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You’ve probably heard of the Great Plains, prairies, and Loess Hills, but how are they defined and what makes them different? The U.S. Environmental Protection Agency (EPA), in conjunction with the Commission for Environmental Cooperation, organizes North America into multiple levels of ecoregions, from the broad, continental scale (such as the Great Plains) to a much more localized, county-level scale like the Loess Hills. “A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I is the coarsest level, dividing North America into 15 broad ecological regions. These highlight major ecological areas and provide the broad backdrop to the ecological mosaic of the continent, putting it in context at global or intercontinental scales.” (Source: Commission for Environmental Cooperation). Click the image below to open a larger pdf map.  All of western Iowa is included in Region 9: the Great Plains, although other definitions of the Great Plains do not include Iowa. The Great Plains covers a large portion of the central part of North American, from Canada through Mexico. According to CEC: “This ecological region is distinguished particularly by the following characteristics: relatively little topographic relief; grasslands and a paucity of forests; and subhumid to semiarid climate… The soils are commonly deep and throughout most of the region were originally highly fertile…The climate is dry and continental, characterized in the north by short, hot summers and long, cold winters. High winds are an important climatic factor in this ecological region. It is also subject to periodic, intense droughts and frosts… Rainfall increases from west to east, defining different types of native prairies. Short-grass prairie occurs in the west, in the rain shadow of the Rocky Mountains, with mixed-grass prairie in the central Great Plains and tall-grass prairie in the wetter eastern region… Because of the suitability of the Great Plains for agricultural production, many native prairie vegetation types have been radically transformed. The short-, mixed- and tall-grass prairies now correspond to the western rangelands, the wheat belt and the corn/soybean regions, respectively, to the central and eastern Great Plains.” Within Region 1 Ecoregions are 50 Level II ecological regions “delineated to provide a more detailed description of the large ecological areas nested within the level I regions. Level II ecological regions are useful for national and subcontinental overviews of ecological patterns.” (Source: CEC). ' All of Western Iowa is included in 9.2: Temperate Prairies.  According to bplant.org: “The Temperate Prairies are a Level II ecoregion representing the northeasternmost portion of the Great Plains. Entering them from the east, they represent the first region in which forests are not the dominant cover, and instead grasslands dominate. This region stretches over a long, but somewhat narrow expanse from Alberta, Saskatchewan and Manitoba in Canada, south through the eastern Dakotas and western/southern Minnesota, and south to northeastern Oklahoma. Iowa is the only state mostly contained within this region, which cuts through narrow bands of many states and provinces. This region is mostly flat, although it does have gently-rolling hills. The climate is continental, and moisture levels range from subhumid to semiarid in the north, to humid in the south. To the south, higher evapotranspiration associated with warmer temperatures and greater sunlight demand more water to sustain similar vegetation cover. The weather is unpredictable and can be extreme, with large temperature swings being common at all times of year, as well as prolonged periods of drought. The natural cover in this region is mostly grasslands, with only scattered trees, mostly along streams and other bodies of water. However, this region has been heavily utilized for agriculture, and cropland is now the dominant cover, with significant pastureland as well. This region is not as heavily populated as areas to the east, but it does contain major metro areas including Kansas City, part of the Twin Cities metro area, and Calgary and Edmonton, AB.” Within the 50 Level II ecoregions are another 182 Level III ecoregions. “The level III ecological region map depicts revisions and subdivisions of earlier level I, II, and III ecological regions (CEC 1997, McMahon et al., 2001, Omernik 1987, USEPA 2006; Wiken 1986, Wiken et al., 1996). These smaller divisions enhance regional environmental monitoring, assessment and reporting, as well as decision-making. Because level III regions are smaller, they allow locally defining characteristics to be identified, and more specifically oriented management strategies to be formulated.” (Source: CEC) click the map for a larger pdf  Nearly all of Iowa, excepting the northeast and southeast corners, is included within Level III Ecoregion 9.2.3: the Western Corn Belt Plains. Per EPA, “Once covered with tallgrass prairie, over 75 percent of the Western Corn Belt Plains is now used for cropland agriculture and much of the remainder is in forage for livestock. A combination of nearly level to gently rolling glaciated till plains and hilly loess plains, an average annual precipitation of 63-89 cm, which occurs mainly in the growing season, and fertile, warm, moist soils make this on of the most productive areas of corn and soybeans in the world. Major environmental concerns in the region include surface and groundwater contamination from fertilizer and pesticide applications as well as impacts from concentrated livestock production.” Within Level III are the most localized landforms, Level IV. This is where the Loess Hills are delineated. Also called the “Western Loess Hills”, and identified as 47m on the Level IV map: click the map for a larger pdf.  According to the EPA: “The Western Loess Hills ecoregion extends south from Iowa and covers only a small area in northwestern Missouri. The deep loess-dominated hills have greater relief and a higher drainage density than the Steeply Rolling Loess Prairies (47e) to the east. The more irregular topography and erosive, silty soils contribute to a mixed land use with less cropland and more pasture and woodland than neighboring regions. The flora of this region is mixed, with shortgrass and mixed-grass prairie and rare xeric species on south and west-facing slopes, and bur-oak woodland and tallgrass prairie on cooler, moister slopes.” Other Level IV ecoregions in western Iowa include 47e -- Steeply Rolling Loess Prairies immediately east of the Loess Hills, and 47d -- Missouri Alluvial Plain along the Missouri River to the west of the Loess Hills.  Each ecoregion has distinct geological features and characteristics, which often result in different land-use, economic, and even social & cultural impacts.The Loess Hills and Missouri Alluvial Plain, for example, are very different and easy to distinguish from one another visually–steep bluffs overlooking a wide, flat river valley and floodplain. Their native floral communities are different, and modern farming practices vary between the hills and the plain. Between the Western Loess Hills and Steeply Rolling Loess Prairies, however, the difference is much more subtle, as the depth of loess slowly decreases from west to east. The rolling hills covered in loess continue eastward across much of Iowa, with less and less loess as you move east. Take a look at the landscape as your travel across western Iowa and see if you can tell when you cross into a new ecoregion!
View the map and read descriptions for other Level IV ecoregions here.
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