Minnesota Wetland Report
IX. Wetland Numbers for Minnesota
many and what types of wetlands do we have and where are they?
Anderson & Craig (Growing Energy Crops on Minnesotas
Wetlands: The Land Use Perspective, 1984) determined that there
are 8.8 million acres of wetlands in Minnesota, compared to 18.6
million acres of original wetlands (see Appendix I1).
The amount of original wetlands is based on 1969 Land Use and
Soils Data using 40 acre parcels.
Although this study is dated, it remains the only statewide
estimate of original vs. remaining wetlands.
The National Wetland Inventory (NWI) maps include all waters and
wetlands and rivers that have measurable area.
The NWI summary indicates approximately 10.6 million acres of
wetlands currently exist in Minnesota (excluding water areas deeper
than two meters). Appendix
I2 shows the distribution of wetland types across the state.
Most of this data was mapped during the period from 1982
through 1993 based on aerial photography done from 1974 through
1984. The NWI maps
exclude some farmed wetlands and may contain inaccuracies because of
land use changes since they were developed.
Also, there are mistakes inherent when identifying certain
types of wetlands with remote sensing methods.
Nonetheless, the NWI is the best and most current statewide
data available for existing wetlands.
Digitization of the NWI data has been recently completed and
information on obtaining versions of the NWI maps can be obtained by
calling 1-800-USA-MAPS or on the Internet at http://www.nwi.fws.gov.
Paper copies of the NWI maps can be purchased from the
Minnesota Bookstore by calling 1-800-657-3757 or 651-297-3000.
The Natural Resource Conservation Service has developed the National
Resources Inventory (NRI), which is based on field sampling.
This study or inventory, which includes farmed wetlands,
concluded from 1992 data that a total of approximately 10.6 million
acres of wetlands (and 3.6 million acres of water areas deeper than
two meters) remain in Minnesota, compared to an original number of
20+ million acres of wetlands.
The NRI data represents a statistical model that is accurate
only at a very large scale and is not useful for field work or local
planning efforts. The
NRI can be accessed on the Internet at http://www.mn.nrcs.usda.gov.
Minnesota Board of Water and Soil