Terrestrial Tour: Marshes Under Threat

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Marshes and other wetlands are being restored around the world, but they are still under threat from pollutants, restricted water supply, and global climate change. 

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory.

All images, illustrations, and videos courtesy of NASA except:
·       Celtic Monster illustration by John Dickson Batten
·       Phosphate mine photo courtesy of Pamlico-Tar River Foundation, Washington, North Carolina
·       Horicon Marsh photos and marsh wildlife photos courtesy of Andrea Gianopoulos
·       Sea creature illustration copyright The National Library of Israel, Shapell Family Digitization Project _and The Hebrew University of Jerusalem, Department of Geography – Historic Cities Research Project
·       Assateague Island marsh photos courtesy of Lucy Albert
·       Muskrat photo courtesy of Dan Leveille
·       Peat fire photo courtesy of Guillermo Rein
·       Marsh algae photos courtesy of Andrea Gianopoulos
·       Close-up Lake Carnegie satellite image courtesy of the USGS EROS Data Center Satellite Systems Branch
·       Photos of Tigris River and drained Mesopotamian Marshes courtesy of Dr. Michelle Stevens, iraqmarshrestoration.blogspot.com
·       Photo of boatmen in an Iraqi marsh courtesy of Hassan Janali, U.S. Army Corps of Engineers
Music courtesy of Associated Production Music
Written by Andrea Gianopoulos
Designed by Marc Lussier

Text, marshes Under Threat
5%. Roughly 5 percent of Earth's surface holds wetlands.
Mississippi River Delta, 2005 NASA Image. These areas, where land and water blend, are found at every latitude (from the tundra to the tropics) and on every continent except Antarctica. Marshes are wetlands saturated with standing water, ranging from less than an inch to several feet deep.
Soft-stemmed plants like cattails and grasses are typical marsh plants.
You can think of marshes as flooded grasslands.
An egret, geese, ducks and a beaver. Marshes hold and support more life than any other ecosystem of the same size.
Ganges Delta, Bangladesh, 2007 NASA Image. Marshes recharge groundwater supplies and moderate stream flow, which is an especially important function during droughts.
During floods, marshes help slow water through the watershed, minimizing flood damage.
Sediment and pollutants, like nitrogen and phosphorus from fertilizers, are filtered by marshes.
Vegetation and microorganisms in the marshes can use these pollutants, improving water quality.
The benefit of marshes and other types of wetlands weren't always appreciated, and many have been destroyed.
The United States had more than 300 million acres of freshwater wetlands in 1780.
Today there are less than 100 million acres.
Most of the lost wetlands were drained for agricultural use in the early 1900s.
One of the drained wetlands was Horicon Marsh in central Wisconsin.
Farmers tried to grow onions, carrots, and potatoes there, but the heavy peat soils retained spring moisture, making it hard to grow anything.
Trying to improve their crops, farmers plowed the marsh vegetation, exposing the underlined peat.
But once the peat dried, it caught fire easily.
By 1922, peat fires dominated the area. They raged for 12 years until, in 1934, the Rock River was dammed and water began to saturate the peat again.
Today, the marsh is still being restored.
A swirl of cyanobacteria on Guatemala's Lake Atitlan. Single-celled, aquatic organisms like blue-green algae or cyanobacteria can also threaten marshes.
Cyanobacteria are toxic to humans and other animals.
They grow quickly when nutrients like phosphorus and nitrogen, which are found in fertilizers, concentrate in the still water of the marsh.
These organisms can form large colonies, creating thick mats that block sunlight from reaching the water.
The bacteria also consume the oxygen in the water, creating dead zones where other plants and animals cannot survive.
Today we realize that marshes are cradles for life, vital ecosystems for migrating waterfowl and for humans.
Marshes and other wetlands are being restored around the world, but they are still under threat from pollutants, restricted water supply, and global climate change.