About the Data

Estimates presented here are based upon the latest information from the National Resources Inventory (NRI). The NRI is a longitudinal sample survey based upon scientific statistical principles and procedures. It is conducted by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS), in cooperation with Iowa State University’s Center for Survey Statistics and Methodology.

The results are the first available from the new Annual NRI. Previously, NRI data were collected at 800,000 sample sites every 5 years. Now the data are collected every year, but for slightly less than 25 percent of these same sample sites. The 2001 data are suitable only for analysis at a national scale because of this reduced sample size. As additional data are collected each year, results will become available for regional, state, and sub-state analysis. Current estimates cover the contiguous 48 states. Future estimates will also cover Hawaii, Alaska, the Caribbean, and selected Pacific Basin islands.

The findings on Urbanization and Development come from the NRI data category “Land Cover/Use” which comprises mutually exclusive categories such as cropland, pastureland, rangeland, forest land, other rural land, developed land, and water areas. The NRI uses this classification to account for each and every acre of nonfederal land within the Nation. Every parcel of land is described by one and only one of these categories.

Developed Land contains three Land Cover/use categories:

1. Large Urban & Built-up Areas (greater than 10 acres in size);
2. Small built-up Areas (less than 10 acres in size);
3. Rural Transportation Land (roads, railroads, and associated rights-of-way).

For the NRI, Developed Land areas are considered (permanently) removed from the rural land base. Other agencies and groups that collect seemingly similar data have different reasons for collecting data. This means that these other sources of data will show differences and similarities with NRI data. Thorough examination and analysis of the data from two differing sources can be beneficial and strengthen understanding of the issues.

The NRI approach to conducting inventories facilitates examining trends in rural and developed land uses over time because –

• the same data have been collected since 1982 [definitions and protocols have remained the same],
• the inventory accounts for 100 percent of the surface area,
• quality assurance and statistical procedures are designed to ensure that trend data are scientifically legitimate and unambiguous, and
• it is easy to track lands as they go from one land-use category to another.

Irrespective of the scale of analysis, margins of error must be considered. Margins of error are presented for all NRI estimates.