How do humans change their environment?

The current Iowa landscape owes much to the most recent Ice Age and the glaciers that edged down from the north. As the climate grew colder, ice and snow did not melt off over southern Canada but piled up and pushed out the outer edges of huge ice sheets in the form of glaciers. One account describes it as similar to a pancake on the griddle spreading out as batter pours into the center. Several glaciers covered all or portions of Iowa. Northeastern Iowa is called the driftless area because it received little or no glaciation.

From "Great Desert" to Fertile Oasis

At the end of the most recent ice age, the climate was unsteady with periods of warming and cooling. When the unstable climate turned cold and then warmed, glaciers scraped across north central Iowa and then retreated, back and forth, creating flat surfaces and pulverizing rocks and gravel into fine particles. When the climate finally began warming up and drying out, evergreen forests appeared first, then hardwoods, and finally the grasslands the came to characterize the region as we know it. Season after season, the grasses and other prairie plants grew and died, leaving their roots in the soil to create the incredible topsoil for which Iowa is famous. The glaciers left western and southern portions of the state more hilly.

When American explorers began to investigate the newly-purchased Louisiana Territory, Iowa was considered a "great desert." The fertility of the land was measured by its ability to grow trees, and the prairies looked like miles and miles of barren acres. It was not until early families began moving out onto the prairies and, with John Deere's steel plow, scoured off the sticky prairie dirt, discovering the incredible fertility of the deep, black topsoil.

At the beginning of European settlement, Iowa was around 85 percent prairies, treeless grasslands. Trees grew in the hills of southeast Iowa and along major rivers, but on the uplands back from the waterways, fires burned off trees and other woody plants. Early settlers tried to include at least some timber land in their purchases for the fuel, fencing and lumber they needed. Lumber mills along the Mississippi and inland rivers created Iowa’s first millionaires as the flood of settlers that the railroads brought with them built homes, barns and outbuildings and businesses. The coming of the railroads took more trees to make railroad ties. Today, less than 0.1 percent of Iowa's original prairies are left; the rest of the land has been plowed or in some other way altered.

Different Uses for Iowa's Land

Not all Iowa farmland is used in the same way. In the hills of northeast Iowa, dairy farming has deep roots as farmers harvest hay through the summer to feed their herds through the winter. The hillsides are too steep to plow but abundant rainfall produces excellent pasture. Hilly land in southern and western Iowa support livestock production. Many farmers raise herds that produce calves in the spring that graze to a certain weight and then are shipped north to feedlots where they are finished on corn. The flat, fertile fields of north central Iowa are some of the world's most valuable farming acres. Corn and soybeans dominate the landscape, often to the exclusion of trees, shrubs and wildlife habitat that once supported a variety of birds and wildlife. With larger and larger equipment, a single farm operation can now manage thousands of acres, reducing the number of farms, farm families and the small towns that once supported them.

Farming practices have greatly affected the land. In early Iowa, swamps and wetlands accumulated water in rainy seasons making farming impossible. Tiling ponds to drain the water from ponds and wet lands opened thousands of acres to the plow but created the potential for flooding as excess water flowed into streams and rivers very quickly. The use of commercial fertilizers created ecological challenges in the lower Mississippi as chemicals that kill of vegetation and fish accumulate. Deep plowing and rapid run-off also encourages erosion and the loss of Iowa's most precious resource, its rich topsoil. Livestock confinement operations can concentrate animal wastes that can pollute steams or the air. Efforts are now being explored that try to minimize the impacts of these challenges while still allowing the farm production vital to the state’s economy and the world's food and fuel supplies.

Supporting Questions

How has land been changed to grow food? 

• "Millions of Acres" Advertisement, 1872 (Image)
• Letter from Giles S. Thomas to His Family, January 3, 1876 (Document)
• "A Modern Iowa Farm," 1927 (Image)
• Farmer Plowing Sod in Grundy County, Iowa, 1940 (Image)
• Plowed Sod in Grundy County, Iowa, 1940 (Image)

How has land been changed to provide energy?

• View of Top of Nevada Power Plant at Hoover Dam, Date Unknown (Image)
• "British Reported Set To Build World's First Nuclear Power Station" Newspaper Article, August 8, 1951 (Document)
• Farm in Hardin County, Iowa, August 18, 2008 (Image)
• View of Eagle Butte Coal Mine in Gillette, Wyoming, August 20, 2008 (Image)
• Nuclear Power Plant in Northern California, 2012 (Image)

How has the environment been impacted by human land use?

• "Preserve Your Forests from Destruction" Illustration, January 9, 1884 (Image)
• "Farm Wells and Pollution" Newspaper Article, February 25, 1916 (Document)
• "Deforestation Means Famine in U.S." Newspaper Article, May 23, 1921 (Document)
• Dubuque "Shacktown" Near the Banks of a Polluted Stream, April 1940 (Image)
• "Results of Deforestation" in San Juan County, Colorado, September 1940 (Image)