring peepers, and the magical trill of the woodthrush. Protecting their habitat is one more important interest under Massachusetts environmental regulations.

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