Northern Prairie Wildlife Research Center
Management of Agricultural Landscapes for the Conservation of Neotropical
Recent Changes in Agricultural Habitats and Landscape Structure
The changes in agricultural landscapes that most concern conservation biologists
are those that have occurred on a large spatial scale. We focus on changes in
agricultural habitats in the last three decades, when bird-population trends
in the Midwest were well documented (Herkert 1995). The major habitats in the
Midwest are crops, including small grains (wheat, oats, etc.), corn, soybeans,
sunflowers, and forage (hay). Other habitats are pastureland and rangeland,
wetlands, woodlands, and strip cover (e.g., fencerows, roadsides, waterways,
terraces). Idle cropland is not explicitly considered a habitat in this section
but is covered below under land-use practices. The amounts and relative proportions
of cropland, pastureland and rangeland, woodland, and other rural land vary
across the Midwest (table 2).
Table 2. Estimated land use (thousands of hectares)
of non-federal, rural land in the 12 midwestern States in 1992 (USDA 1994).
Pastureland includes rangeland and excludes grazed forested land. Land enrolled
in the Conservation Reserve Program is included with other rural land.
| Region State
| Corn Belt
| Lake States
| Northern Plains
The total area of cropland in the Midwest in the early 1980's was similar to
that in the late 1940's (Frey and Hexem 1985). There was a steady decline in
cropland area, associated with surplus production, from the late 1940's to the
mid-1970's. The area then increased until the early 1980's, as exports expanded.
The pattern of change varied geographically. The area used for crops in the
Northern Plains (Kansas, Nebraska, North Dakota, South Dakota) in the early
1980's was similar to that in the late 1940's. In the Corn Belt (Illinois, Indiana,
Iowa, Missouri, Ohio), there was a dip in the mid-1970's but an increase of
9.5% between the late 1940's and early 1980's. In the Lake States (Michigan,
Minnesota, Wisconsin), there was an increase of 2.1% over the same period. The
area of active cropland in the Midwest declined again from 1982 to 1992, mostly
due to enrollment of cropland in the Conservation Reserve Program (CRP; USDA
Analysis of data from the National Resources Inventory (NRI), which has
been conducted since 1967, also demonstrates declines in cropland area in
the Midwest between 1967 and 1977 and between 1982 and 1992 (fig. 1). Analysis
procedures changed between 1977 and 1982, so inventory data before 1977 cannot
be directly compared with data after 1982 (USDA 1990).
Figure 1. Recent changes in estimated land use of non-federal,
rural land in three midwestern regions (USDA 1971b, 1982a, 1994). "Pastureland
& Rangeland" excludes grazed forested land. Analysis procedures changed between
1977 and 1982, so inventory data before 1977 cannot be directly compared with
data after 1982 (USDA 1990).
With the exception of the CRP, changes in the total area of midwestern cropland
have been relatively small, particularly during the last three decades, when
the best bird-survey data have been available (Herkert 1995). We focus on these
decades in our presentation of changes at the level of major habitats.
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