Restoring the Tall-Grass Prairie

Beginning about 150 years ago, most of the prairies and grasslands that once covered the American heartland became fields of wheat, corn, and soybeans.

More recently, suburban neighborhoods and office parks began replacing farms in ever-widening circles around the cities and towns. Conventional practice is to landscape the open spaces around such development with broad expanses of green lawn interspersed with shrubs and trees, a model imported from Europe.

Both the environmental costs and dollar costs of creating and supporting these imported landscapes are very high. The Institute for Real Estate Management puts the dollar cost at $3,500 to $10,000 per acre ($1,400–$4,000 per ha) annually. Now owners of large corporate office parks are beginning to discover that there is a better option. By restoring the land’s original vegetation, they can have strikingly beautiful landscapes, rich in biodiversity, and save huge amounts of money at the same time.

Costs of Traditional Landscaping

Maintenance of traditional landscapes in the Midwest typically includes regular application of herbicides to deter weeds, insecticides to protect the exotic species from attack, fertilizer, and irrigation.

•Herbicides and insecticides contain toxic and hazardous substances that contribute to general environmental degradation. For example, they can kill beneficial predator species, leading to even greater chemical dependence.

•Fertilizers often accumulate in surface waters where they promote algae growth, increase biological oxygen demand (BOD), and otherwise disrupt the balance of aquatic life.

•Irrigation contributes to the depletion of groundwater aquifers, salination of the topsoil, and uses electricity.

•Mowing (of lawns) and trimming (of trees and shrubs) is done with mechanical equipment that requires energy and causes air pollution (two-stroke lawnmowers and chainsaws are particularly polluting). Tractors used on larger lawns also compact the soil.

With or without the additional soil compaction, lawns and hedges are not particularly effective at retaining and absorbing rainwater. Stormwater runoff must be managed, and the usual tools are a substantial infrastructure of retention/detention ponds and ditches or drain tiles (see EBN

Vol. 3, No. 5 for alternative strategies). Even with these measures, excessive stormwater often contributes to downstream flooding, which in the Midwest has been increasing dramatically in recent years.

In addition to harming the environment, all the practices mentioned are expensive (see table). Lawnmowing is required periodically throughout the growing season. Irrigation requires a significant initial investment in infrastructure, as well as regular maintenance of the system. Pesticides and fertilizers are expensive, both to purchase and to apply. The high cost for these landscaping practices creates a tremendous opportunity for savings.

Bringing Back the Natural Ecosystem

Natural alternatives to the typical landscape described above include restoring the native plants of the tall-grass prairie, and using slow-growing and drought-resistant native grasses, such as buffalo grass, for lawns.

The design and implementation of an ecosystem restoration project depend on the specifics of the site and interests of the client. Jim Patchette, president of Conservation Design Forum, Inc. and a leading practitioner of prairie restoration, does not advocate total elimination of traditional landscaping elements. Often, traditional lawns and shrubs are retained in areas adjacent to buildings, transitioning gradually into the native prairie. When possible, stormwater detention systems are converted into ponds and wetlands that effectively remove toxins through biological activity and allow water to infiltrate gradually into the ground.

The prairie is introduced by removing existing sod and shrubs, and planting native species with seeds and, in some cases, plant plugs. Because the perennial plants indigenous to the tall-grass prairie can take several years to become fully established, the area is usually seeded with a temporary crop of annual wildflowers. This temporary matrix creates an attractive field during the transitional period, and helps to suppress unwanted (non-native) plants.

Patchette will in some cases use an herbicide, such as Round Up™, to remove particularly persistent non-native plants from an area to be seeded. The herbicide is never sprayed or broadcast, however; it is applied directly to plants with a wick. Smaller areas may be weeded by hand or mowed.

Advantages of Natural Prairies

The table above illustrated the huge economic advantages of going to natural prairie ecosystems.

Once the initial transition is complete, annual maintenance costs are on the order of one-tenth the cost of maintaining traditional landscapes, saving thousands of dollars per acre.

Having evolved over millennia in the area, native species are adapted to the climatic conditions and can thrive without any of the herbicides, insecticides, fertilizers, mowing, or irrigation that traditional landscaping requires. Prairie plants tend to have extremely large root systems—in some cases as much as 90% of the plant mass is below ground. These help to stabilize the soil, help the plant survive dry periods, and contribute to infiltration of surface water deep into the soil. The root systems are also a long-term carbon sink, taking CO₂ out of the atmosphere and converting it into biomass.

The infiltration of surface water—preventing it from ever becoming stormwater—is extremely important. “Water management is the most critical factor to address,” Patchette says. His experience creating wetlands revealed that surface water running to the wetland was often polluted enough to harm the aquatic system. Water that has leached into a wetland through the soil, however, is much cleaner and healthier. The key to water management is to keep the water where it falls, or treat it on its way into the wetlands system, according to Patchette. “When it gets into the wetland it is already, in a sense, too late,” he says. The ability of native prairie plants to help keep the water where it falls is an important benefit.

One of the most significant casualties of the uniform, traditional lawn is the natural biodiversity of the region. As a small number of imported plant species displace diverse natural systems, many species of fauna and flora are lost. Because of the inter-

connectedness of ecosystems, eliminating one species can have a cascading effect—eliminating other species that depend on the first. When diverse, natural systems are reintroduced an important educational opportunity is provided. People can see the native ecosystems at work and watch them change over the seasons.

The Annual Burn

Once a prairie ecosystem has been reestablished, the only regular maintenance it requires is an annual con-trolled burn. Annual burning was practiced throughout the prairie by the Native Americans who inhabited these areas since the glaciers receded, so the plants evolved under those conditions. Regular burning keeps the plants vibrant and healthy (their robust root systems are unharmed), and prevents the build-up of dry plant material that could contribute to dangerous accidental fires.

Concerns about air pollution from these controlled burns are unfounded, according to Patchette. The prairie is burned at a time in the fall or spring when the plants are very dry, so they burn very quickly and cleanly—unlike the burning of piled leaves that is now banned in many places. Donald Sutton, manager of the permit section of the Illinois Environmental Protection Agency’s Division of Air Pollution Control, confirms that these burns are not a serious problem. “The biggest concern from that type of fire would be particulates,” Sutton reports, but the particulates one gets are much larger than the size that is generally of concern. Sutton also acknowledged, however, that because the burns are a well-established, necessary practice, his agency hasn’t spent much time researching the possible concerns.

An Evolving Practice

The restoration of native prairie ecosystems is a new and evolving practice. There is a great deal to be learned from each site, Patchette reports, and not all the answers are known. While he has some concern about projects being undertaken by contractors without a broad understanding of the ecological issues, Patchette also acknowledges that there are legitimate disagreements among established practitioners of prairie restoration. Given the enormous economic incentives, the practice of restoring natural ecosystems in many bioregions is likely to keep growing. Hopefully the environmental benefits will also continue to generate interest and commitment.

As Paul Hawken states in

The Ecology of Commerce, “We have to recognize that we’ve reached a watershed in the economy, a point at which ‘growth’ and profitability will be increasingly derived from the abatement of environmental degradation, the furthering of ecological restoration, and the mimicking of natural systems of production and consumption.” This understanding may or may not reflect the activities taking place within the buildings of these corporate office parks, but it is certainly the basis for the work of Patchette’s Conservation Design Forum, Inc., and other like-minded companies. Maybe over time the living lessons just outside their windows will rub off on those working inside, and change the nature of their business as well.

– Nadav Malin