|
|
Home
> Environment
>
Land Resources and Conservation
>
COASTLINES AND ESTUARIES
COASTLINES AND
ESTUARIES
Estuaries are coastal
bodies of water that connect to oceans; they include tidal marshes and
tidal rivers. In estuaries, fresh water from the land mixes with salt
water from the oceans, resulting in high productivity. Many ocean fish
and shellfish spend all or portions of their lives in estuaries,
supported by the many producers, which range from microscopic algae to
seaweeds and marsh grasses. Coastal estuaries, which provide food and
protective habitat, could be considered the ocean's nurseries because so
many different marine organisms spend the first parts of their lives
there.
|
Historically, coastal wetlands (also
called saltwater wetlands) have been regarded as wasteland, good
only for breeding large populations of mosquitoes. Coastal wetlands
throughout the world have been drained, filled in, of dredged out to
turn them into "productive" structures such as industrial parks or
marinas. In the United States, people have belatedly recognized the
importance of coastal wetlands and have passed legislation to slow
their destruction. (See Meeting the Challenge: The Montezuma
Wetlands Project for a description of a wetlands restoration
project.) |
|
The Coastal Barrier Resources Act of 1982
abolished most federal assistance programs, including federal flood
insurance, for new development ventures on undeveloped coastal barriers.
This law has helped to eliminate some of the contradictions in
governmental policies regarding coastal wetlands.
Mangrove Swamps
Most of the shoreline in the tropics
consists of densely vegetated wetlands called mangrove swamps.
Mangroves—certain trees and shrubs that require salty water—grow best in
the intertidal zone, where they are alternately submerged to their
trunks at high tide and exposed to their roots at low tide.
Mangroves help to build soil along the
shoreline by holding sediments in place. In some places, as the soil
accumulates, other plants invade the area and the mangroves continue
their slow expansion into the ocean. Mangrove roots provide habitat
for oysters, fiddler crabs, and other marine organisms, and mangrove
branches provide nesting sites for many shorebirds. Mangrove swamps are
often destroyed to provide firewood, space for coastal development, and
agriculture land.
|
