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4.1 Historical Land Use

4.1.1 Land Use Databases

Major Land Uses Database-- This database contains land uses by major category for each Census of Agriculture year (roughly every 5 years) between 1945 and 1992. The database was constructed by the USDA Economic Research Service. To document general trends in land use for the South, we report data for the 11 entire Southern States within the region. Texas and Oklahoma are excluded because only small portions of these States are in the Assessment area and the portions not included have very different ecological conditions. Including totals for Texas and Oklahoma therefore would significantly skew the results.

We report land uses by the following categories:

1. Cropland: This category includes cropland harvested, crop failure, cultivated summer fallow, cropland used only for pasture, and idle cropland.




2. Pasture: This category includes all open land used primarily for pasture and grazing. Forested pasture is included under forestland.




3. Forestland: This category is generally consistent with USDA Forest Service definitions of forest. It includes land at least 10 percent stocked by trees of any size and land formerly having had such tree cover that will be naturally or artificially regenerated. These data are not necessarily consistent with Forest Service estimates of forestland area due to differences in classification of dominant land use. In spite of these differences, estimates provide a useful means for examining regional trends in forest area consistent with changes in other land-use categories.




4. Urban plus rural transportation: Urban areas are incorporated and unincorporated places of 2,500 or more people. Rural transportation corridors include highways, roads, and railroad rights-of-way plus airport facilities.




5. All other: The difference between categories 1-4 and total land area.

National Resource Inventory (NRI). The NRI is a multiresource inventory conducted on nonfederal lands by the USDA Natural Resources Conservation Service (NRCS). The NRI was conducted in 1982, 1987, 1992, and 1997. The inventory uses a statistically based sample of plots with information compiled on land cover or use, wetlands, habitat diversity, etc... We report land-use data aggregated to the county and the ecological section levels.

Definitions of land-use categories are somewhat different from those used in the Major Land Uses Database described above. We report NRI land uses by the following four categories:

1. Agriculture: cultivated and uncultivated cropland plus pasture.




2. Forestland: area that is "...at least 10 percent stocked by single-stemmed woody species of any size that will be at least 4 meters tall (13 feet) at maturity. Also included is land bearing evidence of natural regeneration of tree cover and not currently developed for nonforest use (National Cartography and Geospatial Center 1998)."




3. Urban and Built Up Areas. "A land cover category consisting of residential, industrial, commercial, and institutional land; construction sites; public administrative sites; railroad yards;" etc... as well as tracts of less than 10 acres that "are completely surrounded by urban and built-up land (National Cartography and Geospatial Center 1998)."




4. Other: Defined here as total nonfederal land minus the area in categories 1-3 above.

4.1.2 Driving Variables

Population and Personal Income. Historical data were taken from the U.S. Census and arrayed at the county level. Forecasts of population and personal income were the baseline projections developed for the U.S. Assessment of Possible Vulnerabilities to Climate Variability and Change (NPA Data Services, Inc. 1999).

Land Rents. Statewide annual land rent data for the period 1960 to 1994 were taken from a database compiled by the USDA Economic Research Service. Farmland rent is defined as the difference between revenues and total variable costs for both crop and pasture uses. The rents per acre per farm were adjusted for inflation by the Gross Domestic Product price deflator.

Timber Prices. Rents for forest management directly comparable to the agricultural rents described above are not available in the South. To index the relative returns to forest uses, we examined real stumpage prices for sawtimber and pulpwood from Louisiana for the period 1960-1996. These are the only consistently measured stumpage prices available in the South for this extended period. The source of the data is Louisiana severance tax records reported by Ulrich (1987) for 1950-1965 and by Howard (1999) for 1966-1996. Units are $/mbf Scribner forsawtimber and $/cord for pulpwood.