Chapter: Freshwater at Earth’s Surface Table of Contents Section 3: Wetlands Section 1: Streams Section 2: Lakes and Reservoirs Section 4: Pollution of Freshwater
Types of Wetlands
Wetlands are areas of land that are covered with water during some part of the year.
Biologists recognize wetlands by the types of plants that grow there.
Types of wetlands include swamps, marshes, and bogs and are defined primarily by their vegetation.
Swamps are wetlands where the most common types of plants are trees and shrubs.
Swamps need a steady supply of water in order for wetlands trees to grow.
They often are found in low-lying areas near rivers, where water is slow moving.
A marsh is a type of wetland that doesn’t have many trees or shrubs.
Marshes often form on floodplains where rivers overflow their banks.
They also form at the edges of lakes where the shoreline slopes gently.
Most bogs formed in depressions that were created by glaciers.
Rain is the only source of freshwater in a bog.
Because no streams enter a bog to bring in nutrients, plants have developed unique ways to get them.
Bogs Wetlands 3
Some plants, such as pitcher plants and the Venus’s-flytrap get their nutrients from insects.
Water doesn’t drain from a bog, so dead material builds up.
Dead plants sink to the bottom and might eventually form a substance called peat.
Most of the peat that is used by gardeners comes from a plant called sphagnum moss.
This plant, when dried, can hold as much as 20 times its weight in water.
Because wetlands are found along the edge between water and land, they provide a habitat for water and land animals.
Wetlands are important for migrating birds.
They provide cover and resting areas between long flights, as well as plenty of small insects, fish, and plants to feed on.
Animals such as mink and muskrat live in wetlands.
The beaver, makes its own wetlands by damming up a stream if no wetlands are around.
Wetlands also are home to a variety of reptiles, such as alligators, turtles, and snakes.
Amphibians, such as salamanders and frogs, also live in wetlands.
Many of these animals need the shallow water of wetlands to nest and reproduce.
Importance of Wetlands
Today, wetlands are recognized as a valuable resource.
Wetlands act as a natural sponge, soaking up excess water from rain, melting snow, and floods and then slowly releasing it.
Wetlands near lakes and rivers help protect shorelines and stream banks against erosion because plant roots help hold soil in place and slow the speed of moving water.
Wetlands, such as those found on floodplains and deltas, are especially effective at trapping sediment because their vegetation slows the water’s flow.
Trapped sediment cannot enter the lake or stream, so the water remains clear.
Fish, their eggs, and plant life all thrive in clear water.
Wetland plants also use nutrients for growth, slowing the rate of eutrophication.
Lakes and streams that have large wetland areas generally have better water quality because wetlands remove nutrients from the water.
Human wastewater, called sewage, contains high amounts of nutrients.
In most cities, the wastewater is treated at a sewage-treatment facility to remove pollutants.
The water then is released into a river or other water body.
Wetlands are so effective at removing nutrients that they sometimes are created at sewage-treatment facilities to treat sewage.
Section Check 3 Question 1 Which are used to classify wetlands as marshes, swamps, or bogs? A. nutrients B. the amount of water in the area C. types of organisms living there D. types of vegetation growing there NC: 3.02
Section Check 3 Answer The answer is D. Wetlands are defined by their vegetation. NC: 3.02
Section Check 3 Question 2 What type of wetlands formed in depressions that were created by glaciers? A. bog B. man-made C. marsh D. swamp NC: 3.02
Section Check 3 Answer The answer is A. The only source of freshwater for bogs is rain. NC: 3.02
Section Check 3 Question 3 List some reasons why wetlands are an important resource. NC: 3.07
Section Check 3 Answer Wetlands act as a natural sponge, soaking up excess water from rain, melting snow, and floods and then slowly releasing it. They help protect shorelines and stream banks against erosion because plant roots slow the speed of water. Wetlands also slow the rate of eutrophication because their plant roots take up excess nutrients. NC: 3.07