are communities. Each community is made of the land, climate and the plants
and animals these support. Each time Iowa’s land or climate has changed,
its habitats have changed as well. The plants and animals best suited to the
new conditions take over. The others die or are pushed into small areas. Most
of these changes have taken thousands or millions of years to occur.
Iowa’s habitats have changed drastically in the past 200 years. However, these changes are not because of a change in the land or climate.
A Change of Habitats
Fossil records show that for long
periods of time, a shallow sea covered Iowa. Coral reef, sharks and ancient
animals all called the area home. Coal deposits in parts of Iowa are evidence
of an ancient subtropical swamp environment. Coniferous forests covered Iowa
between the times the land was covered by glaciers.
After the most recent glaciers retreated, the climate warmed. Plants and animals more suited to the warmer, drier climate thrived. First, broadleaf trees replaced most of the conifers. Then prairie grasses replaced most of the broadleaf trees. The animal communities changed as the plants did.
The Mississippi and other Iowa rivers
have long been used as transportation routes. In 1673 Father Jacques Marquette
and Louis Joliet traveled along the Mississippi River exploring the east "coast"
of Iowa. Rivers and riverbanks are also habitat for fish, insects, water plants,
amphibians, beaver, otter and many other animals. Iowa has 71,665 miles of
rivers and streams, making it an important habitat.
Growing along the rivers are woodlands. In order to survive trees need the cooler temperatures, the water, and the lower wind speeds that these areas provide. Silver maple, cottonwood and willow forests are found along the rivers' edges and in floodplains. Oak and hickory forests are more common on the higher banks. Iowa forests were the first area explorers and settlers were interested in. They were familiar with forest animals and plants. Trees provided fuel and lumber. Deer and beaver provided food and furs. And forests felt safer, more like home. In the early 1800s, almost 19 percent of Iowa was covered in forest.
Past the protected river valleys the climate was hotter, drier and windier. Here, the dominant habitat was prairie. Prairie grasses and flowers stretched as far as the eye could see. Around 70 percent of Iowa was prairie. Over 100 types of prairie grasses and wildflowers rippled across the hills and valleys. Prairie plants grow deep roots. Deep roots are effective at obtaining water, holding the soil in place, and discouraging trees from taking root. These grasses also easily sprout again after a wildfire roars over them. The plants provide food and shelter for many animals. Bison, elk and wolves once roamed freely across the grasslands. Prairie chickens, passenger pigeons and bobolinks were common birds. Butterflies and other insects were thick. This habitat was strange and scary.
Tucked in places where water could collect, there are wetlands. Glaciers created the numerous shallow prairie marshes in north central Iowa. These soggy depressions usually hold water for only part of the year. Flooding and channel cutting created backwater wetlands along the rivers and streams. Lakes, marshes, bogs and fens dot small areas of the landscape. Many of these wetlands hold water year round. They provide flood and pollution control. They are important stopover and breeding places for ducks, geese and shorebirds. Muskrat, otter, herons, cranes and many other animals are also wetland residents. Mosquitoes also love these areas. For the most part, explorers did not. In 1800 wetlands covered almost 11 percent of Iowa.
If early explorers returned to Iowa today, they would not recognize it. Less than ten percent of the land looks the same. The rest has been changed.
Native Americans had long used the
bounty of Iowa’s habitats for their survival. However, they did not
make major changes to the natural communities. When European settlers migrated
into the state in the 1800s, they started modifying the habitats to meet their
Many people chose to settle near rivers and streams. To make farming and development easier, people dug trenches to make streams run straight. They put levees on top of riverbanks to control flooding. They dammed rivers to create larger sources of drinking water and to provide recreation. Locks and dams were put on major rivers to aid in navigation. These and other changes have had a negative effect on waterway habitats. Channelized streams usually do not have trees and shrubs to shade them. They become warmer and shallower. Soil and chemicals from eroding land move into the water faster and travel farther.
Forests were initially cut by settlers to provide wood for houses, fences and fuel. In the 1850s, timber was needed for railroad ties. It took about six acres of oak woods to provide ties for one mile of railroad. Forests were cleared for roads and towns. As farms became larger in the 1950s, trees along fence rows were cut down. These trees that were cut were hedge rows planted in the 1870s for fences. Osage orange trees were planted for fences before barbed wire was available. If kept trimmed, the "hedge trees" grew very thick. Later, these trees were cut and used for fence posts.
Large animals were the first piece of the prairie community to be affected by settlers. A bounty was placed on wolves nationwide in 1817. Bison and elk were heavily hunted for food and skins. Bison were gone from the state by the 1850s and elk by the 1860s. Around this time the prairie itself was being radically changed. John Deere’s moldboard plow became available to Iowa settlers in the 1850s. With this tool, the settlers had a way to cut through the dense mat of prairie roots. They turned the soil and planted crops. In less than 100 years, over 99 percent of Iowa’s native prairie was gone.
Wetlands were Iowa’s last habitat to be changed. Most people avoided wetland areas because of all the insects. But the federal government gave the land to the counties under the Federal Swamplands Acts of 1850 and 1860. County commissioners were told to drain the land and make it productive. Work to improve navigation on Iowa’s major rivers began in the 1830s. These efforts eventually led to the decline of backwater wetlands. Increased erosion has silted in marshes along lakes. Less than ten percent of Iowa’s wetlands remain.
Iowa’s greatest wealth has been in the products of its habitats. Wood, soil and wildlife are all products that are valuable for business and recreation. For nearly 200 years people have harvested these products. Now, over 90 percent of the land has been changed.
Many people have come to realize
that native habitats are also valuable for business and recreation. Conservationists
are working to identify and protect remaining pieces of natural habitat. Other
groups are trying to recreate native habitat. The Iowa Department of Transportation
sponsors the Living Roadway Trust. This program helps highway departments
grow and maintain prairie plants along roadways. The U.S. Fish and Wildlife
Service operates DeSoto Bend, a backwater of the Missouri River, and the Neal
Smith Prairie Wildlife Refuge. The Neal Smith Refuge is a long-term project to recreate
prairie on over 8,000 acres of land. County Conservation Boards manage wetlands,
forests and prairie communities across the state.
What will Iowa look like after another 200 years? Only time will tell.
- Dinsmore, James J. A Country So Full of Game: The Story of Wildlife in Iowa. University of Iowa Press, Iowa City 1994.
- Iowa Association of Naturalists. Iowa's Biological Communities: Iowa's Biological Community Series. Ames, Iowa: ISU Extension Service, 2001