Data still are being collected for the 1997 survey, which will be released in 1999. The survey requires a large effort. About 500 data collectors amass the information. Painstaking time and care are taken in measurements, reading field reports and scrutinizing aerial photographs of specific points in the United States. Data collected include information on soil characteristics, land use, soil erosion, vegetative cover and ecological variables such as habitat diversity.
Collectors note bodies of water, streams and rivers, buildings and roads.
They chart land reverting back to wetlands and land that is being farmed. Information can be as specific as changes in the types of crops planted on a farm and the effects those crops have on the health of the soil, Thompson said. To obtain information, Thompson relies on several labs throughout the country. One such lab, which covers Iowa and Missouri, is in Ames. They began in August 1997 and plan to complete work by July 1.