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Land Formation in Iowa


Iowa was covered by glaciers until 15,000 years ago. These massive flowing sheets of ice would creep along like very slowly moving rivers, picking up lots of different minerals, rocks, soil and debris along the way. As the glaciers melted, rocks and minerals got left behind. We call this glacial till. The water, from the ice melt, is the foundation of our many river valleys as well as some of our lakes and wetlands. These rocks and minerals were slowly broken down by water and microorganisms to form new soil. Iowa’s landscape gradually became covered in a vast Prairie, consisting of hundreds of species of grasses, flowers, birds, mammals, insects and soil organisms. For thousands of years the cycle of prairie plants growing, dying and decaying formed a thick layer of rich top soil. Iowa was one of the most biologically diverse ecosystems in the world. Also dotting the Prairie were numerous wetlands or Prairie potholes. Prairies and wetlands work together to build rich, healthy soils, keep Iowa’s water clean and feed its inhabitants. In the 1800’s European settlers moved into Iowa. In order to feed their families, small sections of the Prairie were slowly broken or turned over for planting crops and gardens while livestock grazed the Prairie. Wetlands were drained so the fertile land could be farmed. With the invention of the steel moldboard plow in 1837, Iowa’s landscape was rapidly transformed from one of the most diverse ecosystems in the world, to one of the most altered landscapes. Today less than 1% of Iowa’s native prairies and ten percent of its wetlands remain. For generations, farmers have turned over the rich black soil, plowing under corn stalks and plant residue after harvest. Without plant material to protect the land surface, this rich topsoil can easily blow away or get washed away into streams, rivers or lakes. What takes the Earth500-1000 years to make, can be lost in 10 to 15 years. Farming right up to the edge of streams and rivers can leave the land vulnerable to streambank erosion. So what can be done? Increasing no-till and strip till farming, leaves the majority of plant residue on the land, to protect the soil from erosion, so it doesn’t pollute our water. Prairie and wetlands were part of our past and our key to our future. We can plant small strips of prairie where they can best capture nutrients and soil before they reach streams. Prairie strips can reduce erosion by 90%. Re-establishing wetlands will help clean our water by removing sediment, nutrients and chemicals. Wetlands have many important jobs to do. Beyond their beauty, prairies and wetlands provide habitat for mammals, birds, insects and many other types of wildlife. If we are to leave the land in better shape for future generations prairies, wetlands and croplands must work together to nurture a diverse landscape, fertile soils and clean waters.

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