Methods for Projecting Areas of Private Timberland and Forest Cover Types

Abstract

We summarize methods used to project area changes in land uses and forest cover types in the national RPA Timber Assessments over the last 20 years, since area projection modeling systems replaced expert opinion approaches. Such models reflect that key land base changes such as afforestation and deforestation are driven by quite different socioeconomic factors. The prototype area-change modeling system—the AREACHANGE projection system—was constructed in the early 1980s for the South to support a special study between periodic RPA Timber Assessments. The southern prototype involved an area-base econometric approach, which has been applied in later RPA Timber Assessments regions and revised for the South. Other econometric models were developed in the late 1980s and later decades for the Pacific Northwest, Lake States, Maine, and other regions. Timber price projections from the Timber Assessment Projection System's modeling of markets are used as inputs in the first stage of the area-change projections. Timber harvest projections from the TAMM model, as allocated to management units by the ATLAS model, along with timber management projections from the ATLAS model are used as inputs in the second stage of projecting area changes in major forest cover types. The AREACHANGE system provides the ATLAS system with projections of timberland area by region, ownership, and major forest type. The progression of area-change modeling was heavily dependent on the availability of land-use data.