Iowa's Ecological Regions
Ecoregions denote areas of general similarity in ecosystems and in the type,
quality, and quantity of environmental resources. An ecoregion is identified
through patterns and composition of both biological and physical
characteristics, including geology, physiography, vegetation, climate, soils,
land use, wildlife, and hydrology. The interactions and relative importance of
each of these components varies between ecoregions, creating a unique ecosystem
within each region.
There are 10 ecoregions and subecoregions within the state of Iowa:
- 40-- Loess Flats and Till Plains
- 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.
- 47a-- Northwest Iowa Loess Prairies
- 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
of the Dakotas. Although loess covers almost all of 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-- Des Moines Lobe
- 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-- Iowan Surface
- The Iowan Surface ecoregion is a geologically complex region located between
the bedrock-dominated landforms of the Paleozoic Plateau region and the
relatively recent glacial drift landforms of the Des Moines Lobe. The southern
and southeastern border of this ecoregion 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-- Missouri Alluvial Plain
- 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
- 47e-- Steeply Rolling Prairies
- Rolling hills with thick loess deposits and underlying glacial till
distinguish the Steeply Rolling Loess Prairies ecoregion from the flat Missouri
Alluvial Plain 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-- Rolling Loess Prairies
- Loess deposits on well drained plains and open low hills characterize the
Rolling Loess Prairies ecoregion. Loess deposits tend to be thinner than those
find in the Steeply Rolling Loess Prairies 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 the areas to the west.
- 47m-- Western Loess Hills
- 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 to
the east. The more irregular topography and erosive, silty soils contributed 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.
- 52-- Paleozoic Plateau
- The bedrock-dominated terrain of the Paleozoic Plateau 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 Cornbelt Plains to
the west. The Silurian Escarpment, a prominent physiographic feature that helps
define the southern and western boundary this ecoregion, separates the mostly
cropland area of the west from the mixed land use of the Driftless Area.
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 consistency of flow.
- 72-- Interior River Lowland
- 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 of 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 Missouri portions of the region.