The Life Cycle of Wetlands

Seasonal Changes Back to Top

Each individual wetland changes differently. Some wetlands go through seasonal changes. These wetlands would be dry during drought seasons, mostly summer and winter, and wet during seasons of heavy rainfall, like fall and spring. Wetlands change depending on the weather in their locations. Some wetlands go through much longer stages, often over several years.  


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How Are Wetlands Created? Back to Top

Wetlands can be formed in a few different ways. They are formed naturally from the overflowing of bodies of water such as rivers or lakes, or sometimes even ocean water. Many wetlands were formed by the last ice age, when glaciers formed indentations in the ground that eventually held shallow amounts of water and turned into wetlands.  Wetlands can also be formed by succession.



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The Water Cycle Back to Top

Water, water everywhere!

Every school child draws the water cycle: water evaporating from the sea, then blown inland, forming clouds that rain down to journey back to the sea.

This is no small issue. Planet-wide, something on the order of 10 million billion gallons of water are transported through the water cycle each year. (That's a one with 16 zeros behind.)

But there's more to that simplistic view we remember from childhood. The water cycle involves the soil, plants, and animals–including us. This life-giving circle is better viewed as a complex three-dimensional circuit with nearly infinite branches and off-shoots that involves most of the atmosphere and the upper levels of earth's crust.

Probably the most complex section of the water cycle is what happens when the rain (or snow, or hail, or sleet) reaches the ground. Certainly, much of it runs off our trees and roofs and down our hills and sidewalks. But quite a bit of it–usually most of it–soaks into the ground.

Under the surface, the water binds itself to the soil particles until the soil is saturated. Or until a plant takes it up. The water picked up by plant roots is either chemically converted into more plant or is passed through the leaves back into the air.

Water is pulled deeper underground until it meets a barrier. The water collects above of the barrier; the "water table" is the top of that layer of water.

Rivers, streams, and lakes are not just "where the water collects on the land," they're usually more accurately described as "where the water table breaks through the surface."

Wetlands occur where the water table is at or near the surface. Long thought to be "wastelands," we now know wetlands perform many vital functions. The life and chemistry of wetland soils clean impurities out of the water. Wetland soils–and the wetland's position in the cycle–collect and hold floodwaters, then slowly disperses them. Wetlands along the edges of open waters buffer the shoreline from erosion. Wetlands produce and recycle huge amounts of plant and animal life, much of which is passed on to adjacent land and water habitats. Further, rich wetland ecosystems are critical permanent or nursery habitat for myriad species of plants and animals.


How Animals are Affected by the Life Cycle of the Wetlands Back to Top

As the state's population of 11.3 million (2000) continues to grow, projected changes in rainfall, evaportion, and groundwater recharge rates will affect all freshwater users in the state. Reduced summer water levels are likely to diminish the recharge of groundwater, cause streams to dry up, and reduce the area of wetlands, resulting in poorer water quality and less habitat for wildlife.



For ducks, geese and other migratory birds, wetlands are the most important part of the migratory cycle, providing food, resting places and seasonal habitats. Some of these birds use wetlands as a breeding ground, coming back every spring to mate and produce offspring.

Fish and Wildlife Habitats Back to Top

More than one-third of the United States' threatened and endangered species live only in wetlands, and nearly half use wetlands at some point in their lives. Many other animals and plants depend on wetlands for survival. Estuarine and marine fish and shellfish, various birds, and certain mammals must have coastal wetlands to survive. Most commercial and game fish breed and raise their young in coastal marshes and estuaries. Menhaden, flounder, sea trout, spot, croaker, and striped bass are among the more familiar fish that depend on coastal wetlands. Shrimp, oysters, clams, and blue and Dungeness crabs likewise need these wetlands for food, shelter, and breeding grounds. For many animals and plants, like wood ducks, muskrat, cattails, and swamp rose, inland wetlands are the only places they can live. Beavers may actually create their own wetlands. For others, such as striped bass, peregrine falcon, otter, black bear, raccoon, and deer, wetlands provide important food, water, or shelter. Many of the U.S. breeding bird populations-- including ducks, geese, woodpeckers, hawks, wading birds, and many song-birds-- feed, nest, and raise their young in wetlands. Migratory waterfowl use coastal and inland wetlands as resting, feeding, breeding, or nesting grounds for at least part of the year. Indeed, an international agreement to protect wetlands of international importance was developed because some species of migratory birds are completely dependent on certain wetlands and would become extinct if those wetlands were destroyed.

(Reference: U.S. Environmental Protection Agency. 1995b. America's wetlands: Our vital link between land and water. Office of Water, Office of Wetlands, Oceans and Watersheds. EPA843-K-95-001)

Animal Habitats Back to Top

Wetlands sustain more life than almost any other ecosystem, even though only about 6% of the earth's surface is wetland. Wetland animals have developed adaptations of all kinds to allow them to cope with life where water is so critical. At the same time, because of historical attitudes towards wetlands, many endangered animals are precisely those which depend to a great extent on the watery environment.

Some animals living in wetlands include:

  • Dragonflies
  • Damselflies
  • Water Bugs
  • Beetles
  • Crayfish
  • Scuds
  • Snails
  • Leeches
  • Bluegill
  • Bass
  • Catfish
  • Snakes
  • Turtles
  • Frogs
  • Great Blue Herons
  • Ducks


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