Wetlands are lands that are wet for significant periods of time. They are common where water and land meet. Wetlands can be large flat areas or relatively small and steep areas.Wetlands are rich and unique ecosystems with many species that rely on both the land and the water for survival. Only specialized plants are able to grow in these conditions. Wetlands tend have a great deal of biological diversity. Wetland ecosystems can also be fragile systems that are sensitive to the amounts and quality of water present within them.
Types of Wetlands
There are a variety of different types of wetlands. Marshes are shallow wetlands around lakes, streams, or the ocean where grasses and reeds are common, but trees are not. Frogs, turtles, muskrats, and many varieties of birds are at home in marshes.
A swamp is a wetland with lush trees and vines found in a low-lying area beside slow-moving rivers. Like marshes, they are frequently or always inundated with water. Since the water in a swamp moves slowly, oxygen in the water is often scarce. Swamp plants and animals must be adapted for these low-oxygen conditions. Like marshes, swamps can be fresh water, salt water, or a mixture of both.
In an estuary, salt water from the sea mixes with fresh water from a stream or river. These semi-enclosed areas are home to plants and animals that can tolerate the sharp changes in salt content that the constant motion and mixing of waters creates. Estuaries contain brackish water, water that has more salt than fresh water but less than seawater. Because of the rapid changes in salt content, estuaries have many different habitats for plants and animals and extremely high biodiversity.
Ecological Role of Wetlands
As mentioned above, wetlands are home to many different species of organisms. Although they make up only 5 percent of the area of the United States, wetlands contain more than 30 percent of the plant types. Many endangered species live in wetlands, so wetlands are protected from human use. Wetlands also offer protection from storm surges from tropical storm systems like hurricanes and provide safe, hidden protection for hatchlings.
Wetlands also play a key biological role by removing pollutants from water. For example, they can trap and use fertilizer that has washed off a farmer’s field, and therefore they prevent that fertilizer from contaminating another body of water. Since wetlands naturally purify water, preserving wetlands also helps to maintain clean supplies of water.