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A shelterbelt is an area planted with trees and shrubs arranged in rows to form a barrier to reduce surface winds. Planted throughout the Great Plains, shelterbelts provide wind protection for homes, farms and ranches, highways, livestock, crops, and a diversity of habitats for numerous species of wildlife. This biodiversity helps maintain various predatorprey relationships and contributes to biological control of crop pests.
Shelterbelts were first planted in the region by early settlers. Many brought tree seeds and seedlings from the East or gathered seedlings from local native stands and planted them around their homes for protection, firewood, and beauty. During the agricultural expansion of the early 1900s, much of the native grassland was plowed and planted to wheat. As the drought conditions of the 1920s intensified, many agricultural fields in the region were abandoned, and wind erosion escalated.
In 1935, the U.S. Forest Service undertook
the largest tree-planting effort ever conducted,
the Prairie States Forestry Project. During the
next eight years, with labor provided by the
Works Project Administration (WPA), more
than 222 million tree seedlings were planted,
creating in excess of 18,500 miles of shelterbelts.
Most of these shelterbelts were ten to
sixteen rows wide and a mile long. Even under
the dry conditions of the time, most seedlings
survived and for the next thirty to forty years
provided protection to the agricultural lands
of the region.
While many of these original shelterbelts still exist around farmsteads, most of the wide-row field shelterbelts have been removed to make way for center-pivot irrigation systems or field consolidation. Some have been replaced with single or double-row field windbreaks. Today, the Natural Resource Conservation Service has primary responsibility for shelterbelts and soil conservation efforts. In cooperation with state forestry agencies and local conservation districts, more than 20 million tree and shrub seedlings are planted annually throughout the Great Plains, many in shelterbelts.
Similar efforts occurred in the Prairie Provinces under the direction of the Prairie Farm Rehabilitation Administration. Since the beginning of tree planting efforts in 1892, more than 500 million seedlings have been distributed to landowners, and today four to six million seedlings are distributed to landowners each year.
Shelterbelts work by reducing wind speed on the leeward side of the shelterbelt. The amount of wind speed reduction is determined by the number and arrangement of trees and shrubs in the shelterbelt: the denser the shelterbelt, the greater the reduction. The size of the protected area depends on the length and height of the shelterbelt. For example, a twenty-five-foot tall, moderately dense shelterbelt will reduce wind speed for a distance of 250 to 500 feet leeward. In this sheltered zone, temperature and humidity are increased slightly and evaporation is reduced. The goal of any shelterbelt planting is to use the microclimate created in the sheltered area to the advantage of the landowner. In winter the reduced wind speed means a significant reduction in wind chill temperatures and a 20 to 40 percent reduction in the amount of energy needed to heat a home. Outdoor activities are more pleasant in farmyards or livestock areas when wind protection is available. Livestock that are protected require less feed and suffer fewer heath problems. Field shelterbelts help control wind erosion and increase production of crops on sheltered fields by an average of 12 to 15 percent, providing producers with increased economic returns. Living snow fences of trees and shrubs planted along highways reduce snow removal costs and decrease traffic accidents.