What are wetlands?

Wetlands are transitional areas, sandwiched between permanently flooded deepwater environments and well-drained uplands, where the water table is usually at or near the surface or the land is covered by shallow water. They include mangroves, marshes (salt, brackish, intermediate, and fresh), swamps, forested wetlands, bogs, wet prairies, prairie potholes, and vernal pools. In general terms, wetlands are lands where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface. The single feature that most wetlands share is soil or substrate that is at least periodically saturated with or covered by water.

Learn more: USGS Wetland and Aquatic Research Center

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What are the long-term effects of climate change?

Scientists have predicted that long-term effects of climate change will include a decrease in sea ice and an increase in permafrost thawing, an increase in heat waves and heavy precipitation, and decreased water resources in semi-arid regions. Below are some of the regional impacts of global change forecast by the Intergovernmental Panel on...

How would sea level change if all glaciers melted?

There is still some uncertainty about the full volume of glaciers and ice caps on Earth, but if all of them were to melt, global sea level would rise approximately 70 meters (approximately 230 feet), flooding every coastal city on the planet. Learn more: USGS Water Science School: Glaciers and Icecaps National Snow and Ice Data Center: Facts about...

Why are wetlands important?

Wetlands provide habitat for thousands of species of aquatic and terrestrial plants and animals. Wetlands are valuable for flood protection, water quality improvement, shoreline erosion control, natural products, recreation, and aesthetics. Wetlands are among the most productive habitats on earth providing shelter and nursery areas for...

What is the Brown Marsh phenomenon?

Sudden marsh dieback events are not uncommon and have occurred in coastal marshes from the Gulf of Mexico to Maine. Brown Marsh is a term given to the unusually rapid and extensive browning of Louisiana’s saltwater marsh grass Spartina alterniflora, commonly known as oyster grass or smooth cordgrass. One of the most severe events occurred in 2000...
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Date published: January 25, 2017

Changes in Rainfall, Temperature Expected to Transform Coastal Wetlands This Century

Changes in rainfall and temperature are predicted to transform wetlands in the Gulf of Mexico and around the world within the century, a new study from the USGS and the University of Texas Rio Grande Valley concludes.

Date published: January 24, 2017

New Technique Quickly Predicts Salt Marsh Vulnerability

If coastal salt marshes are like savings accounts, with sediment as the principal, all eight Atlantic and Pacific coast salt marshes studied are "in the red," researchers found.

Date published: December 21, 2015

Normal Weather Drives Salt Marsh Erosion

For salt marshes, hurricanes are just another day at the beach.

Attribution: Natural Hazards
Date published: July 15, 2015

Drainage of Prairie Pothole Wetlands Can Increase Flooding and Degrade Ecosystems

The drainage of small wetlands can decrease wildlife habitat and may contribute to flooding in the Prairie Pothole Region (PPR), according to a recent U.S. Geological Survey study.

Date published: July 17, 2013

Connectivity Best for Created Wetlands

New research by the U.S. Geological Survey has found that many wetlands created for habitat do very little to improve water quality problems in streams and rivers. Collectively, these wetland design practices represent a missed opportunity to improve the general ecological health of watersheds and wetland ecosystems. 

Date published: April 29, 2013

Rising Seas Could Threaten Many Acadia NP Marshes

More than 800 acres of uplands in and near Acadia National Park will likely be flooded by the ocean if sea level rises 2 feet during this century, leaving 75 percent of the saltwater marshes along this part of central Maine's rugged coast with very little upland area to migrate into, according to a new U.S. Geological Survey study and maps.

Date published: May 28, 1998

Climate Change May Affect the Carbon Balance of a Rocky Mountain Wetland

BOSTON--The carbon balance of wetlands in the southern Rocky Mountains may be very sensitive to small changes in local climate, according to recent research conducted by the U.S. Geological Survey.

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White Heron in Marsh
June 30, 2017

White Heron in Marsh

A white heron flying across a marsh in York County, Virginia.

WERC sunset over salt marsh wetland
June 23, 2017

WERC sunset over salt marsh wetland

Sunset over salt marsh wetland

Phragmites under stress in Pass A Loutre, Louisiana
May 31, 2017

High stakes, big questions in marsh grass die-back

Brown patches and brown stems show stress in this phagmites (roseau cane) stand in Pass A Loutre Wildlife Management Area, a tract of state-owned land in Louisiana's bird foot delta, where the Mississippi River meets the Gulf of Mexico. An ongoing phragmites was first discovered in spring 2017 and blamed on an invasive scale insect from Asia. But a new USGS report, based

Photo of former USGS employee Kat Powelson measuring marsh accretion.
February 7, 2017

WERC Employee Measuring Marsh Accretion

A photo of former USGS employee (current U.S. Fish and Wildlife Service employee) Kat Powelson measuring accretion in a southern California wetland.

New England Salt Marsh
January 30, 2017

New England Salt Marsh

High marsh vegetation at Wertheim National Wildlife Refuge

Nutria in Louisiana wetlands
September 23, 2016

Nutria in Louisiana wetlands

Nutria in Louisiana wetlands

June 30, 2016

Mercury and Rice in the California Delta: Lessons Linking Wetlands to Water to Wildlife

  • Wetlands are hotspots for mercury methylation and export of methylmercury to aquatic foodwebs.
  • Rice is the most abundant wetland type in California and globally in temperate and tropical latitudes.
  • Physical, chemical and biological Hg transformations are temporally pulsed in agricultural wetlands, due largely to seasonal water management practices.
Wetland Restoration; Wetland Marsh Restored
December 31, 2013

Wetland Marsh Restored

Wetland restoration, weland restored

May 31, 2012

PubTalk 5/2012 — Restoring the Wild Heart of South San Francisco Bay

--The South Bay Salt Pond Restoration Project

By Laura Valoppi, Lead Scientist


  • This is largest Western U.S. coastal wetlands restoration project, encompassing 15,100 acres of former salt ponds around the edge of South San Francisco Bay
  • The project will restore and enhance South Bay wetlands for endangered