Northeast of Navasota in Grimes County, Texas, USA Photograph by Jim Manhart   Southern North America: Southern United States Temperate Grasslands, Savannas, and Shrublands   19,400 square miles (50,300 square kilometers) -- about twice the size of Maryland Critical/Endangered

· What’s a Mima Mound?
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
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What’s a Mima Mound?

Mima mounds are piles of soil up to 46 feet (14 m) across at the base and more than 3.3 feet (1 m) high. How they originated is not clear. These mounds are found in the eastern portion of this region. Distinct zones of plants and different habitats can be found on a single undisturbed mound when vernal pools form between the mounds, and then dry out, creating microhabitats.

Special Features

Three types of soil can be found in this ecoregion. Vertisols are clays that swell and shrink depending upon weather conditions and available moisture, mollisols are rich and fertile, and alfisols are clays that usually form under deciduous forests, which are found in this ecoregion along rivers and creeks.

	The pocket gopher is uniquely adapted to spend most of its life underground. It has tiny eyes (no need for good vision underground), long, sharp claws for digging, and lips that close behind its front teeth. These lips keep dirt out of the gopher's mouth as the animal excavates new tunnels.

Wild Side

The Texas Blackland Prairies ecoregion is home to more than 500 species of animals, from pocket gophers to reptiles and birds. The area's high biodiversity is linked to its variety of soils. In the higher regions of this ecoregion you will find many tallgrass prairie plants. Grasses of the region include big and little bluestem, Indian grass, gamagrass, and switchgrass. Other plants, such as silveanus dropseed, mead's sedge, and brownseed paspalum, also live here.

Cause for Concern

At one time, naturally caused fires eliminated tree and shrub seedlings and thus allowed only grasses to grow in this ecoregion. But fire supression has led to the spread of woody shrubs, many of which are exotic species. Bison, which also helped maintain the grasses of this area, were gone from the region by the 1850s. The problem now is that the pieces of intact habitat are not sufficiently large to bring the bison or controlled fires back to the area. By as early as the 1920s, more than 80 percent of the ecoregion's original vegetation cover had been lost to farming, but today urbanization is also another big threat. Fewer than 1 percent of the original plant species of the ecoregion remain, and only in scattered areas.

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