Free State Prairie
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Lawrence Free State High School
The Effect of Climate on Prairies
Climate is the longterm average of weather in a particular area and climate types are typically classified based on measurements of temperature and precipitation. In Kansas, the average temperature ranges from 50-degrees in the extreme northwest corner of the state to 58 degrees in the southeast corner. Average annual precipitation in varies from 15-20 inches in far western Kansas to 40-45 inches at the Kansas-Missouri border. The diagram at right is called a climatogram and shows monthly averages of both temperature and precipitation for Lawrence, Kansas. Click on the diagram for more detailed information.
What is climate?
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How does climate affect prairie ecosystems?
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Prairies are a type of temperate grassland biome located on the North America continent. There are temperate grasslands on every continent (savannah, pampas, steppe, etc.) except Antarctica and all are located in the interior of the continent, not near a coast. The climate of these grasslands is determined by the geophysical properties of latitude, terrain, altitude, and nearby bodies of water and their currents. The amount of moisture and range of temperature (climate) of an ecosystem largely determines the organisms that can best survive there. For example, the amount of annual rainfall across Kansas varies from less than 20" in the west to more than 42" on the eastern side of the state. Consequently, short-grass prairie ecosystem dominates western Kansas while tall-grass prairie is dominant in eastern Kansas.
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What determines the climate of the great Plains?
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The vast expanse of the Great Plains originated around 80-55 million years ago with the uplift of the Rocky Mountains by tectonic forces under the North American plate. The mountains create a rainshadow effect that blocks the eastward movement of winds carrying moisture from the Pacific ocean. Moist air traveling eastward from the Pacific ocean must rise up to high altitudes to travel over the Rockies. As air rises, it expands and cools. Because cooler air cannot hold as much moisture as warmer air, the moisture falls as precipitation on the western side of the Rocky Mountains.
The air flowing over and down the eastern side of the mountains is much drier and only later picks up additional moisture from the Gulf of Mexico as it travels across eastern Kansas. This rain shadow effect creates a drier climate in the western plains that limits the growth of trees and taller vegetation to the riparian zone along banks of streams. In the eastern plains there is more annual precipitation, so plants are able to grow taller and trees are more common, though historically largely restricted to areas adjacent to streams.
How will climate change affect our kansas prairies?
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Climate Change is impacting ecosystems around the world in different ways. According to the National Oceanic and Atmospheric Administration, the past decade has been the hottest on record for Kansas aside from a slightly hotter peiod in the 1930s when poor land management practices likely combined with drought to cause high temperatures during the Dust Bowl. The average temperature in Kansas has risen 2 degrees since the beginning of this century. The number of very cold nights has decreased since 1990 and the freeze free season has increased an average of 9 days since 2000. Our industrial agriculture economy depends on large areas of periodically bare soil may contribute to more serious effects of drought and heat. The number and intensity of wildfires is projected to increase while the amount of wetlands will likely decrease. Even slight changes in temperature can significantly change the numbers and types of organisms that make up an ecosystem.
