East of Fort Collins, Colorado, USA Photograph by David Olson   Central North America: Central United States Temperate Grasslands, Savannas, and Shrublands   168,000 square miles (435,200 square kilometers) -- slightly larger than California Critical/Endangered

· Lessons from the Dustbowl
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
More Photos

Lessons from the Dustbowl

It was in this ecoregion in the 1930s that prolonged drought and poor land-use practices resulted in the loss of the top layer of soil. Severe dust storms darkened the skies and carried clouds of soil to places as far away as New York City. To prevent a similar disaster from happening again, the United States government formed the Soil Conservation Service, now called the Natural Resources Conservation Service.

Special Features

The western short grasslands are the driest of the North American grasslands. Fire is usually an important force in maintaining grasslands but it damages the shortgrass prarie. In this ecoregion, drought and grazing by herbivores are more important forces than fire.

	An incredible event used to happen in this area -- the annual bison migration. Each year, millions of bison would move north in search of new grass in the spring, and south to milder climates in the fall. Today, the small numbers of bison that survive are generally confined to ranches and no longer migrate long distances.

Wild Side

Growing only to about 1 foot (30 cm) tall, the short grasses of this ecoregion include grama and buffalo grass. They have two different growing strategies. Blue grama grows as a bunchgrass; up to one hundred stems may come out of a single plant! In contrast, buffalo grass sends out shoots that grow two to three inches (5-8 cm) along the ground each day and form dense mats of vegetation called sod. Sod-forming grasses are adapted to grow well under grazing pressures -- historically, they were eaten and stepped upon by enormous herds of bison. But nowadays the main herbivores are cattle. This ecoregion is home to a wide variety of species of butterflies, birds, and mammals. The bird populations declining fastest on the continent live here. They include the lesser prairie chicken, greater prairie chicken, dickcissel, and loggerhead shrike.

Cause for Concern

Cattle grazing has affected 75 percent of this ecoregion, especially in the southern part. This has caused the spread of undesirable, often thorny, shrubs such as mesquite, because cattle do not like to eat these species and that gives them a better chance of survival. This preferential eating and the trampling of native vegetation changes the habitat from a grassland to a desert scrubland. New farming technologies are making it possible to cultivate areas that were infertile or inaccessible in the past, thus extending the loss of native habitats.

For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.