Environment Lesson 11: Grasslands

Grasslands go by many names. In the U.S. Midwest, they're known as prairies. In South America, they're called pampas. Central Eurasian grasslands are referred to as steppes, while in Africa they're named savannas. What they all have in common is grass as their naturally dominant vegetation. Grasslands are found where there is not enough regular rainfall to support the growth of a forest, but not so little as to form a desert.

In fact, most grasslands are located between forests and deserts. About one quarter of the Earth's land is covered with grasslands, but many of these lands have been turned into farms. Grasslands are generally open and fairly flat, and they exist on every continent except Antarctica. Most lie in the drier portions of a continent's interior.

There are two different kinds of grasslands: tropical and temperate. Grasslands in the southern hemisphere tend to get more precipitation than those in the northern hemisphere. Some grasses grow more than 7 feet (2 meters), and have roots extending several feet into the soil.

Tropical grasslands are warm year round, but usually have a dry and a rainy season. One such tropical grassland, the African savanna, is home to some of the world’s most recognizable species, including elephants, giraffes, rhinos, zebras, lions, hyenas, and warthogs.

Temperate grasslands, which average between 10 and 30 inches (25 and 75 centimeters) of rain per year, have shorter grasses, sometimes just a few millimeters. These areas have two seasons: a growing season and a dormant season. During the dormant season, no grass can grow because it is too cold.

The animals that live in temperate grasslands have adapted to the dry, windy conditions. There are grazing animals like gazelle and deer; burrowing animals such as mice and jack rabbits; and predators such as snakes and coyotes. The North American grasslands were once home to millions of bison, before most of them were slaughtered by humans.

When rainy season arrives, many grasslands become coated with flowers, some of which can survive well into winter with the help of underground storage organs and thick stem bases.

No other habitat is as agriculturally useful to humans as grasslands. Soils tend to be deep and fertile, perfect for cropland or pastures. Much of the North American prairielands have been converted into one of the richest agricultural regions on Earth.

Fires, both natural and human-caused, are important in maintaining grasslands. Ancient hunting peoples set regular fires to maintain and extend grasslands, and prevent fire-intolerant trees and shrubs from taking over. Grasses are able to survive fires because they grow from the bottom instead of the top.

Source: National Geographic