Wetlands - Status and Trends
The lower 48 states contained an estimated 110.1 million acres of wetlands in 2009.1 This is an area about the size of California. In 1994, an estimated 174 million acres of wetland existed in Alaska2-- covering nearly half of the state-- while Hawaii had 52,000 acres as of the 1980s.3 Next to Alaska, Florida (11.4 million),4 Minnesota (10.6 million),5 Louisiana (7.8 million),6 and Texas (7.6 million)7 have the largest wetland acreage.
In the 1600s, over 220 million acres of wetlands are thought to have existed in the lower 48 states.8 Since then, extensive losses have occurred, and over half of our original wetlands in the lower 48 have been drained and converted to other uses.9 The years from the mid-1950s to the mid- 1970s were a time of major wetland loss, but since then the rate of loss has decreased.
Between 2004 and 2009, an estimated 62,300 acres of wetlands were lost in the conterminous United States.10 Various factors have contributed to the decline in the loss rate including implementation and enforcement of wetland protection measures and elimination of some incentives for wetland drainage. Public education and outreach about the value and functions of wetlands, private land initiatives, coastal monitoring and protection programs, and wetland restoration and creation actions have also helped reduce overall wetland losses.
These losses, as well as degradation, have greatly diminished our nation's wetlands resources; as a result, we no longer have the benefits they provided. The increase in flood damages, drought damages, and the declining bird populations are, in part, the result of wetlands degradation and destruction.
Wetlands have been degraded in ways that are not as obvious as direct physical destruction or degradation. Other threats have included chemical contamination, excess nutrients, and sediment from air and water. Global climate change could affect wetlands through increased air temperature; shifts in precipitation; increased frequency of storms, droughts, and floods; increased atmospheric carbon dioxide concentration; and sea level rise. All of these impacts could affect species composition and wetland functions.
Major Causes of Wetland Loss and Degradation
- Dredging and stream channelization
- Deposition of fill material
- Diking and damming
- Tilling for crop production
- Air and water pollutants
- Changing nutrient levels
- Releasing toxic chemicals
- Introducing nonnative species
- Grazing by domestic animals
- Sea level rise
- Hurricanes and other storms
- Wetlands Status and Trends Reports: The U.S. Fish and Wildlife Service publishes a variety of national, state, and regional reports to track and estimate the status and trends of wetland extent in the United States.
- National Resources Inventory: The NRI is conducted by the U.S. Department of Agriculture's Natural Resources Conservation Service, in cooperation with the Iowa State University Statistical Laboratory. The NRI is a statistical survey of land use and natural resource conditions and trends on U.S. non-Federal lands, including wetlands.
- Dahl, T.E. 2011. Status and Trends of Wetlands in the Conterminous United States 2004 to 2009. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 108 pp. http://www.fws.gov/wetlands/Status-And-Trends-2009/index.html.
- Hall, Jonathan V., W.E. Frayer, and Bill O. Wilen. 1994. Status of Alaska Wetlands. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 36 pp. http://www.fws.gov/wetlands/Documents/Status-of-Alaska-Wetlands.pdf. (PDF) (36 pp, 5.5 MB)
- Dahl, T.E. 1990. Wetlands Losses in the United States 1780's to 1980's. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 13 pp. http://www.fws.gov/wetlands/Documents/Wetlands-Losses-in-the-United-States-1780s-to-1980s.pdf. (PDF) (20 pp, 2.3 MB)
- Dahl, T.E. 2005. Florida's Wetlands: An Update on Status and Trends 1985 to 1996. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 80 pp. http://www.fws.gov/wetlands/Documents/Floridas-Wetlands-An-Update-on-Status-and-Trends-1985-to-1996.pdf. (PDF) (83 pp, 16.3 MB)
- Klobier, Steven M. 2010. Status and Trends of Wetlands in Minnesota: Wetland Quantity Baseline. Minnesota Department of Natural Resources. Ecological and Water Resources Report, Saint Paul, MN. 28 pp. http://files.dnr.state.mn.us/eco/wetlands/wstmp_report_final_121410.pdf. (PDF) (28 pp, 1.5MB)
- Caffey, R.H. and M. Schexnayder. 2003. "Coastal Louisiana and South Florida: A Comparative Wetland Inventory," Interpretive Topic Series on Coastal Wetland Restoration in Louisiana, Coastal Wetland Planning, Protection, and Restoration Act (eds.), National Sea Grant Library. 8 pp. http://lacoast.gov/new/Data/Reports/ITS/Florida.pdf. (PDF) (8 pp, 704K)
- Dahl 1990.
- Dahl 2011.