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Wisconsin wetlands: acreage facts

Historic wetland acreage information in Wisconsin

The earliest information available on Wisconsin's wetlands comes from the original government land survey of the state begun in 1832 and completed in 1866. The surveyors mapped about five million acres of wetland. Although the survey gives a good distribution and extent of Wisconsin's original wetlands, it does not yield very accurate statistics. Survey methods and mapping were primitive and different surveyors had different interpretations of what constituted a wetland. Some of the work was done in the winter when wetlands were covered by ice and snow. The wetland boundaries were mapped more accurately along the Public Land Survey System (PLSS) section lines than in the interiors of the sections since the surveyors only walked the section lines. When the survey maps were drawn the land cover between the section lines was estimated.

Comparisons of the original government land survey with the Bordner Survey done in the 1930s and the USGS topographic maps (1926-1973) indicate that wetlands were frequently drawn too small on the original survey maps and some types of wetlands were overlooked.

An analysis of wet soils in Wisconsin provides us with a more accurate image of the state's original wetland acreage. Soil scientists estimate that Wisconsin has approximately 10 million acres of wet soils (somewhat poorly, poorly and very poorly drained) which is a much more accurate estimate of Wisconsin’s pre-settlement wetland acreage.

Wisconsin wetland inventory

The Wisconsin Wetland Inventory (WWI) was completed for the state in 1985. Based on aerial photography from 1978-79, it shows approximately 5.3 million acres of wetlands remaining in the state representing a loss of about 47% of original wetland acreage. This figure does not include wetlands less than 2 or 5 acres in size (minimum mapping unit varies by county) which are depicted as point symbols on the maps. Because the original WWI utilized aerial photographs taken in the summer some wetlands were missed, especially in the northern counties since interpretation was difficult due to leaf cover. Also, wetlands that were farmed as of the date of photography used and then later abandoned due to wet conditions were not captured as part of the WWI.

Wisconsin wetland inventory update program

The Legislature authorized the DNR to update the WWI on a 10-year cycle. Budget constraints and lack of staff have slowed this process to a 24-year cycle at best. Digitizing wetland maps to obtain accurate wetland acreage information is on a rotation almost twice that long. This program is underfunded and understaffed. As a result, there is no reliable qualitative and quantitative data about current rates of wetland loss.

Improvements have been made to the WWI update program. Aerial photography is now flown in the spring when leaves are off the trees. This allows for much more accurate wetland delineations. Any wetland large enough to be delineated is captured on the maps to provide for more accurate acreage information. County wetland acreage information is available for those updated counties that have been digitized. Currently, there are 18 updated counties that need to be digitized to determine wetland acreage.

Permitted wetland losses

Section 404 of the Clean Water Act establishes a program to regulate the discharge of dredged and fill material into waters of the state, including wetlands. It is the primary Federal regulatory program for wetlands. Several studies have been conducted to assess wetland loss over specific periods of time.

1970 - 1985

The Southeastern Wisconsin Regional Planning Commission (SEWRPC) has determined that regional wetland losses for the period 1970-1985 amounted to 4,010 acres. The analysis was based on interpreted aerial photography for Kenosha, Milwaukee, Ozaukee, Racine, Walworth, Washington and Waukesha Counties. Approximately 770 acres were lost between 1970-1975, 1,600 acres lost between 1975-1980 and 1,640 acres lost between 1980-1985.

1982 - August 1991

A DNR review of U.S. Army Corps of Engineers (USACE) individual permit decisions from 1982 - August 1991 shows wetland losses of approximately 10,800 acres statewide (1,200 acres/year average). Since acreage information was not available for nationwide permits during this time period, the Department analyzed recent nationwide permit decisions and determined that nationwide permit wetland losses account for approximately 1/5th the acreage lost through individual permits (2,160 acres statewide, 240 acres/year average). Combining these figures, it is estimated that approximately 12,960 acres of wetland were lost through the USACE Section 404 wetland permit program (1,440 acres/year average). These wetland acreage figures are estimates only and do not reflect total wetland loss for this time period. Wetland losses due to illegal wetland filling, wetland drainage and activities pre-authorized by general and nationwide permits are not known for this time period and it is likely that some USACE wetland permit decisions were missed during the initial review.

August 1991 - April 1998

A DNR review of USACE individual and nationwide permit decisions from August 1991 to April 1998 shows wetland losses of approximately 2,053 acres statewide (312 acres/year average). During this time period permitted wetland losses declined by 460% (1,128 acres/year average). This decline is attributed to the adoption of state wetland water quality standards on August 1, 1991. These wetland acreage figures are estimates only and do not reflect total wetland loss for this time period. Wetland losses due to illegal wetland filling, wetland drainage and activities pre-authorized by general and nationwide permits are not known for this time period and it is likely that some USACE wetland permit decisions were missed during the initial review.

Wetland restoration - acquisition - management

Wetland Reserve Program

The Wetland Reserve Program (WRP) is a voluntary program offering landowners the opportunity to receive cost-share payments for restoring wetlands on their property. The program is administered by the USDA Natural Resources Conservation Service (NRCS) and the U.S. Fish & Wildlife Service (FWS) with assistance from DNR. Recent acreage information from NRCS shows that between 1992 and April 1998, approximately 11,312 acres of wetlands have been restored and 11,312 acres of associated upland buffer protected through the WRP program. The WRP has an annual goal of restoring 10,000 acres of wetland and protecting 10,000 acres of associated upland buffer.

Conservation Reserve Program

The Conservation Reserve Program (CRP) allows the federal government to enter into contracts with agricultural producers to remove highly erodible cropland and cropped wetlands from production in return for annual rental payments per 10-year contracts. The program is administered by the Consolidated Farm Service Agency (CFSA). The FWS and DNR coordinate wetland restoration activities on these lands. Acreage figures will vary from year to year since these are not perpetual easements.

Wisconsin Department of Transportation

A statutory exemption from Chapter 30 permitting for Wisconsin Department of Transportation (DOT) projects (under 30.12(4), Wis. Stats.) required that DOT projects be reviewed under a special cooperative agreement between DOT and DNR. That agreement was amended in 1990 to include requirements for wetland compensatory mitigation for all unavoidable wetland loss due to transportation projects managed by DOT. For the period 1990 to 1997, 538 DOT projects resulted in a total wetland loss of 1,299.3 acres. To compensate for the loss, the DOT wetland banking system has developed 1903.5 acres of wetland in a combination of bank sites, off-site compensation projects and on-site compensation projects. There are 24 bank sites in the DOT system located throughout the state. It is important to note that acreage associated with wetland loss identified here may be included in acreage loss identified under "Permitted wetland losses" above.

North American Waterfowl Management Plan

The DNR Bureau of Wildlife Management has coordinated an active wetland restoration effort built around the Department’s commitment to meeting the goals and objectives of the North American Waterfowl Management Plan. The goal is to restore continental waterfowl populations to 1970s levels. Partners in this effort include state and federal agencies, private organizations and corporations. Work activities involve wetland acquisition, restoration and management. Since 1991, approximately 206,100 acres (51,525 acres of wetland, 154,575 acres of associated upland) have been secured for this purpose The goal is to acquire and restore an additional 288,750 acres (72,188 acres of wetland, 216,562 acres of associated upland) by 2012.