Wetland Functions and Values

In 1993, Harford Land Trust protected its’ first parcel, 103 acres of lake and stream bordered by marsh, shrub swamp and bottomland hardwood forest. The water from this wetland complex flows into the Bush River and ultimately into the Chesapeake Bay. Additional wetlands have been protected by the Trust since then, but why would a land trust work to protect “swamps”? Until the 1950’s, wetlands were generally regarded as wasteland, vile and treacherous places harboring dangerous people and haunted by evil spirits. Even words describing wetlands are homonyms with unpleasant meanings: bog, quagmire, swamp, muck and mire. Fortunately, scientific research over the past 60 years has clearly shown that wetlands and their ecological functions have great value to all of us.

Wetlands on the edge of lakes, rivers and bays, called riparian wetlands, reduce shoreline erosion. The wetland vegetation slows the movement of water, thus reducing its erosive power, and the roots and stems help hold the soil together.


All wetlands trap nutrients, carbon and sediments. As water enters wetlands, the vegetation reduces its’ velocity, causing the suspended sediments to settle out. During the growing season, the vegetation absorbs the nutrients phosphorus and nitrogen in the water and sediments, thus preventing them from entering bodies of water where they can promote excessive unpleasant and harmful growth of algae and bacteria. The vegetation also absorbs carbon dioxide, one of the gases causing global warming, from the air. When the vegetation dies, most of it gets trapped on the bottom along with the sediment and forms a water-saturated organic matter called muck or peat. Ecologists refer to this kind of situation as a “sink”, where components of an ecosystem become entrapped and are lost to ecosystem processes for a long time.


All wetlands reduce flood damage, but not all wetlands reduce the amount of flooding. Wetlands that do not occur on the edge of  water bodies absorb water in a sponge-like complex of soil, muck, partially decayed and dead vegetation which may hold up to 15 times its own weight in water. The water is then gradually released into the air and ground or surface water. This storage and gradual release reduces the frequency and severity of floods. Riparian wetlands, especially narrow ones, may not perform this function as effectively because they are saturated, but they do reduce flood damage simply because when they flood, nothing is damaged. The flooding of wetlands along rivers reduces flooding downstream on drier land.


Wetlands may or may not contribute to ground water recharge. When there is an impermeable layer of soil or rock below a wetland, the wetland is perched above the ground water and does not contribute to it. When a wetland is connected to ground water, water from the wetland recharges it and the water in the wetland may increase or decrease as the ground water rises or falls. Wetlands that gradually release water into ground or surface waters help maintain the flow of surface water, thus reducing the effect of drought.

Wetlands are wildlife habitat. The most representative and obvious species are waterfowl (ducks and geese), water birds (herons, egrets, and rails), semi-aquatic mammals (beaver, muskrat, mink and otter), and reptiles and amphibians such as frogs, newts and tiger salamanders, ribbon and water snakes, and painted, spotted, bog and snapping turtles. Some species of fish spawn in or adjacent to wetlands, where the young fish feed on the invertebrates and small fish. Yellow perch, for example, spawn on the debris in shallow streams that flow through wetlands and the young perch forage along the edge of marshes. Striped bass (rockfish) also forage along the edges of marshes in late fall, sometimes in large numbers. When blue crabs slough their hard shells, they seek the shelter of wetlands or the adjacent submerged aquatic vegetation until their new shells harden.


Wetlands provide recreation. I visit a Trust protected wetland near my home frequently and notice how other people enjoy it. In the late winter and early spring, bird watchers and photographers are attracted by the variety of ducks, especially the beautifully colored wood ducks and hooded mergansers. Later in the spring, experienced and well equipped bass anglers fish the open water. In the summer, young anglers with simple gear fish the shallows for three species of sunfish. Cardinal flower, crimson-eyed and rose mallow, pickerelweed produce an impressive display of red, white, rose and blue attracting people who enjoy wildflowers. Occasionally, canoeists and kayakers ply the still waters. The most frequent visitors, however, are people taking a short break from their daily routine to enjoy the natural beauty of the place and the unexpected pleasure of seeing a bald eagle catch a fish, a mink patrol the shore line, or dozens of painted turtles bask in the sun on a partially submerged log.

The Harford Land Trust is aware of how wetlands function in our ecosystem and how all of us benefit in one way or another from the values these functions produce. This awareness is why the Trust is committed to protecting wetlands, as well as forest and farm lands, for the people of Harford County and Maryland.