Geological Survey Circular 1085 Our Changing Landscape: Indiana Dunes National Lakeshore

(Gary North)

America's wetlands are decreasing in area every year. During colonial times, about 200 years ago, the contiguous United States had an estimated 221 million acres of wetlands—an area roughly the size of Texas and Oklahoma combined. Today approximately 100 million acres of wetlands remain—an area about the size of Montana. It is estimated that over the 20 years between the mid-1950's and the mid-1970's, net wetland losses from natural processes and human activities averaged 450,000 acres annually. There are many reasons for this loss, including urban and agricultural development and coastal erosion. Recognizing the vital importance of wetlands to the commercial and recreational sectors of our economy, as well as to the biological diversity of our Nation, many agencies currently are making efforts to protect, maintain, and restore wetlands.

Wetland distribution around the 1780's (top) versus wetland distribution around the 1980's (bottom). (Modified from Dahl, 1990.)

Wetlands can be found near coastal areas or in the middle of the Nation, miles from any coast. They comprise about 4 percent of our Nation's land area within the contiguous United States. Alaska has the largest proportion of wetlands area of all the States, much of it in tundra regions. Because wetlands are found in both coastal and inland areas, the water can be salty, brackish, or fresh. Wetlands occur along rivers, ponds, bays, and inlets—wherever the ground water is at or near the land surface, or where the land is covered by shallow water during part of the year.

Wetlands have many beneficial purposes, such as helping store and purify water and acting as natural filters. The U.S. Bureau of Mines has created artificial wetlands to treat acid-mine drainage; more than 300 wetlands have been constructed and successfully used to date. Wetlands also are habitat for fish and wildlife. In fact, coastal salt-marsh wetlands produce more plant and animal life than any other natural habitat known. Freshwater wetlands rank third in number of total plant and animal species behind saltwater marshes and tropical rain forests. Eighty percent of the Nation's coastal commercial and recreational fisheries depend upon wetlands for spawning, hatchery, and nursery activities. Some wetlands can store large volumes of water and can thereby serve as natural water reservoirs and as ground-water discharge areas. The presence of wetlands in a flood plain can reduce the size of floods by as much as 80 percent.

Wetlands are important nesting sites for birds. (Gary North)

The many types of wetlands include swamps, bogs, marshes, ponds, and peatlands. (Andrew Grosz)

Wetlands are commonly adjacent to dunes, such as in Indiana Dunes. (Indiana Dunes National Lakeshore)

Wetlands provide a wonderfully productive and generally safe breeding ground and home for millions of birds, mammals, reptiles, and plants. More than one-third of the 564 plant and animal species listed as threatened or endangered in the United States live in wetland habitats during some part of their lives.

Lake Michigan, the historic reason for the economic development of northern Indiana, is the result of glacial retreat about 14,000 years ago. As the glacier retreated, a series of lakes (the Great Lakes) formed, and areas of dunes and wetlands developed. In fact, there are so many wetlands at Indiana Dunes that it could just as easily have been named "Indiana Wetlands National Lakeshore." This varied topography—from wetlands to dunes—is one of the main reasons for the amazing biological diversity found in Indiana Dunes. The variation in topography, soil type, and moisture provides many niches for a variety of organisms to inhabit.

Great Marsh, in Indiana Dunes, has undergone a change in plant communities. Possibly as a result of human influence on the water levels, duckweed and cattails are now dominant. (Indiana Dunes National Lakeshore)

Indiana Dunes has many types of wetlands, including swamps, bogs, marshes, peatlands, and interdunal ponds. The type of wetland that develops in a specific location is dependent on numerous factors including the amount of water. A wetland type may change as water levels vary from season to season and year to year. Other factors determining the type of wetland include the level of dissolved oxygen, the relative acidity of the water (pH), and the amount and rate of water exchanged between the wetland and the surrounding environment. The type of wetland often determines the plant species present. Pinhook Bog is a good example. Here, species have adapted to the low mineral content, high acidity, and low oxygen levels of a wetland that has no output of water, except evaporation, and whose input of water is limited to the rain that falls directly on it. Many of the species that grow in this bog grow nowhere else in the dunes.

Wetlands are valuable because they store and purify water. Coastal wetlands are among the most biologically productive regions on Earth because they serve as the nursery area for many species. (Gary North)

This dunal pond at West Beach, in Indiana Dunes, is a rare ecosystem because it has very shallow water and a sandy bottom. It hosts a rare community of plants. (Indiana Dunes National Lakeshore)

Although the Indiana Dunes has many wetlands, a considerable number were lost or altered by humans before the establishment of the park. Since the late 1800's, wetlands have been drained or filled, and streams have been channelized to "reclaim" areas for agricultural, residential, and industrial development. Many wetlands now protected in the park need to be restored, but restoration in some areas will require the elimination of artificial drainage ditches. Unless carefully planned, their removal could impact nearby communities.

Activities outside the park have the potential to adversely affect park wetlands. Continued channelization of upstream portions of waterways outside the park can damage downstream portions within the park by increasing flow rates, flooding, streambank erosion, and siltation. Residential and agricultural developments adjacent to these same waterways could contaminate them with chemical and other residues and wastes.

The National Park Service is working to preserve and protect the valuable wetlands of the Indiana Dunes. However, as with so many other plans for resource protection at this complex park, the success of these efforts depends largely on what happens outside the park on neighboring lands.

The location of wetlands can be coastal or inland. They are frequently used as resting places and refuges for birds as they migrate seasonally. (Gary North)