Impacts of Agriculture on Iowa Ecosystems

An essay below from a course I just finished on “Ecology and Systems Thinking” at Maharishi University of Management. Not my best work, and not as thorough as it could be – I think the 1500 word max limit on the assignment kept me from covering all my bases. Anyway… worth sharing:

Abstract

Agriculture has transformed the Iowa landscape almost completely. Three of the most significant impacts of agriculture in Iowa are the devastating and sweeping loss of Iowa’s native tall-grass and wetland prairie ecosystems, degrading soil quality and polluted waterways. Water retention and filtration and soil quality are all directly connected with the services provided by healthy perennial ecosystems. By incentivizing diverse perennial food and fodder crops and the rebuilding and conservation of wetland prairie, modern agriculture can become a more harmonious and sustainable system while still providing for our food needs.

 

Introduction

Agriculture in Iowa is legendary because of its rich productive topsoil matched almost nowhere in the world. The technological evolution of agriculture worldwide has been applied by Iowa farmers in full force, resulting in unprecedented plowing, irrigation, mechanization, and chemical application; these methods have produced more food than ever before at enormous cost to the ecosystems that co-evolved with the landscape over thousands of years. Three of the most significant impacts of agriculture in Iowa are the devastating and sweeping loss of Iowa’s native tall-grass prairie ecosystem, degrading soil quality and polluted waterways.

 

Prairie Ecosystems

The tall-grass prairie once dominated the Iowa landscape; scattered prairie wetlands and forested wetlands bordered rivers and streams, providing habitat for a great variety of species. (IAN101). Animals, reptiles, amphibians and insects created a full and abundant food chain that thrived for centuries, as the tall-grass prairie became one of the most productive ecosystems on the planet. Tens of millions of buffalo and prairie dogs played keystone roles in the prairie ecosystem, providing food and habitat for many other species, and increased water absorption through buffalo wallows and networks of prairie dog towns. (Outwater).

Grasses and forbs created plant communities with up to 250 species that could withstand harsh winds and low temperatures, as well as high heat and periods of drought. The uniquely deep and wide root systems made optimal use of rainfall, raising groundwater levels and keeping soil moist, stable and aerated. (Outwater). “Iowa’s rich soil developed under prairie plants and was held tightly by them. When prairie plants die, their decomposition returns nutrients to the soil, creating a rich, black silty soil.” (Iowa Pathways).

 

It is estimated that less than 1% of the tallgrass prairie survives in its original state” (Outwater). The removal of perennial grasses in the plains goes hand-in hand with Euro-American settlement. Previously, Native Americans lived in symbiosis with the plains, helping to prevent succession of the woodlands by setting fire to the grasslands; these fires were important for maintaining the tall-grass prairie habitat and recycling plant nutrients to the soil.

 

With the movement of white people west in the 1800’s, the homestead act of 1862 was created to provide incentive for people to work the land; people were promised ownership of 160 acres of land after 5 years of work and “improvement” of the land (Outwater). This meant no more prairie burns and no more room for the Natives, who were illegally removed from their lands. (PBS.org). Throughout the late 1800’s railroad companies gained rights to 180million acres, most in the mid-west, and thus the growth of agriculture became a priority for the growing settlements in the west. Without regular burning, the grasslands declined, and along with it went the endless millions of prairie dogs and buffalo, including the rest of the food-web of organisms and species that all play such important roles regulating the transformation of waste, purification of water, and recycling of organic matter that built the soil our farmers benefit from today. (Outwater).

 

Increased mechanization after WWI introduced gas powered tractors and trucks and more effective plowing technology, namely the one-way steel disc plow, which facilitated millions of acres of plowing in the Midwest. Agriculture replaced the perennial prairie-grass ecosystem with annual grasses, mostly corn and spring wheat, which left the ground bare for part of the year. As industrial growth moved west in the 20th century huge grain processing industries and concentrated animal-feed operations developed around the cheap transport and processing of millions of acres planted in a few varieties of annual grasses. The removal of animals from grasslands and the proliferation of vast monoculture farms have definitively changed the landscape of Iowa and the entire mid-west. (Thicke).

 

In our post-modern times, despite knowledge of the important ecological services of the prairie ecosystem, government subsidies tell a tale of “business as usual.” Data compiled by the Environmental Working Group shows Iowa as the 2nd highest recipient of subsidies for agriculture in the nation; of the nearly $23 billion in subsidies given to Iowa farmers between 1995-2010 over $18 billion went to farmers as corn and soybean commodity subsidies as compared to only $3.1 billion for conservation and wetland conservation programs combined. (EWG1). This disparity in funding accounts for the perpetuation of an agricultural system that is largely responsible for the degradation of 2 of our most precious resources: soil and water.

 

Soil Quality

The texture of soil depends on the parent material it came from, vegetation cover, length of time the soil has weathered, the topography of an area, and artificial changes caused by human activities. (Iowa Pathways). Because of the highly productive prairie ecosystem, fertile topsoil in Iowa was considered one of the richest and most abundant in the world. When Iowa land was first plowed, the settlers found 14 to 16 inches of topsoil. By 2000 the average in Iowa was six to eight inches. In the first 100 years of farming, portions of Iowa lost half its topsoil to spring erosion. (Iowa Ag & Environment). Based on the known glacial history and geology of the Iowa landscape the amount of topsoil lost in this short time took approximately 7,000 years to accumulate. (UArk).

 

Soil erosion is the process of removing soil materials from their original sites by water or wind. Hard rains that wash across bare soil move Iowa’s rich growing medium into gullies and streams. During dry weather winds can carry loose soil across the countryside. (omafra.gov). When the prairie plants were plowed under, the soil was to exposed and vulnerable to erosion. The effects of the one-way disk plow contributed to the collapse of soil structure; flocculated soil is stable with heavier microscopic chunks that allow for air, water and roots to go deep and hold soil in place. With plowing, the flocculated soil was pulverized into much smaller lighter particles. Further, the loss of soil-stabilization by the perennial presence of deep prairie grass roots left the ground bare for part of the year, and without plant cover runoff increases. “Muddy torrents gully the ground, and the Mississippi becomes laden with silt as topsoil goes into the sea.” (Outwater).

 

The high-intensity annual Iowa agricultural system, subsidized and supported by federal funds, has set the conditions for continued soil erosion and decreasing soil fertility. It is common knowledge that annual plowing compacts the soil underneath the reach of the plow in the soil, creating a “till-pan” that prevents water and air passages and serves as a runway for water down contour; further, field tiles drain water from low lands directly into gullies and streams. There is simply not enough plant cover with root systems to absorb the muddy water as it carries polluted soil into waterways, compromising the habitats of aquatic life. In order to stop erosion, our agriculture must include more perennial food crops and more economic incentive to remove field tiles and rebuild tall-grass and wetland prairies near waterways.

 

Water Quality

With the removal of the prairie and its natural water filtering capacity, and the increase of toxic fertilizer accompanying silt runoff into waterways, Iowa agriculture has created a water problem. Overall nitrogen fertilizer use is concentrated in the Corn Belt, of which Iowa is a member. (EWG2). Data from the Environmental Working Group shows that “increases in nitrate contamination in Iowa groundwater correspond closely to increases in nitrogen fertilizer use,” and concludes: “Agriculture is the chief cause of widespread groundwater and surface water contamination with nitrate in the United States.” (EWG3, EWG4)

 

Nitrogen stimulates the growth of algae, which depletes oxygen levels in water, creating an uninhabitable environment for most aquatic life. We now know that changes in down-stream water chemistry and habitat are linked with “dead-zone” effects in Gulf of Mexico. This is caused by leakage of nitrogen fertilizer through field tile drains into the waterways. (Thicke). The effect of nitrogen fertilizer is just one example of the problems associated with dependence on chemical applications in our modern production system, and highlights the need for a more biological approach.

 

 

Interconnections

The prairie ecosystem once provided food, shelter, and water for a complex diversity of species; the soil-building and water-holding and filtering capacity of the perennial grasses over a long period of time is directly connected with the fertility of Iowa’s current agricultural lands and deep water tables and aquifers. The decline of soil fertility and increased rate of soil erosion is a product of the removal of prairie root systems and the tillage that comes along with annual row crops. Fertilizers and pesticides pollute water that is engineered by farmers to leave the land quickly for the sake of agriculture. Overall, the soil and water problems of today are the result of the perennial systems that were lost together with today’s plowed lands drained and tiled for a few species of annual crops treated with chemicals each year. The systems diagram adds evidence to the case for changing agricultural practices to rebuild and conserve wetland prairie, use fewer chemicals, and more perennial food and fodder crops in field rotations with integrated livestock grazing.

 

Conclusion

As the industrial revolution provided machinery and techniques for plowing and cultivating vast acres of land, agriculture thrived and natural ecosystems declined. Today in Iowa, the landscape has been completely transformed from tall-grass prairie and woodland to large patches of fields growing single species over hundreds and thousands of acres. Modern farming practices and the subsidies that support its growth are largely responsible for unsustainable soil erosion rates and pollution of waterways, which is exacerbated by a lack of biological filtration and soil stabilization once provided by the native prairies. Perennial plant growth, water and soil quality are interconnected, and it is clear that our methods of agriculture must change to support biodiversity in the soil, in the plants that we grow, and in providing more land for wildlife conservation and prairie reconstruction.  Increasing conservation subsidies and increasing acreage in perennial food and fodder crops will go a long way to remedying the environmental damage.

 

Sources:

Iowa Pathways:

EWG1:

EWG2:

EWG3:

EWG4:

 

Iowa Agricultural Practices and the Environment, Iowa Association of Naturalists: Iowa Environmental Issues Series

Iowa Habitat Loss and Disappearance, Iowa Association of Naturalists: Iowa Environmental Series

 

omafra.gov

 

Outwater, Alice. “Water: A Natural History”

 

PBS.org:

 

Thicke, Francis. “A New Vision for Iowa Food and Agriculture”

 

UArk:

 

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One response to “Impacts of Agriculture on Iowa Ecosystems

  1. Pingback: Prairie Song Burns | Creative Intelligence

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