Ecoregions of Iowa and Missouri.

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources; they are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. Ecoregions are directly applicable to the immediate needs of state agencies, including the development of biological criteria and water quality standards, and the establishment of management goals for nonpoint-source pollution. They are also relevant to integrated ecosystem management, an ultimate goal of most federal and state resource management agencies.

The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of the patterns of biotic and abiotic phenomena that reflect differences in ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I and level II divide the North American continent into 15 and 52 regions, respectively (Commission for Environmental Cooperation Working Group 1997). At level III, the continental United States contains 104 regions (United States Environmental Protection Agency [US EPA], 2000). However, depending on the objectives of a particular project, ecoregions may be aggregated within levels of the hierarchy for data analysis and interpretation. Explanations of the methods used to define the US EPA’s ecoregions are given in Omernik (1995), Griffith and others (1994), and Gallant and others (1989).

Level III Ecoregions of the Conterminous United States. (Map source: USEPA, 2000)

This level III and IV ecoregion map was compiled at a 1:250,000-scale; it depicts revisions and subdivisions of earlier level III ecoregions that were originally compiled at a smaller scale (US EPA, 2000; Omernik, 1987). This poster is the product of a collaborative effort primarily between the US EPA Region VII, the US EPA National Health and Environmental Effects Research Laboratory (Corvallis, Oregon), the Missouri Department of Environmental Quality (NDEQ), the Missouri Game and Parks Commission (NGPC), the Iowa Biological Survey (KBS), the Iowa Geological Survey (KGS), the Iowa Department of Health and Environment, Division of Environment (KDHE), Iowa Department of Wildlife and Parks (KDWP), the United States Department of Agriculture - Natural Resources Conservation Service (NRCS) (formerly the Soil Conservation Service), and the United States Department of the Interior - U.S. Geological Survey (USGS) - Earth Resources Observation Systems (EROS) Data Center.

This project is associated with an interagency effort to develop a common framework of ecological regions. Reaching that objective requires recognition of the differences in the conceptual approaches and mapping methodologies that have been used to develop the most commonly used existing ecoregion-type frameworks, including those developed by the USFS (United States Forest Service) (Bailey and others, 1994), the US EPA (Omernik, 1987, 1995), and the NRCS (United States Department of Agriculture - Soil Conservation Service, 1981). As each of these frameworks is further developed, the differences between them lessen. Regional collaborative projects such as this one in Missouri and Iowa, where agreement can be reached among multiple resource management agencies, is a step in the direction of attaining commonality and consistency in ecoregion frameworks for the entire nation.

39. Ozark Highlands The Ozark Highlands ecoregion has a more irregular physiography and is generally more forested than adjacent regions, with the exception of the Boston Mountains (38) to the south. Soils are mostly derived from cherty carbonate rocks, with chert stone comprising about 20% to 60% of the soil mass. Cambrian and Ordovician dolomite and sandstone comprise the dominant bedrock in the interior of the region with Mississippian limestone underlying the western outer regions. Shale, chert, and Precambrian igneous rocks are also present. Topography varies from steep slopes near the large streams to moderate relief hills on the broad plateaus or inter-stream areas. Karst features, including caves, springs, and spring-fed streams are found throughout most of the region. High-gradient, clear-flowing streams in entrenched valley meanders are also common. More than 60% of the total area is open forest or woodland, although in the more rugged sections the forest covers nearly all of the upland. Oak is the predominant forest type, but mixed stands of oak and pine are also common, with pine concentrations greatest to the southeast. Cultivated land is mainly confined to small tracts in the numerous valleys and small creek bottoms. Cleared upland is used for pasture and livestock.
39a. The Springfield Plateau ecoregion is a smooth to gently rolling plain underlain by Mississippian-age cherty limestone and is less dissected than most regions in the Ozarks. A moderate topography and a potential natural vegetation of tallgrass prairie, deciduous forest, and savanna characterize this transitional area where the prairies of the Cherokee Plains (40d) grade into the woodlands of the Ozarks. However, unlike the neighboring plains, this region has karst features and rocky soils, especially in wooded areas. Land cover is a mix of woodland and areas of pastureland in the cleared prairies. Lead and zinc were mined in the southwest portion of this region and mining tailings still remain. 39b. The Elk River Hills ecoregion includes areas of rolling plains and more rugged hills with steep slopes and narrow ridges than the neighboring Springfield Plateau (39a). Soils are rocky and thin over carbonate bedrock and support potential natural vegetation of oak woodland, savanna and some limited glade areas, with prairie comprising only about 7% of the area. This marks a transition from the greater prairie component of the Springfield Plateau (39a), to the mixed oak woodland, scattered pine-oak and glades of the White River Hills (39c) to the east. This region currently has substantial areas in poultry production, especially across the Missouri border into Arkansas, which have impacted water quality. 39c. The White River Hills ecoregion is one of the more dissected areas in the Ozark region with local relief of 200 to 600 feet. Dissected Ordovician dolomite and some sandstone, with step-like topography of level-crested buttes, lower benches, and bottomlands are common. Potential natural vegetation is a mosaic of oak and oak-pine forest and woodland, interspersed with widespread limestone or dolomite glades. Cliffs, sinkholes, and caves are prevalent, with some of the largest caves in Missouri found in this region. Large springs, high-gradient, sustained-flow streams, as well as many smaller losing streams that are often dry are typical. There are significant water impoundments in this ecoregion with the entire length of the White River in Missouri impounded into three reservoirs (Table Rock Lake, Bull Shoals Lake, and Lake Taneycomo). The dissected topography and the thin, rocky soils provide little arable land. Consequently, land cover is principally woodland and much of the area is in public lands. 39d. Surrounded by hill regions, except for the Springfield Plateau (39a) to the west, the Central Plateau ecoregion is less dissected than most regions in the interior Ozark Highlands. Streams flowing across the region have divided it into a large number of small plateaus. Pennsylvanian strata underlie low relief areas in the north. Most of the surface, however, is underlain by Ordovician carbonates. Bedrock is mantled by a thick solution residuum and loess, and karst features are extensive with large sinkhole areas. The potential natural vegetation of this region is tallgrass prairie, savanna, and post-oak woodlands, with a larger area of prairie vegetation than neighboring regions. The majority of the land is cleared and used for pasture; farms are found mainly on the uplands. Cherty soils predominate, although they are not as cherty as in surrounding hill regions. Large areas of clay and sandy soils also occur and areas with Pennsylvanian clay-filled sinks are mined for fire clay. The region has less surface water and soils are generally more droughty than in surrounding regions. 39e. The Osage/Gasconade Hills ecoregion is more densely forested and dissected than the lower relief Central Plateau (39d) to the south. Steep slopes and narrow ridges of carbonate and sandstone underlie soils which are rocky and thin. Outcrops of Gasconade dolomite with some sandstone are found throughout the region along with areas of Roubidoux sandstone, Jefferson City-Cotter dolomites and scattered Mississippian limestone outliers in the western portion. Numerous caves, springs, calcareous wet meadows, losing streams, and streams with entrenched valley meanders are common. Streams flow generally northward and drain into the Missouri River. The potential natural vegetation is predominantly mixed oak forest, with oak-pine forest and some pine forests in the southeast areas of the region and some small limestone and sandstone glades. The northeastern edges of this region are transitional and blend into the Interior River Valleys and Hills (72) ecoregion. 39f. The St. Francois Knobs and Basins ecoregion contains the oldest geologic formations in the state and has a different landscape than surrounding regions. The igneous bedrock knobs of Precambrian granite, rhyolite, and intermediate rocks rise 200 to 900 feet above the intervening basins which are underlain by Cambrian sedimentary rocks, primarily carbonate with some sandstone. This is the only region within the Ozark Highlands (39) that generally lacks karst topography. Streams are smaller than in neighboring regions but have a greater fall distance because of the steep topography. Sedimentary-derived soils may be stone free, not cherty as in neighboring regions. The soil mantle is generally shallow with low fertility, except in the basins, which have a thicker, more loamy layer. The potential natural vegetation includes scrub-oak, post-oak, and blackjack oak forests and glade areas, along with prairie in the basins and valleys. Most of the region is in forest and woodland, with cleared land limited to the small basin-like valleys used for pasture and limited cropland. Lead mining has been an important activity in this region for over two centuries and significant scarification has occurred. Other mineral resources include granite and, to a limited extent, silver, copper, and cobalt, by-products of lead mining. 39g. The Meramec River Hills ecoregion is deeply dissected, with steep-sided hills and chert-covered ridges. The hills tend to be more rugged than in the Osage/Gasconade Hills (39e) ecoregion to the northwest. Land use is mainly timber and recreation, with some pastureland for grazing, and barite and iron mining in the southeast. The potential natural vegetation in this region is shortleaf pine-oak forest and woodland, with a greater oak concentration than in forests of the Current River Hills (39h) to the south. Streams in this region drain northeast into the Mississippi River. 39h. In many ways, the physiography of the Current River Hills ecoregion is similar to that of the Meramec River Hills (39g) to the north. However, this region has many endemic species not found in other Ozark regions and the potential natural vegetation here has a greater pine concentration than in regions to the north and west. The region underwent intensive timber cutting in the early decades of the twentieth century. It now sustains major recreational activities. The stream valleys contain numerous, large, high-quality springs and water quality is generally better than elsewhere in Missouri. Caves and losing streams are common. Streams drain southeast into the Mississippi River. 39i. The Eastern Ozark Border ecoregion is a transitional area between the interior ecoregions of the Ozark Highlands (39) and the Interior River Valleys and Hills (72) ecoregion to the east. Moderately dissected hills and sheer bluffs typify the region. Soils can be rocky and thin on steep slopes, with areas of claypan or loess similar to the Black River Hills Border (39j) to the southwest. Compared to the Central Plateau (39d), however, the loess mantle in this region tends to be deeper and more expansive on the uplands. Potential natural vegetation is a mix of oak forest, savanna, glades, and prairies. Land cover is variable with forests, woodlands, and cleared areas in cropland and pasture. This ecoregion has more cropland agriculture than adjoining Ozark regions (39j, 39f). 39j. The Black River Hills Border is a transitional region with broad, flat inter-stream divides and moderately dissected hills. There is significantly less relief than in neighboring hill regions in the Ozark Highlands (39) but greater relief than in the southeastern Mississippi Alluvial Plain (73). Soils are thin and rocky on steeper slopes, with claypan and loess in more level areas. More soils are derived from sandstone and loess, in contrast to interior Ozark Highlands (39) regions which have soils mainly derived from dolomite. Potential natural vegetation is a mix between Ozark species on uplands and Mississippi Alluvial Plain species in river bottoms. Land cover is predominantly forest and woodland with a scattering of pastureland and cropland in the cleared valley bottoms. This region has the highest precipitation in the Ozark Highlands (39) with 44-46 inches per year. 39k. The Prairie Ozark Border ecoregion shares characteristics with both the Wooded Osage Plains (40c) and adjacent regions within the Ozark Highlands (39). Topography is mostly smooth to gently sloping plains, and soils, derived from loess and cherty limestone, tend to support more cropland than other Ozark regions. The area shares the same bedrock, Mississippian to the north, and Ordovician to the south, as nearby Ozark regions. Streambeds are generally rocky and tend to be more Ozarkian in structure than those found in the Wooded Osage Plains (40c) to the west. The biotic composition and potential natural vegetation reflect the transition from a predominantly praire landscape in the northwest to a more wooded landscape of the interior Ozark Highlands (39).	The woodland landscape of the Ozark Highlands (39) makes an ideal habitat for the bobcat, Lynx rufus. (Photo: Jim Rathert, MDC) Ecoregions 39a, 39d, and 39k generally have more level land cleared for pasture and less closed forest area than the more dissected regions 39b, 39c, 39e, 39f, and 39g. River recreation is an important industry throughout the Ozark Highlands (39). (Photo: Nick Decker, Missouri DNR) The endangered Missouri bladder-pod, Leaquerlla filifomis, grows in open limestone glades with shallow soils and around rock outcrops. (Photo: Jim Rathert, MDC) The threatened Ozark cavefish, Amblyopsis rosae, is closely linked to the endangered gray bat. The largest Ozark cavefish populations occur in caves used by the gray bat, where the bat guano forms the caves' primary energy source. (Photo: Jim Rathert, MDC) Development along lakes and reservoirs has increased with the popularity of recreation within the Ozark Highlands (39). (Photo: Jim Rathert, MDC) Lead mining has occurred in ecoregions 39a and 39f. (Photo: Jim Rathert, MDC) The brightly colored collared lizard, Crotaphytus collaris collaris, is found in the glade habitat of the White River Hills (39c). (Photo: Jim Rathert, MDC)
40. Central Irregular Plains The Central Irregular Plains have a mix of land use and are topographically more irregular than the Western Corn Belt Plains (47) to the north, where most of the land is in crops. The region, however, is less irregular and less tree-covered than the ecoregions to the south and east. The potential natural vegetation is a grassland/woodland mosaic with wider wooded strips along the streams compared to the region to the north. The portion of the region in Iowa and the northern half of Missouri was glaciated in pre-Illinoian time. The drift, largely derived from limestone and shale, is composed of clay with a high percentage of rock fragments. The southern portion of Ecoregion 40 was not glaciated (40c and 40d), but the topography is generally level to rolling, similar to the glaciated area of this region. Soils in the southern parts of Ecoregion 40 are derived from Pennsylvanian shale, sandstone, and limestone residuum or from shallow loess. Groundwater tends to be saline, unlike the freshwater of the Ozark Highlands (39) to the southeast. The mix of land use activities includes mining operations of high-sulfur bituminous coal. Although historically mining was more widespread, a few new mines continue to open. The disturbance of these coal strata in southern Iowa, areas of northern and southwestern Missouri, and southeastern Kansas has degraded water quality and affected aquatic biota.
40a. Deep to moderate loess deposits over glacial till and dark shallow soils are characteristic of the Loess Flats and Till Plains ecoregion. Loess deposits generally increase to the south, especially near the Missouri River. Several streams have headwaters in this region, and the topography varies from flat to moderately hilly. Valley sides are not steep, with slopes generally less than 10%. The Chariton River area is a more dissected and hilly area within this region. It lacks glacial till in many places and has a greater drainage density and more woody vegetation in stream reaches than in other parts of the ecoregion. Natural wetlands occur along the Grand River and several other rivers in the region. Soils are inherently fertile, but use can be limited due to severe erosion. Land use includes areas of cropland, pasture in the valleys and on upland slopes, and bands of woodland. Corn and soybeans are the major crops. 40c. The Wooded Osage Plains ecoregion is a non-glaciated undulating plain with smooth, low, limestone escarpments and small areas of exposed bedrock. Pennsylvanian limestone, sandstone, and shale strata with differential erosion has produced a more rolling topography than in the Cherokee Plains (40d) to the south. The upland prairie has a greater proportion of southwestern plants and animals, a lesser proportion of northern species, and a greater diversity in streamside woody vegetation than the Loess Flats and Till Plains (40a) to the north. Topography of this region also tends to be smoother than the till plains of 40a. The potential natural vegetation is a mosaic of oak- hickory woodland and bluestem prairie, with a greater concentration of the woodlands than in regions to the west. Land use is a mosaic of woodland, cropland, and grassland/rangeland. 40d. The Cherokee Plains ecoregion is a non-glaciated, relatively flat, erosional plain with more poorly drained and less fertile soils than the Wooded Osage Plains (40c). Claypan soils distinguish this region from surrounding regions and support potential natural vegetation of tallgrass prairie, oak-hickory woodland, and claypan prairie where soils are less permeable. Sites can be seasonally wet but usually become extremely dry during the summers. Land use includes a mix of cropland and grassland, limited woodland, and areas of coal strip mining extending into southeastern Kansas. 40e. Well-developed claypan soils on glacial till typify the Claypan Prairie ecoregion. This region has a more level, gently rolling topography than surrounding regions. Expansive cropland and pastureland, with an emphasis on livestock production, is common. The potential natural vegetation is tallgrass prairie with less woodland than surrounding regions. Streams run generally west to east, draining into the Mississippi River, in contrast to the northwest to southeast drainage of the Loess Flats and Till Plains (40a) to the west.	The gently rolling topography of the Central Irregular Plains (40) has a land cover mosaic of cropland, woodland, and grassland. Canada geese, Branta canadensis, feed in many of the croplands of Ecoregion 40 during migration.
47. Western Corn Belt Plains 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, average annual precipitation of 26–37 inches, which occurs mainly in the growing season, and fertile, warm, moist soils make this one 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.
47a. The Northwest Iowa Loess Prairies ecoregion is a gently undulating plain with a moderate to thick layer of loess. It is the highest and driest region of the Western Corn Belt Plains, as it rises to meet the Northern Glaciated Plains (46) of the Dakotas. Although loess covers almost all of the the broad upland flats, ridges, and slopes, minor glacial till outcrops occur near the base of some of the side slopes. Silty clay loam soils have developed on the loess. The area is mostly treeless, except for the more moist areas along some stream corridors and on farmstead windbreaks. The dominant land use is cropland agriculture with some pasture and cattle feedlots. 47b. One of the youngest and flattest regions in Iowa, the Des Moines Lobe ecoregion is a distinctive area of Wisconsinan glacial stage landforms currently under extensive agriculture. In general, the land is level to gently rolling with some areas of the moraines having the most relief. The morainal ridges and hummocky knob and kettle topography contrast with the flat plains of ground moraines, former glacial lakes, and outwash deposits. A distinguishing characteristic from other parts of Ecoregion 47 is the lack of loess over the glacial drift. The stream network is poorly developed and widely spaced. The major rivers have carved valleys that are relatively deep and steep-sided. Almost all of the natural lakes of Iowa are found in the northern part of this region. Most of the region has been converted from wet prairie to agricultural use with substantial surface water drainage. Only a small fraction of the wetlands remain, and many natural lakes have been drained as a result of agricultural drainage projects. 47c. The Iowan Surface ecoregion is a geologically complex region located between the bedrock-dominated landforms of the Paleozic Plateau/Coulee Section (52b) and the relatively recent glacial drift landforms of the Des Moines Lobe (47b). The southern and southeastern border of this region is irregular and crossed by major northwest- to southeast-trending stream valleys. In the northern portion of the region, the glacial deposits are thin, and shallow limestone bedrock creates karst features such as sinkholes and sags. There are no natural lakes of glacial origin in this region, but overflow areas and backwater ponds occur on some of the larger river channels contributing to some diversity of aquatic habitat and a large number of fish species. 47d. The Missouri Alluvial Plain is part of the large, wide, flat alluvial plain found in five neighboring states. Surrounded by bluffs capped with deep loess, the historic island-studded meandering river channel has been stabilized and narrowed to manage discharge and to promote navigation and agriculture. The deep silty and clayey alluvial soils support extensive cropland agriculture. Most of the oak-hickory forest, floodplain forest, and tallgrass prairie has been removed due to conversion to cropland, although some wetlands are being restored. 47e. Rolling hills with thick loess deposits and underlying glacial till distinguish the Steeply Rolling Loess Prairies ecoregion from the flat Missouri Alluvial Plain (47d) to the west. Land clearing has promoted vast sheet erosion and gullying and consequent re-deposition of loess in the valley bottoms. Potential natural vegetation is tallgrass prairie with woodland in narrow valleys and stream reaches. Most of the region is prime farmland and cropland is extensive. 47f. Loess deposits on well drained plains and open low hills characterize the Rolling Loess Prairies ecoregion. Loess deposits tend to be thinner than those found in 47e to the west, generally less than 25 feet in depth except along the Missouri River where deposits are thicker. Potential natural vegetation is a mosaic of mostly tallgrass prairie and areas of oak-hickory forest. Although cropland agriculture is widespread, this region has more areas of woodland and pasture than neighboring 47e. 47m. 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.	The once extensive tallgrass prairie has been replaced by cropland agriculture as the prevailing land cover of the Western Corn Belt Plains (47). Large corporate farms are common and few small family farms remain in the region. The introduced ringneck pheasant, Phasianus colchicus, is a popular game bird in Ecoregion 47. Confined animal feeding operations, including hog farms, are common in many areas of the Corn Belt Plains (47). Stream ditching and drain tiling is a common land use practice associated with the widespread cropland agriculture in the Western Corn Belt Plains (47).
52. Driftless Area The hilly uplands of the Driftless Area (52) ecoregion easily distinguish it from surrounding ecoregions. Much of the area consists of a deeply dissected, loess-capped, bedrock-dominated plateau. The ecoregion is also called the Paleozoic Plateau because the landscape’s appearance is a result of erosion through rock strata of Paleozoic age. Although evidence of glacial drift has been found in the ecoregion, its influence has been minor compared to surrounding regions. Livestock and dairy farming are major land uses and can impact stream quality. In contrast to the adjacent glaciated ecoregions, the Driftless Area (52) has few lakes, most of which are reservoirs with generally high trophic states, and a stream density and flow that is generally greater than regions to the east.
52b. The bedrock-dominated terrain of the Paleozoic Plateau/Coulee Section ecoregion is strikingly different from the rest of Iowa. Steep slopes and bluffs, higher relief, sedimentary rock outcrops, dense forests, and unique boreal microhabitats differentiate this ecoregion from the Western Corn Belt Plains (47) to the west. The Silurian Escarpment, a prominent physiographic feature that helps define the southern and western boundary of this ecoregion, separates the mostly cropland area of the Western Corn Belt Plains (47) from the mixed land use of the Driftless Area (52). Dissolution of the limestone and dolomite rocks results in karst features such as sinkholes, caves, and springs, and makes groundwater vulnerable to contamination. The streams in the Iowa portion of this region occupy entrenched valleys, and have cool waters with high gradients flowing over rocky substrates. The fish communities found here reflect this preference for cool clear water with relative constancy of flow.	Woodlands and pasture dominate numerous hillsides on the bedrock influenced terrain of the Driftless Area (52) ecoregion. Cropland is confined to scattered level areas and dairy farming is common throughout the region.
72. Interior River Valleys and Hills The Interior River Valleys and Hills ecoregion is made up of many wide, flat-bottomed, terraced valleys, forested valley slopes, and dissected glacial till plains. In contrast to the generally rolling to slightly irregular plains in adjacent ecological regions to the north, east, and west (northwest only in Missouri), where most of the land is cultivated for corn and soybeans, less than half of this area is in cropland, about 30 percent is in pasture, and the remainder is in forest. This region is generally a transitional area between the more forested areas in the Ozarks, and the flatter plains and more extensive cropland of regions to the north.
72d. A small portion of the Upper Mississippi Alluvial Plain is found in Missouri, with most of the ecoregion occurring in Illinois and Iowa. The smooth to irregular alluvial plain and the river channel have undergone drastic changes in the last 100 years. Large reaches of the river have been channelized and numerous low dams with locks have been constructed upstream from St. Louis. The potential natural vegetation of oak-hickory forest, northern floodplain forest, and tallgrass prairie has all but been replaced by agriculture. Soils are deep, silty and clayey alluvium and support extensive cropland. The Mississippi River is generally less turbid than in the neighboring Middle Mississippi Alluvial Plain (72e). 72e. The Middle Mississippi Alluvial Plain in Missouri is narrow, comprising the Mississippi River alluvial plain between the Missouri and Ohio Rivers. Similar to 72d to the north, this region is a smooth alluvial plain with widespread cropland agriculture and stream channelization. Increased turbidity, current, and volume from the Missouri River contribute to a change in the aquatic biota. In addition, storm water runoff from the St. Louis urban area contributes significant non-point source pollutants to the river. 72f. Smooth to moderately dissected, forested river side-slopes and bluffs, some loess-covered hills, and areas with karst features are characteristic of the River Hills ecoregion. This region, which lies along the Missouri River as well as the Mississippi River, is a transition zone between the loess-covered and till-covered plains to the north (Ecoregion 40) and the lighter colored, rocky soils of the more dissected interior Ozark Highlands (39) regions. The River Hills are less forested than interior areas in the Ozarks. Ridges and valleys have a deep soil mantle but the steep slopes are stony with frequent rock outcrops. Loess, which can be thick in some areas, mantles the ridges and uplands. Deep, sandy and silty, moderately to poorly drained alluvium covers the river valleys. Paleozoic bedrock is relatively resistant to erosion along the Missouri River, and consequently the Missouri River alluvial valley is relatively narrow in this region, a contrast to the wide plain of neighboring 47d. Land cover throughout this region is varied, with row crops, improved pasture, woodland, and oak and mesic mixed hardwood forests.	A mix of hills, river bluffs, valleys and more level areas used for agriculture is characteristic of Ecoregion 72. (Photo: Nick Decker, Missouri DNR) Limestone bluffs, such as these along the Missouri River, are characteristic of the River Hills (72f) ecoregion. (Photo: Nick Decker, Missouri DNR)
73. Mississippi Alluvial Plain This riverine ecoregion extends from southern Illinois, at the confluence of the Ohio River with the Mississippi River, south to the Gulf of Mexico. It is mostly a broad, flat, alluvial plain with river terraces and levees providing the main elements of relief. Soils tend to be poorly drained, except for selected areas of sandy soils. In Missouri, this region is the northern biotic limit for many coastal plain species. Extensive clearing and drainage for agriculture began in the early 20th century and removed most of the natural bottomland deciduous forest. Winters are mild and summers are hot, with temperatures and average annual precipitation increasing from the north to south. Presently, most of the northern and central parts of the region are in cropland and receive heavy treatments of insecticides and herbicides. Rice, cotton, and soybeans are the major crops.
73a. The Holocene floodplain of the Mississippi alluvial valley contains the meander belt of the present course of the Mississippi River. Point bars, oxbows, natural levees, and abandoned channels are all characteristic of the Holocene Meander Belts ecoregion. Soils are silty and clayey loams derived from alluvium, are not as sandy as neighboring 73b, and are generally poorly drained. The Mississippi River and its associated tributaries have been heavily channelized and leveed throughout the region. Widespread draining of wetlands and removal of bottomland forest has also occurred and cropland agriculture is extensive. 73b. A broad, flat, alluvial plain, the Pleistocene Valley Trains ecoregion is distinct from the dissected topography of the neighboring Ozark Highlands (39). The region was formed from Pleistocene glacial outwash deposits from the Mississippi and Ohio Rivers and subsequently covered with fertile, thick, alluvial and eolian deposits. Sand dune fields and eolian deposits also occur in the plain between the Bluff Hills (Crowley’s Ridge) (74a) and the Ozark Highlands (39) to the west, and along the eastern border of Sikeston Ridge, center of the New Madrid Seismic zone. Most of the area was historically covered with bald cypress, tupelo swamp forest, and mixed deciduous bottomland forest. Natural grasslands occupied sandy terraces. Today, row crop agriculture dominates the landscape with primary production in soybeans, cotton, and rice.	Widespread cropland agriculture with blocks of forested woodlots is a common land cover throughout the Mississippi Alluvial Plain (73). (Photo: Nick Decker, Missouri DNR)
74. Mississippi Valley Loess Plains This ecoregion stretches from near the Ohio River in western Kentucky to Louisiana. It consists primarily of irregular plains, along with some disjoined low hills found within the Mississippi Alluvial Plain (73). Oak–hickory and oak-hickory-pine forests are the natural vegetation cover. With flatter topography than the Southeastern Plains ecoregion (65) to the east, streams tend to have less gradient and more silty substrates. Thick loess is a distinguishing characteristic of the region.
74a. The portion of the Bluff Hills ecoregion, locally known as Crowley’s Ridge, is a disjunct series of loesscapped low hills with greater relief than the surrounding Mississippi Alluvial Plain (73). These hills, possibly the result of movement on the New Madrid seismic zone, are geologically diverse, containing sands, gravel, clays, and bedrock of several geologic formations. Spring-fed streams and seep areas occur on the lower slopes in the sandy and gravelly soils. Soils are generally well drained, more loamy and eroded than those found in the surrounding Mississippi Alluvial Plain (73). Land cover in the Missouri portion is mainly pasture and woodland with only limited areas of row crop agriculture.	Crowley’s Ridge is a disjunct remnant of the Bluff Hills (74a) ecoregion. (Photo: David Hoffman, Missouri DNR - Geologic Survey Program)

Notes

• The full, original version of this entry is located here: http://www.epa.gov/wed/pages/ecoregions/moia_eco.htm. That description contains additional maps, as well as information on the physiography, geology, soil, potential natural vegetation, and the land use and land cover of the ecoregion.
  
• PRINCIPAL AUTHORS: Shannen S. Chapman (Dynamac Corporation), James M. Omernik (US EPA), Jerry A. Freeouf (USFS), Donald G. Huggins (KBS), James R. McCauley (KGS), Craig C. Freeman (KBS), Gerry Steinauer (NGPC), Robert T. Angelo (KDHE), and Richard L. Schlepp (USDA, NRCS).
• COLLABORATORS AND CONTRIBUTORS: Steven R. Walker (NDEQ), Kenneth R. Bazata (NDEQ), Sharon W. Waltman (USDA, NRCS-National Soil Survey Center [NSSC]), William J. Waltman (USDA, NRCS-NSSC), Roger Kanable (USDA, NRCS), Steven C. Schainost (NGPC), Craig Engelhard (USDA, NRCS), James W. Merchant (Center for Advanced Land Management Information Technologies [CALMIT], University of Missouri, Lincoln [UNL]), Virginia L. McGuire (USGS), Chris Mammoliti (KDWP), James L. Stubbendieck (UNL), David A. Mortensen (UNL), Thomas Wardle (Missouri Forest Service), David T. Lewis (UNL), Robert F. Diffendal Jr. (Missouri Conservation and Survey Division-Missouri Geological Survey) and Jeffrey A. Comstock (OAO Corporation).
• This project was partially supported by funds from the U.S. Environmental Protection Agency’s Office of Water, Biological Criteria Program.

Literature Cited

• Bailey, R.G., Avers, P.E., King, T., and McNab, W.H., eds., 1994, Ecoregions and subregions of the United States (map) (supplementary table of map unit descriptions compiled and edited by McNab, W.H. and Bailey, R.G.): Washington, D.C., U.S. Department of Agriculture - Forest Service, scale 1:7,500,000.
• Commission for Environmental Cooperation Working Group, 1997, Ecological regions of North America - toward a common perspective: Montreal, Quebec, Commission for Environmental Cooperation, 71 p.
• Gallant, A.L., Whittier, T.R., Larsen, D.P., Omernik, J.M., and Hughes, R.M., 1989, Regionalization as a tool for managing environmental resources: Corvallis, Oregon, U.S. Environmental Protection Agency EPA/600/3-89/060, 152 p.
• Griffith, G.E, Omernik, J.M., Wilton, T.F., and Pierson, S.M., 1994, Ecoregions and subregions of Iowa - a framework for water quality assessment and management: The Journal of the Iowa Academy of Science, v. 101, no. 1, p. 5-13.
• Omernik, J.M, 1987, Ecoregions of the conterminous United States (map supplement): Annals of the Association of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000.
• Omernik, J.M, 1995, Ecoregions - a framework for environmental management, in Davis, W.S. and Simon, T.P., eds., Biological assessment and criteria - tools for water resource planning and decision making: Boca Raton, Florida, Lewis Publishers, p. 49-62. ISBN: 0873718941.
• U.S. Department of Agriculture - Soil Conservation Service, 1981, Land resource regions and major land resource areas of the United States: Agriculture Handbook 296, 156 p.
• U.S. Environmental Protection Agency, 2000, Level III ecoregions of the continental United States (revision of Omernik, 1987): Corvallis, Oregon, U.S. Environmental Protection Agency - National Health and Environmental Effects Research Laboratory Map M-1, various scales.
• Wiken, E, 1986, Terrestrial ecozones of Canada: Ottawa, Environment Canada, Ecological Land Classification Series no. 19, 26 p. ISBN: 0662147618.

Ecoregions of Iowa and Missouri.

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources; they are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. Ecoregions are directly applicable to the immediate needs of state agencies, including the development of biological criteria and water quality standards, and the establishment of management goals for nonpoint-source pollution. They are also relevant to integrated ecosystem management, an ultimate goal of most federal and state resource management agencies.

The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of the patterns of biotic and abiotic phenomena that reflect differences in ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I and level II divide the North American continent into 15 and 52 regions, respectively (Commission for Environmental Cooperation Working Group 1997). At level III, the continental United States contains 104 regions (United States Environmental Protection Agency [US EPA], 2000). However, depending on the objectives of a particular project, ecoregions may be aggregated within levels of the hierarchy for data analysis and interpretation. Explanations of the methods used to define the US EPA’s ecoregions are given in Omernik (1995), Griffith and others (1994), and Gallant and others (1989).

Level III Ecoregions of the Conterminous United States. (Map source: USEPA, 2000)

This level III and IV ecoregion map was compiled at a 1:250,000-scale; it depicts revisions and subdivisions of earlier level III ecoregions that were originally compiled at a smaller scale (US EPA, 2000; Omernik, 1987). This poster is the product of a collaborative effort primarily between the US EPA Region VII, the US EPA National Health and Environmental Effects Research Laboratory (Corvallis, Oregon), the Missouri Department of Environmental Quality (NDEQ), the Missouri Game and Parks Commission (NGPC), the Iowa Biological Survey (KBS), the Iowa Geological Survey (KGS), the Iowa Department of Health and Environment, Division of Environment (KDHE), Iowa Department of Wildlife and Parks (KDWP), the United States Department of Agriculture - Natural Resources Conservation Service (NRCS) (formerly the Soil Conservation Service), and the United States Department of the Interior - U.S. Geological Survey (USGS) - Earth Resources Observation Systems (EROS) Data Center.

This project is associated with an interagency effort to develop a common framework of ecological regions. Reaching that objective requires recognition of the differences in the conceptual approaches and mapping methodologies that have been used to develop the most commonly used existing ecoregion-type frameworks, including those developed by the USFS (United States Forest Service) (Bailey and others, 1994), the US EPA (Omernik, 1987, 1995), and the NRCS (United States Department of Agriculture - Soil Conservation Service, 1981). As each of these frameworks is further developed, the differences between them lessen. Regional collaborative projects such as this one in Missouri and Iowa, where agreement can be reached among multiple resource management agencies, is a step in the direction of attaining commonality and consistency in ecoregion frameworks for the entire nation.

39. Ozark Highlands The Ozark Highlands ecoregion has a more irregular physiography and is generally more forested than adjacent regions, with the exception of the Boston Mountains (38) to the south. Soils are mostly derived from cherty carbonate rocks, with chert stone comprising about 20% to 60% of the soil mass. Cambrian and Ordovician dolomite and sandstone comprise the dominant bedrock in the interior of the region with Mississippian limestone underlying the western outer regions. Shale, chert, and Precambrian igneous rocks are also present. Topography varies from steep slopes near the large streams to moderate relief hills on the broad plateaus or inter-stream areas. Karst features, including caves, springs, and spring-fed streams are found throughout most of the region. High-gradient, clear-flowing streams in entrenched valley meanders are also common. More than 60% of the total area is open forest or woodland, although in the more rugged sections the forest covers nearly all of the upland. Oak is the predominant forest type, but mixed stands of oak and pine are also common, with pine concentrations greatest to the southeast. Cultivated land is mainly confined to small tracts in the numerous valleys and small creek bottoms. Cleared upland is used for pasture and livestock.
39a. The Springfield Plateau ecoregion is a smooth to gently rolling plain underlain by Mississippian-age cherty limestone and is less dissected than most regions in the Ozarks. A moderate topography and a potential natural vegetation of tallgrass prairie, deciduous forest, and savanna characterize this transitional area where the prairies of the Cherokee Plains (40d) grade into the woodlands of the Ozarks. However, unlike the neighboring plains, this region has karst features and rocky soils, especially in wooded areas. Land cover is a mix of woodland and areas of pastureland in the cleared prairies. Lead and zinc were mined in the southwest portion of this region and mining tailings still remain. 39b. The Elk River Hills ecoregion includes areas of rolling plains and more rugged hills with steep slopes and narrow ridges than the neighboring Springfield Plateau (39a). Soils are rocky and thin over carbonate bedrock and support potential natural vegetation of oak woodland, savanna and some limited glade areas, with prairie comprising only about 7% of the area. This marks a transition from the greater prairie component of the Springfield Plateau (39a), to the mixed oak woodland, scattered pine-oak and glades of the White River Hills (39c) to the east. This region currently has substantial areas in poultry production, especially across the Missouri border into Arkansas, which have impacted water quality. 39c. The White River Hills ecoregion is one of the more dissected areas in the Ozark region with local relief of 200 to 600 feet. Dissected Ordovician dolomite and some sandstone, with step-like topography of level-crested buttes, lower benches, and bottomlands are common. Potential natural vegetation is a mosaic of oak and oak-pine forest and woodland, interspersed with widespread limestone or dolomite glades. Cliffs, sinkholes, and caves are prevalent, with some of the largest caves in Missouri found in this region. Large springs, high-gradient, sustained-flow streams, as well as many smaller losing streams that are often dry are typical. There are significant water impoundments in this ecoregion with the entire length of the White River in Missouri impounded into three reservoirs (Table Rock Lake, Bull Shoals Lake, and Lake Taneycomo). The dissected topography and the thin, rocky soils provide little arable land. Consequently, land cover is principally woodland and much of the area is in public lands. 39d. Surrounded by hill regions, except for the Springfield Plateau (39a) to the west, the Central Plateau ecoregion is less dissected than most regions in the interior Ozark Highlands. Streams flowing across the region have divided it into a large number of small plateaus. Pennsylvanian strata underlie low relief areas in the north. Most of the surface, however, is underlain by Ordovician carbonates. Bedrock is mantled by a thick solution residuum and loess, and karst features are extensive with large sinkhole areas. The potential natural vegetation of this region is tallgrass prairie, savanna, and post-oak woodlands, with a larger area of prairie vegetation than neighboring regions. The majority of the land is cleared and used for pasture; farms are found mainly on the uplands. Cherty soils predominate, although they are not as cherty as in surrounding hill regions. Large areas of clay and sandy soils also occur and areas with Pennsylvanian clay-filled sinks are mined for fire clay. The region has less surface water and soils are generally more droughty than in surrounding regions. 39e. The Osage/Gasconade Hills ecoregion is more densely forested and dissected than the lower relief Central Plateau (39d) to the south. Steep slopes and narrow ridges of carbonate and sandstone underlie soils which are rocky and thin. Outcrops of Gasconade dolomite with some sandstone are found throughout the region along with areas of Roubidoux sandstone, Jefferson City-Cotter dolomites and scattered Mississippian limestone outliers in the western portion. Numerous caves, springs, calcareous wet meadows, losing streams, and streams with entrenched valley meanders are common. Streams flow generally northward and drain into the Missouri River. The potential natural vegetation is predominantly mixed oak forest, with oak-pine forest and some pine forests in the southeast areas of the region and some small limestone and sandstone glades. The northeastern edges of this region are transitional and blend into the Interior River Valleys and Hills (72) ecoregion. 39f. The St. Francois Knobs and Basins ecoregion contains the oldest geologic formations in the state and has a different landscape than surrounding regions. The igneous bedrock knobs of Precambrian granite, rhyolite, and intermediate rocks rise 200 to 900 feet above the intervening basins which are underlain by Cambrian sedimentary rocks, primarily carbonate with some sandstone. This is the only region within the Ozark Highlands (39) that generally lacks karst topography. Streams are smaller than in neighboring regions but have a greater fall distance because of the steep topography. Sedimentary-derived soils may be stone free, not cherty as in neighboring regions. The soil mantle is generally shallow with low fertility, except in the basins, which have a thicker, more loamy layer. The potential natural vegetation includes scrub-oak, post-oak, and blackjack oak forests and glade areas, along with prairie in the basins and valleys. Most of the region is in forest and woodland, with cleared land limited to the small basin-like valleys used for pasture and limited cropland. Lead mining has been an important activity in this region for over two centuries and significant scarification has occurred. Other mineral resources include granite and, to a limited extent, silver, copper, and cobalt, by-products of lead mining. 39g. The Meramec River Hills ecoregion is deeply dissected, with steep-sided hills and chert-covered ridges. The hills tend to be more rugged than in the Osage/Gasconade Hills (39e) ecoregion to the northwest. Land use is mainly timber and recreation, with some pastureland for grazing, and barite and iron mining in the southeast. The potential natural vegetation in this region is shortleaf pine-oak forest and woodland, with a greater oak concentration than in forests of the Current River Hills (39h) to the south. Streams in this region drain northeast into the Mississippi River. 39h. In many ways, the physiography of the Current River Hills ecoregion is similar to that of the Meramec River Hills (39g) to the north. However, this region has many endemic species not found in other Ozark regions and the potential natural vegetation here has a greater pine concentration than in regions to the north and west. The region underwent intensive timber cutting in the early decades of the twentieth century. It now sustains major recreational activities. The stream valleys contain numerous, large, high-quality springs and water quality is generally better than elsewhere in Missouri. Caves and losing streams are common. Streams drain southeast into the Mississippi River. 39i. The Eastern Ozark Border ecoregion is a transitional area between the interior ecoregions of the Ozark Highlands (39) and the Interior River Valleys and Hills (72) ecoregion to the east. Moderately dissected hills and sheer bluffs typify the region. Soils can be rocky and thin on steep slopes, with areas of claypan or loess similar to the Black River Hills Border (39j) to the southwest. Compared to the Central Plateau (39d), however, the loess mantle in this region tends to be deeper and more expansive on the uplands. Potential natural vegetation is a mix of oak forest, savanna, glades, and prairies. Land cover is variable with forests, woodlands, and cleared areas in cropland and pasture. This ecoregion has more cropland agriculture than adjoining Ozark regions (39j, 39f). 39j. The Black River Hills Border is a transitional region with broad, flat inter-stream divides and moderately dissected hills. There is significantly less relief than in neighboring hill regions in the Ozark Highlands (39) but greater relief than in the southeastern Mississippi Alluvial Plain (73). Soils are thin and rocky on steeper slopes, with claypan and loess in more level areas. More soils are derived from sandstone and loess, in contrast to interior Ozark Highlands (39) regions which have soils mainly derived from dolomite. Potential natural vegetation is a mix between Ozark species on uplands and Mississippi Alluvial Plain species in river bottoms. Land cover is predominantly forest and woodland with a scattering of pastureland and cropland in the cleared valley bottoms. This region has the highest precipitation in the Ozark Highlands (39) with 44-46 inches per year. 39k. The Prairie Ozark Border ecoregion shares characteristics with both the Wooded Osage Plains (40c) and adjacent regions within the Ozark Highlands (39). Topography is mostly smooth to gently sloping plains, and soils, derived from loess and cherty limestone, tend to support more cropland than other Ozark regions. The area shares the same bedrock, Mississippian to the north, and Ordovician to the south, as nearby Ozark regions. Streambeds are generally rocky and tend to be more Ozarkian in structure than those found in the Wooded Osage Plains (40c) to the west. The biotic composition and potential natural vegetation reflect the transition from a predominantly praire landscape in the northwest to a more wooded landscape of the interior Ozark Highlands (39).	The woodland landscape of the Ozark Highlands (39) makes an ideal habitat for the bobcat, Lynx rufus. (Photo: Jim Rathert, MDC) Ecoregions 39a, 39d, and 39k generally have more level land cleared for pasture and less closed forest area than the more dissected regions 39b, 39c, 39e, 39f, and 39g. River recreation is an important industry throughout the Ozark Highlands (39). (Photo: Nick Decker, Missouri DNR) The endangered Missouri bladder-pod, Leaquerlla filifomis, grows in open limestone glades with shallow soils and around rock outcrops. (Photo: Jim Rathert, MDC) The threatened Ozark cavefish, Amblyopsis rosae, is closely linked to the endangered gray bat. The largest Ozark cavefish populations occur in caves used by the gray bat, where the bat guano forms the caves' primary energy source. (Photo: Jim Rathert, MDC) Development along lakes and reservoirs has increased with the popularity of recreation within the Ozark Highlands (39). (Photo: Jim Rathert, MDC) Lead mining has occurred in ecoregions 39a and 39f. (Photo: Jim Rathert, MDC) The brightly colored collared lizard, Crotaphytus collaris collaris, is found in the glade habitat of the White River Hills (39c). (Photo: Jim Rathert, MDC)
40. Central Irregular Plains The Central Irregular Plains have a mix of land use and are topographically more irregular than the Western Corn Belt Plains (47) to the north, where most of the land is in crops. The region, however, is less irregular and less tree-covered than the ecoregions to the south and east. The potential natural vegetation is a grassland/woodland mosaic with wider wooded strips along the streams compared to the region to the north. The portion of the region in Iowa and the northern half of Missouri was glaciated in pre-Illinoian time. The drift, largely derived from limestone and shale, is composed of clay with a high percentage of rock fragments. The southern portion of Ecoregion 40 was not glaciated (40c and 40d), but the topography is generally level to rolling, similar to the glaciated area of this region. Soils in the southern parts of Ecoregion 40 are derived from Pennsylvanian shale, sandstone, and limestone residuum or from shallow loess. Groundwater tends to be saline, unlike the freshwater of the Ozark Highlands (39) to the southeast. The mix of land use activities includes mining operations of high-sulfur bituminous coal. Although historically mining was more widespread, a few new mines continue to open. The disturbance of these coal strata in southern Iowa, areas of northern and southwestern Missouri, and southeastern Kansas has degraded water quality and affected aquatic biota.
40a. Deep to moderate loess deposits over glacial till and dark shallow soils are characteristic of the Loess Flats and Till Plains ecoregion. Loess deposits generally increase to the south, especially near the Missouri River. Several streams have headwaters in this region, and the topography varies from flat to moderately hilly. Valley sides are not steep, with slopes generally less than 10%. The Chariton River area is a more dissected and hilly area within this region. It lacks glacial till in many places and has a greater drainage density and more woody vegetation in stream reaches than in other parts of the ecoregion. Natural wetlands occur along the Grand River and several other rivers in the region. Soils are inherently fertile, but use can be limited due to severe erosion. Land use includes areas of cropland, pasture in the valleys and on upland slopes, and bands of woodland. Corn and soybeans are the major crops. 40c. The Wooded Osage Plains ecoregion is a non-glaciated undulating plain with smooth, low, limestone escarpments and small areas of exposed bedrock. Pennsylvanian limestone, sandstone, and shale strata with differential erosion has produced a more rolling topography than in the Cherokee Plains (40d) to the south. The upland prairie has a greater proportion of southwestern plants and animals, a lesser proportion of northern species, and a greater diversity in streamside woody vegetation than the Loess Flats and Till Plains (40a) to the north. Topography of this region also tends to be smoother than the till plains of 40a. The potential natural vegetation is a mosaic of oak- hickory woodland and bluestem prairie, with a greater concentration of the woodlands than in regions to the west. Land use is a mosaic of woodland, cropland, and grassland/rangeland. 40d. The Cherokee Plains ecoregion is a non-glaciated, relatively flat, erosional plain with more poorly drained and less fertile soils than the Wooded Osage Plains (40c). Claypan soils distinguish this region from surrounding regions and support potential natural vegetation of tallgrass prairie, oak-hickory woodland, and claypan prairie where soils are less permeable. Sites can be seasonally wet but usually become extremely dry during the summers. Land use includes a mix of cropland and grassland, limited woodland, and areas of coal strip mining extending into southeastern Kansas. 40e. Well-developed claypan soils on glacial till typify the Claypan Prairie ecoregion. This region has a more level, gently rolling topography than surrounding regions. Expansive cropland and pastureland, with an emphasis on livestock production, is common. The potential natural vegetation is tallgrass prairie with less woodland than surrounding regions. Streams run generally west to east, draining into the Mississippi River, in contrast to the northwest to southeast drainage of the Loess Flats and Till Plains (40a) to the west.	The gently rolling topography of the Central Irregular Plains (40) has a land cover mosaic of cropland, woodland, and grassland. Canada geese, Branta canadensis, feed in many of the croplands of Ecoregion 40 during migration.
47. Western Corn Belt Plains 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, average annual precipitation of 26–37 inches, which occurs mainly in the growing season, and fertile, warm, moist soils make this one 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.
47a. The Northwest Iowa Loess Prairies ecoregion is a gently undulating plain with a moderate to thick layer of loess. It is the highest and driest region of the Western Corn Belt Plains, as it rises to meet the Northern Glaciated Plains (46) of the Dakotas. Although loess covers almost all of the the broad upland flats, ridges, and slopes, minor glacial till outcrops occur near the base of some of the side slopes. Silty clay loam soils have developed on the loess. The area is mostly treeless, except for the more moist areas along some stream corridors and on farmstead windbreaks. The dominant land use is cropland agriculture with some pasture and cattle feedlots. 47b. One of the youngest and flattest regions in Iowa, the Des Moines Lobe ecoregion is a distinctive area of Wisconsinan glacial stage landforms currently under extensive agriculture. In general, the land is level to gently rolling with some areas of the moraines having the most relief. The morainal ridges and hummocky knob and kettle topography contrast with the flat plains of ground moraines, former glacial lakes, and outwash deposits. A distinguishing characteristic from other parts of Ecoregion 47 is the lack of loess over the glacial drift. The stream network is poorly developed and widely spaced. The major rivers have carved valleys that are relatively deep and steep-sided. Almost all of the natural lakes of Iowa are found in the northern part of this region. Most of the region has been converted from wet prairie to agricultural use with substantial surface water drainage. Only a small fraction of the wetlands remain, and many natural lakes have been drained as a result of agricultural drainage projects. 47c. The Iowan Surface ecoregion is a geologically complex region located between the bedrock-dominated landforms of the Paleozic Plateau/Coulee Section (52b) and the relatively recent glacial drift landforms of the Des Moines Lobe (47b). The southern and southeastern border of this region is irregular and crossed by major northwest- to southeast-trending stream valleys. In the northern portion of the region, the glacial deposits are thin, and shallow limestone bedrock creates karst features such as sinkholes and sags. There are no natural lakes of glacial origin in this region, but overflow areas and backwater ponds occur on some of the larger river channels contributing to some diversity of aquatic habitat and a large number of fish species. 47d. The Missouri Alluvial Plain is part of the large, wide, flat alluvial plain found in five neighboring states. Surrounded by bluffs capped with deep loess, the historic island-studded meandering river channel has been stabilized and narrowed to manage discharge and to promote navigation and agriculture. The deep silty and clayey alluvial soils support extensive cropland agriculture. Most of the oak-hickory forest, floodplain forest, and tallgrass prairie has been removed due to conversion to cropland, although some wetlands are being restored. 47e. Rolling hills with thick loess deposits and underlying glacial till distinguish the Steeply Rolling Loess Prairies ecoregion from the flat Missouri Alluvial Plain (47d) to the west. Land clearing has promoted vast sheet erosion and gullying and consequent re-deposition of loess in the valley bottoms. Potential natural vegetation is tallgrass prairie with woodland in narrow valleys and stream reaches. Most of the region is prime farmland and cropland is extensive. 47f. Loess deposits on well drained plains and open low hills characterize the Rolling Loess Prairies ecoregion. Loess deposits tend to be thinner than those found in 47e to the west, generally less than 25 feet in depth except along the Missouri River where deposits are thicker. Potential natural vegetation is a mosaic of mostly tallgrass prairie and areas of oak-hickory forest. Although cropland agriculture is widespread, this region has more areas of woodland and pasture than neighboring 47e. 47m. 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.	The once extensive tallgrass prairie has been replaced by cropland agriculture as the prevailing land cover of the Western Corn Belt Plains (47). Large corporate farms are common and few small family farms remain in the region. The introduced ringneck pheasant, Phasianus colchicus, is a popular game bird in Ecoregion 47. Confined animal feeding operations, including hog farms, are common in many areas of the Corn Belt Plains (47). Stream ditching and drain tiling is a common land use practice associated with the widespread cropland agriculture in the Western Corn Belt Plains (47).
52. Driftless Area The hilly uplands of the Driftless Area (52) ecoregion easily distinguish it from surrounding ecoregions. Much of the area consists of a deeply dissected, loess-capped, bedrock-dominated plateau. The ecoregion is also called the Paleozoic Plateau because the landscape’s appearance is a result of erosion through rock strata of Paleozoic age. Although evidence of glacial drift has been found in the ecoregion, its influence has been minor compared to surrounding regions. Livestock and dairy farming are major land uses and can impact stream quality. In contrast to the adjacent glaciated ecoregions, the Driftless Area (52) has few lakes, most of which are reservoirs with generally high trophic states, and a stream density and flow that is generally greater than regions to the east.
52b. The bedrock-dominated terrain of the Paleozoic Plateau/Coulee Section ecoregion is strikingly different from the rest of Iowa. Steep slopes and bluffs, higher relief, sedimentary rock outcrops, dense forests, and unique boreal microhabitats differentiate this ecoregion from the Western Corn Belt Plains (47) to the west. The Silurian Escarpment, a prominent physiographic feature that helps define the southern and western boundary of this ecoregion, separates the mostly cropland area of the Western Corn Belt Plains (47) from the mixed land use of the Driftless Area (52). Dissolution of the limestone and dolomite rocks results in karst features such as sinkholes, caves, and springs, and makes groundwater vulnerable to contamination. The streams in the Iowa portion of this region occupy entrenched valleys, and have cool waters with high gradients flowing over rocky substrates. The fish communities found here reflect this preference for cool clear water with relative constancy of flow.	Woodlands and pasture dominate numerous hillsides on the bedrock influenced terrain of the Driftless Area (52) ecoregion. Cropland is confined to scattered level areas and dairy farming is common throughout the region.
72. Interior River Valleys and Hills The Interior River Valleys and Hills ecoregion is made up of many wide, flat-bottomed, terraced valleys, forested valley slopes, and dissected glacial till plains. In contrast to the generally rolling to slightly irregular plains in adjacent ecological regions to the north, east, and west (northwest only in Missouri), where most of the land is cultivated for corn and soybeans, less than half of this area is in cropland, about 30 percent is in pasture, and the remainder is in forest. This region is generally a transitional area between the more forested areas in the Ozarks, and the flatter plains and more extensive cropland of regions to the north.
72d. A small portion of the Upper Mississippi Alluvial Plain is found in Missouri, with most of the ecoregion occurring in Illinois and Iowa. The smooth to irregular alluvial plain and the river channel have undergone drastic changes in the last 100 years. Large reaches of the river have been channelized and numerous low dams with locks have been constructed upstream from St. Louis. The potential natural vegetation of oak-hickory forest, northern floodplain forest, and tallgrass prairie has all but been replaced by agriculture. Soils are deep, silty and clayey alluvium and support extensive cropland. The Mississippi River is generally less turbid than in the neighboring Middle Mississippi Alluvial Plain (72e). 72e. The Middle Mississippi Alluvial Plain in Missouri is narrow, comprising the Mississippi River alluvial plain between the Missouri and Ohio Rivers. Similar to 72d to the north, this region is a smooth alluvial plain with widespread cropland agriculture and stream channelization. Increased turbidity, current, and volume from the Missouri River contribute to a change in the aquatic biota. In addition, storm water runoff from the St. Louis urban area contributes significant non-point source pollutants to the river. 72f. Smooth to moderately dissected, forested river side-slopes and bluffs, some loess-covered hills, and areas with karst features are characteristic of the River Hills ecoregion. This region, which lies along the Missouri River as well as the Mississippi River, is a transition zone between the loess-covered and till-covered plains to the north (Ecoregion 40) and the lighter colored, rocky soils of the more dissected interior Ozark Highlands (39) regions. The River Hills are less forested than interior areas in the Ozarks. Ridges and valleys have a deep soil mantle but the steep slopes are stony with frequent rock outcrops. Loess, which can be thick in some areas, mantles the ridges and uplands. Deep, sandy and silty, moderately to poorly drained alluvium covers the river valleys. Paleozoic bedrock is relatively resistant to erosion along the Missouri River, and consequently the Missouri River alluvial valley is relatively narrow in this region, a contrast to the wide plain of neighboring 47d. Land cover throughout this region is varied, with row crops, improved pasture, woodland, and oak and mesic mixed hardwood forests.	A mix of hills, river bluffs, valleys and more level areas used for agriculture is characteristic of Ecoregion 72. (Photo: Nick Decker, Missouri DNR) Limestone bluffs, such as these along the Missouri River, are characteristic of the River Hills (72f) ecoregion. (Photo: Nick Decker, Missouri DNR)
73. Mississippi Alluvial Plain This riverine ecoregion extends from southern Illinois, at the confluence of the Ohio River with the Mississippi River, south to the Gulf of Mexico. It is mostly a broad, flat, alluvial plain with river terraces and levees providing the main elements of relief. Soils tend to be poorly drained, except for selected areas of sandy soils. In Missouri, this region is the northern biotic limit for many coastal plain species. Extensive clearing and drainage for agriculture began in the early 20th century and removed most of the natural bottomland deciduous forest. Winters are mild and summers are hot, with temperatures and average annual precipitation increasing from the north to south. Presently, most of the northern and central parts of the region are in cropland and receive heavy treatments of insecticides and herbicides. Rice, cotton, and soybeans are the major crops.
73a. The Holocene floodplain of the Mississippi alluvial valley contains the meander belt of the present course of the Mississippi River. Point bars, oxbows, natural levees, and abandoned channels are all characteristic of the Holocene Meander Belts ecoregion. Soils are silty and clayey loams derived from alluvium, are not as sandy as neighboring 73b, and are generally poorly drained. The Mississippi River and its associated tributaries have been heavily channelized and leveed throughout the region. Widespread draining of wetlands and removal of bottomland forest has also occurred and cropland agriculture is extensive. 73b. A broad, flat, alluvial plain, the Pleistocene Valley Trains ecoregion is distinct from the dissected topography of the neighboring Ozark Highlands (39). The region was formed from Pleistocene glacial outwash deposits from the Mississippi and Ohio Rivers and subsequently covered with fertile, thick, alluvial and eolian deposits. Sand dune fields and eolian deposits also occur in the plain between the Bluff Hills (Crowley’s Ridge) (74a) and the Ozark Highlands (39) to the west, and along the eastern border of Sikeston Ridge, center of the New Madrid Seismic zone. Most of the area was historically covered with bald cypress, tupelo swamp forest, and mixed deciduous bottomland forest. Natural grasslands occupied sandy terraces. Today, row crop agriculture dominates the landscape with primary production in soybeans, cotton, and rice.	Widespread cropland agriculture with blocks of forested woodlots is a common land cover throughout the Mississippi Alluvial Plain (73). (Photo: Nick Decker, Missouri DNR)
74. Mississippi Valley Loess Plains This ecoregion stretches from near the Ohio River in western Kentucky to Louisiana. It consists primarily of irregular plains, along with some disjoined low hills found within the Mississippi Alluvial Plain (73). Oak–hickory and oak-hickory-pine forests are the natural vegetation cover. With flatter topography than the Southeastern Plains ecoregion (65) to the east, streams tend to have less gradient and more silty substrates. Thick loess is a distinguishing characteristic of the region.
74a. The portion of the Bluff Hills ecoregion, locally known as Crowley’s Ridge, is a disjunct series of loesscapped low hills with greater relief than the surrounding Mississippi Alluvial Plain (73). These hills, possibly the result of movement on the New Madrid seismic zone, are geologically diverse, containing sands, gravel, clays, and bedrock of several geologic formations. Spring-fed streams and seep areas occur on the lower slopes in the sandy and gravelly soils. Soils are generally well drained, more loamy and eroded than those found in the surrounding Mississippi Alluvial Plain (73). Land cover in the Missouri portion is mainly pasture and woodland with only limited areas of row crop agriculture.	Crowley’s Ridge is a disjunct remnant of the Bluff Hills (74a) ecoregion. (Photo: David Hoffman, Missouri DNR - Geologic Survey Program)

Notes

• The full, original version of this entry is located here: http://www.epa.gov/wed/pages/ecoregions/moia_eco.htm. That description contains additional maps, as well as information on the physiography, geology, soil, potential natural vegetation, and the land use and land cover of the ecoregion.
  
• PRINCIPAL AUTHORS: Shannen S. Chapman (Dynamac Corporation), James M. Omernik (US EPA), Jerry A. Freeouf (USFS), Donald G. Huggins (KBS), James R. McCauley (KGS), Craig C. Freeman (KBS), Gerry Steinauer (NGPC), Robert T. Angelo (KDHE), and Richard L. Schlepp (USDA, NRCS).
• COLLABORATORS AND CONTRIBUTORS: Steven R. Walker (NDEQ), Kenneth R. Bazata (NDEQ), Sharon W. Waltman (USDA, NRCS-National Soil Survey Center [NSSC]), William J. Waltman (USDA, NRCS-NSSC), Roger Kanable (USDA, NRCS), Steven C. Schainost (NGPC), Craig Engelhard (USDA, NRCS), James W. Merchant (Center for Advanced Land Management Information Technologies [CALMIT], University of Missouri, Lincoln [UNL]), Virginia L. McGuire (USGS), Chris Mammoliti (KDWP), James L. Stubbendieck (UNL), David A. Mortensen (UNL), Thomas Wardle (Missouri Forest Service), David T. Lewis (UNL), Robert F. Diffendal Jr. (Missouri Conservation and Survey Division-Missouri Geological Survey) and Jeffrey A. Comstock (OAO Corporation).
• This project was partially supported by funds from the U.S. Environmental Protection Agency’s Office of Water, Biological Criteria Program.

Literature Cited

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