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Wetlands 2007

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2007 NRI Wetlands (PDF; 1.5 MB)

Land Use | Development | Erosion | Wetlands
About the Data | Glossary | Index of Tables

The National Resources Inventory (NRI) is a statistical survey of natural resource conditions and trends on non-Federal land in the United States. Non-Federal lands include privately owned lands, tribal and trust lands, and lands controlled by state and local governments.

The NRI provides nationally consistent statistical data on wetlands and deepwater habitats, including changes in extent of these areas between 1992 and 2007. To assess conservation issues, this information must be analyzed in conjunction with other NRI data elements.

Wetland ecosystems provide diverse services vital for environmental well-being, including food and habitat for wildlife and supporting and regulating services -- such as nutrient cycling, delivery of fresh water, groundwater recharge, and mitigation of flooding. Wetlands also have significant aesthetic, educational, and cultural values and provide opportunities for recreation and tourism.

The findings presented here cover Palustrine and Estuarine wetlands and other aquatic habitats for the period 1992 to 2007 for the conterminous 48 States. Estimates do not include wetlands in Alaska, Hawaii, Puerto Rico, or on Federal lands. The NRI provides information on systems and classes of wetlands, regional distributions, and associated factors such as soils and land use. Of particular interest are trends in wetland gains and losses due to agricultural activities.

The Cowardin et al. (1979) classification system recognizes five systems of wetlands and deepwater habitats. While there is a wetland component in each of those Cowardin systems, these results do not include estimates for wetlands in Marine, Lacustrine, and Riverine systems unless specifically identified separately as such. Estuarine wetlands are tidal wetlands that are usually semienclosed by land, but have open, partly obstructed, or sporadic access to the open ocean, and in which ocean water is at least occasionally diluted by freshwater runoff from the land. Palustrine wetlands include nontidal wetlands dominated by trees, shrubs, persistent emergent plants, or emergent mosses or lichens, as well as small, shallow open water ponds or potholes. Palustrine wetlands are often called swamps, marshes, potholes, bogs, or fens.

For more information, see (Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U. S. Department of the Interior, Fish and Wildlife Service, Washington, D.C).

Key Findings

  • Palustrine and Estuarine wetlands covered 7 percent of the water and non-Federal land area of the conterminous 48 States in 2007, accounting for nearly 111 million acres. (Table 6)
  • In 2007, Minnesota and Louisiana had the highest acreage of Palustrine and Estuarine wetlands. Minnesota had 10.9 million acres (all Palustrine) and Louisiana had 10.2 million acres (7.7 million acres Palustrine; 2.5 million acres Estuarine). (Table 1)
Map of 

Palustrine and Estuarine wetlands on water areas and non-Federal land

Source: Table 1

  • In 2007, there were 105.3 million acres of Palustrine wetlands and 5.4 million acres of Estuarine wetlands in the conterminous 48 States. Deepwater habitats, made up of Lacustrine, Estuarine deepwater, Riverine, and Marine habitat systems, totaled 48.5 million acres. (Table 1)
Pie chart of wetlands by type

Source: Table 1

  • Approximately 66 million acres, 60 percent of Palustrine and Estuarine wetlands, occurred on forest land in 2007. Slightly less than 17 million acres, or 15 percent, occurred on cropland, pastureland, and Conservation Reserve Program (CRP) land. (Table 2)
Pie chart of Palustrine and Estuarine wetlands on water areas and non-Federal 

land

Source: Table 2

  • Most states mirrored this composition with Maine and North Carolina having the highest percentage of their States' wetlands in forest land in 2007. (Table 2)
  • Three States had over 50 percent of their 2007 wetlands in cropland, pastureland, and CRP land: Idaho, Kansas, and Iowa. (Table 2)
  • Most wetlands occurred in the eastern half of the United States, particularly in the Lake States, Southeast, and Delta States regions. (Table 3)
  • In 2007, most Farm Production Regions had more wetlands in forest land than in other land uses. The exceptions were the Northern Plains and Pacific regions, which had more wetland acreage in cropland, pastureland, and CRP land; and the Mountain region, which had more wetland acreage in rangeland. (Table 4)
Map of Palustrine and Estuarine wetlands by Farm Production Region, 2007

Source: Table 4

  • Most Palustrine wetlands are vegetated, 94.8 million acres in 2007. Of these, 68.8 million acres are dominated by trees or shrubs (forested and scrub-shrub) and 26.0 million acres are dominated by herbaceous vegetation (emergent). (Table 5)
  • In 2007, approximately 10.5 million acres of wetlands were freshwater open wetlands without emergent vegetation (Palustrine other) and almost 5.4 million acres were brackish water wetlands (Estuarine). (Table 5)
Pie chart of Palustrine and Estuarine wetlands in 2007 by Cowardin System

Source: Table 5

  • Although the acreage of Palustrine and Estuarine wetlands declined from 1992 to 1997, during the two 5-year periods from 1997 to 2002 and 2002 to 2007 gross gains to wetlands were greater than gross losses. Although there was a net increase in wetlands from 1997 to 2002, the net change from 2002 to 2007 was not significant at the 95 percent confidence level. See Margins of Error for more information. (Table 6 and Table 10)
Bar chart of losses and gains in Palustrine and Estuarine wetlands

Source: Table 10

  • For the period 1992 to 1997, Palustrine and Estuarine wetlands had a 326,100 acre gain from uplands. This was offset by a 482,400 acre loss to uplands, resulting in a net loss of 156,300 acres. (Table 10)
  • For the period 1997 to 2002, Palustrine and Estuarine wetlands had a 395,800 acre gain from uplands. This was offset by a 247,000 acre loss to uplands, resulting in a net gain of 148,800 acres. (Table 10)
  • For the period 2002 to 2007, Palustrine and Estuarine wetlands had a 295,500 acre gain from uplands. This was offset by a 194,100 acre loss to uplands. The net change is not significant, however, at the 95 percent confidence level. See Margins of Error for more information. (Table 10)
  • For both 5-year periods 1997 to 2002 and 2002 to 2007, gross gains to wetlands from agricultural lands were greater than gross losses from wetlands on agricultural land. Conversely, gross losses of wetlands to development were greater than gross gains. (Table 10)
  • The two 5-year periods 1997 to 2002 and 2002 to 2007, also showed net gains to wetlands from other than agricultural or development. (Table 10)
Bar chart of losses and gains in Palustrine and Estuarine wetlands by reason

Source: Table 10

  • The decade from 1997 to 2007 was the first decade in modern history in which a net gain in wetlands was documented. There was an average annual gain in wetlands of 25,000 acres during this decade. (Table 15)
  • During the 1997 to 2007 period, gross gains to wetlands totaled 691,100 acres. Most of these gains, 410,200 acres, or 59.4 percent, were from agricultural lands. Only 15,200 acres, or 2.2 percent, occurred on developed lands. (Table 15)
  • Development was the major cause of wetland loss during the 1997 to 2007 period. Of the 441,100 acres of gross losses, 266,000 acres, or 60 percent, were lost to development. (Table 15)
  • The conterminous United States. has 242 coastal counties and 2,870 inland counties. Although coastal counties represent only 7 percent of the surface area of the United States and 20 percent of the Palustrine and Estuarine wetlands, they accounted for 30 to 39 percent of the wetland losses during the 1992 to 2007 period. (Table 10, Table 11 and Table 13)
  • Coastal counties have 100 percent of the Estuarine wetlands. Most coastal Palustrine wetlands are dominated by trees or shrubs (forested and scrub-shrub). (Table 12)
Map of coastal counties in the continental United States
  • Gross wetland losses in coastal counties decreased between 1992 and 2007, but gross gains were not enough to offset the losses. Therefore, coastal counties showed a net loss in each 5-year period since 1992: 116,100 acres from 1992 to 1997, 65,100 acres from 1997 to 2002, and 56,100 acres from 2002 to 2007. (Table 13)
  • For the period 1997 to 2007, most of the wetland losses in coastal counties were due to development: 84,900 acres from 1997 to 2002 and 45,600 acres from 2002 to 2007. (Table 13)
Bar chart of losses and gains in Palustrine and Estuarine wetlands, coastal counties

Source: Table 13

  • Gross wetland losses in inland counties also decreased during the 1992 to 2007 period. Gross wetland gains increased from 1997 to 2002 but then decreased from 2002 to 2007. (Table 14)
  • Inland counties showed a net wetland loss from 1992 to 1997 (40,200 acres) but net wetland gains from 1997 to 2002 (213,900 acres) and from 2002 to 2007 (157,500 acres). (Table 14)
  • Similar to coastal counties, most of the wetland losses in the inland counties were due to development, but to a lesser extent: 75,700 acres from 1997 to 2002 and 59,800 acres from 2002 to 2007. (Table 14)
  • For the period 1997 to 2007, most of the wetland gains in the inland counties were due to agriculture: 211,600 acres from 1997 to 2002 and 174,500 acres from 2002 to 2007. (Table 14)
Bar chart of losses and gains in Palustrine and Estuarine wetlands, inland counties

Source: Table 14

  • From 1997 to 2007, there was a net loss of 121,400 acres in the coastal counties and a net gain of 371,400 acres in the inland counties. (Table 15)
Bar chart of losses and gains in Palustrine and Estuarine wetlands, 1997 to 2007

Source: Table 15

  • Development resulted in the loss of 135,500 acres in the inland counties from 1997 to 2007 and 130,500 acres in the coastal counties. (Table 15)
  • During the 10-year period 1997 to 2007, development was responsible for 76 percent of the wetland losses in the coastal counties and 50 percent in the inland counties. Agriculture was responsible for only 6 percent of the wetland losses in the coastal counties and 21 percent of the losses in the inland counties. (Table 15)
Bar chart of Losses in Palustrine and Estuarine wetlands by Reason, Coastal and Incland Counties, 1997 to 2007

Source: Table 15

Tabular Results

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