Signs of Summer 11: West Toward Home (Part 2)!

Photo by D. Sillman

(Click here to listen to an audio version of this blog!)

We drove out of Indiana and left the ghost of the pre-colonial eastern forest behind. Entering Illinois we crossed the eastern boundary of the now defunct great, tall grass prairie. Another ghost ecosystem! We first negotiated  the road congestion and construction around Chicago (and somehow got that song “Gary Indiana” out of our heads) and then raced across the width of Illinois.

At an Illinois rest stop we once again noted the incredible wind coming from the south. Most of the trees at the stop had branches that were bent and twisted away from the prevailing push of the wind. They must have been sculpted by the incessant blowing. There were a number of chestnut oaks in the “rest stop forest” and a few northern red oaks. They were more widely spaced than the rest stop trees in Indiana. Grassy spaces were taking over from the tree cover.

West of Chicago and its suburbs and exurbs were corn fields and then corn fields and then more corn fields. The complexity of the tall grass prairie (which used to extend across the Mississippi River into Iowa and south across Missouri to Kansas and the northern tip of Oklahoma and north into Minnesota and into the eastern edges of Nebraska and the Dakotas) has been almost completely replaced by a monoculture of a very  useful but very ecologically limited plant.

Why did the eastern forest stop and the prairie grasslands begin here? The average yearly rainfall here in Illinois is very similar to Pennsylvania (Chicago gets 36.9 inches of rain a year while Pittsburgh gets 38.2 inches of rain a year). What was the controlling factor that kept the trees out of these fertile lands? The answer is fire. In the Eastern U.S. the influence of nearby oceans generates a very constant yearly rainfall distribution (this is called a “marine climate”). On average a site in a marine climate each receives about the same amount or precipitation each month of the year. As one moves deeper and deeper into the continent, this monthly rainfall regularity breaks down. There are months, then, of consistently very low rainfall. Typically the winter months (December, January and February) have extremely low precipitation. Des Moines, for example, only gets about one inch of precipitation in each of its winter months compared to four inches of rain in each of its summer months. This type of climate is referred to as a “continental climate.” When these seasonally, continentally dry months connect with adjacent months that can get randomly occurring drought, significant spans of time can be generated in which the surface vegetation becomes tinder dry. It only takes a lightning strike or an intentionally set burn to let loose a wildfire that will scour the land surface of any fire vulnerable plants (like trees and shrubs!).

Tall grass prairie trail. Photo by S. Stone. Wikimedia Commons

The tall grass prairie grass plants are adapted to fire and, in fact, depended on fire for their perpetuation. Indian grass, big and little blue-stem grass and switch grass grew, on average, five to six and half feet tall with some stems rising up to eight or ten feet! The old story my grandmother told me about the grasses obscuring a man on horseback was, amazingly, not a tall tale but the truth!

The grasses were cropped by abundant

Bison herd on tall grass prairie. Photo by NPS. Public Domain.

herbivores (especially the huge herds of bison). The feces of these herbivores then added nitrogen to the soil setting up a sustainable system of growth and renewal. And, periodic fires were the key to maintaining this ecosystem’s structure. Native Americans recognized the utility of fire in these prairie systems. They set fires to drive and concentrate the bison herds and to keep the grasslands vital and productive.

Corn production on the remains of the tall grass prairie is prodigious. The Unite States produces almost twice as much corn as the country ranked second on the world production list (China), and Iowa itself produces more corn than all but five countries in the world! The top four states for corn production (Iowa, Minnesota, Nebraska and Illinois) all lie at least in part within the boundaries of what was the tall grass prairie.

All of this corn is used for a surprising range of products. More than half of the corn grown in the United States goes into ethanol production (37%) and animal feed (33%). Very little (only 11%) is actually used for direct human consumption (mostly in the form of high fructose corn syrup,  beverage alcohols and cereals). The endless fields of corn that we pass on the highway are vast systems mostly for biofuel production. They are living oil derricks, green fuel fields stretching out to the horizons.

One thing, though, that is truly amazing about this incredibly rich and productive farm land is that it was ignored by the first settlers to encounter it! In 1830’s and beyond wagon train after wagon train rolled along on the Oregon Trail right over the top of this land on their way to what they perceived to be more fertile fields of the Northwest. These tall grass prairie plains were part of the “Great American Desert” and were, without any real evaluation, deemed to be unproductive and worthless. Why? Because there were no trees growing here!  Common sense and traditional agricultural theories maintained that trees were the surface icons of fertile soils, and their absence was taken as a critical indication that the soils could not support agriculture. As in many cases, this display of “common sense” was incredibly wrong!

Photo by D. Sillman

We drove across the Mississippi River at Davenport and entered Iowa. For the first 20 miles or so, we drove across rolling countryside but then the flatness of the plains asserted itself. I had a friend who participated in a multi-day bike race in eastern Iowa several years ago. I commented to him that the flatness of the terrain must have been pleasant. He went on and on, though, about the steep hills and deep valleys they had to negotiate. This very “un-Iowan” terrain must be generated by erosion from the surface water drainage into the Mississippi.

We have stayed at a relatively constant altitude all across Ohio, Indiana, Illinois and Iowa. Columbus sits 902 feet above sea level, Indianapolis is at 900 feet and Omaha is at 1089 feet. We will start to rise much more significantly, though, as we go west across Nebraska.

Photo by D. Sillman

The Iowa rest stops were only sparsely wooded. Shade was very hard to find when we stopped to walk the dog or have a quick meal at one of the picnic tables, and the wind continued to blow unceasingly from the south and southwest! All along the western section of Interstate-80 were lines of gigantic wind turbines slowly turning in the power of the steady wind. Iowa is a 21^st Century energy factory! Ethanol corn, electricity from wind. It is the new Saudi Arabia or Texas.

Next: crossing the Missouri River into Nebraska and the edge of the sort grass prairie!