What are Coastal Marshes?

Coastal Marshes are a crucial ecosystem which influence, and are influenced by, many natural forces and human industries. Coastal marshes are wetlands with fresh water, brackish water or salt water along tidal shores. A transect of a 'typical' coastal marsh could include seawater, short salt marsh grasses, taller salt marsh grasses and other plants, brackish water plants on slight elevation, and, finally, taller brackish water plants on land above high tide. The biome includes plants which thrive on salty or brackish water, and the many animals which inhabit this rich environment.

In much of the eastern United States, the dominant plant species for coastal salt marshes is Spartina alterniflora. This grass (also called "cordgrass") grows from 2-6 feet tall and inhabits the salt marsh landscape from sea level to 1-4 feet above sea level. The interconnected root system of these grasses anchors the soil in the face of tidal activity. If the spartina population is healthy, and conditions are right, the marsh may grow to fill in tidal ponds and creeks. If the spartina population is not healthy then tidal ponds and creeks may expand, reducing the land surface to water. Spartina grasslands form much of the quickly identifiable salt marshes along of the US east coast. The plants provide food and shelter to many mammals, birds, fish and invertebrates, resulting in one of the most critical plant communities on the continent.

Unfortunately, coastal marshes have been in decline all along the east coast of the United States. Historic reasons for decline include a common perception of any marsh as an undesirable landform, as a place where disease and evil airs were born. Marshes were also drained all along the east coast in an effort to eradicate mosquitos. Marshes have been used as dumps, they have often been overhunted, and have been subject to numerous other abuses. Since many coastal marshes coincide with areas of great human population concentrations along the eastern seaboard they have often been filled to increase habitable land. Coastal marshes are also very proximate to most east coast tourist beaches, stretching from Maine to Florida. As a result, they have been filled or otherwise constricted as development expanded tourist communities. Other human-induced factors, such as air and water pollution, global warming, and rising sea levels have also afflicted coastal marshes. Effects of direct and indirect human encroachments have resulted in the obliteration of many marshes, and the declining health of many others. Coastal marshes today are one of the most endangered ecosystems in North America.

Coastal marshes are crucial as incubators for fish and invertebrates, and play a vital role as habitat for migratory waterfowl. Human industries such as seafood and tourism are dependent upon healthy coastal marshes both for their ability to produce and sustain life and for their ability to transform human pollution to less toxic materials. Most people barely notice coastal marshes, but are influcenced by their role in our overall environment, and in providing a healthy coastal environment in particular. They are a critical factor in the complex web of life for both the oceans and land ecosystems. It is imperative that remaining coastal marshes be protected, and their health enhanced wherever possible. This is important for the environment, and for all people who share this planet.

Work sponsored by

NASA's   Mission to Planet Earth (Earth Science Enterprise, since 1998)
and the Department of Geography at the University of Maryland, College Park.