Forestland Conversion and Recent Trends

Forests cover about one-third of the United States and range from wildland forests to urban forests. These diverse ecosystems provide a variety of habitats for wildlife; help to cleanse the air and water; supply timber, fuelwood, and other harvested products; serve as places for recreation; help to mitigate the effects of global climate change; and provide other essential goods and environmental services.

Forests are vulnerable to conversion to other land uses. An increasing number of houses and other buildings in and near forests portend growing costs and complications in fire suppression and potential loss of many values derived from forests. Long-term assessment of the condition of forests and of the relationships between forest conditions and socio-economic factors is the key to defining policy questions and actions needed to sustain forest-based services.

In this synthesis, we survey recent trends, determinants, and projections of forestland conversion in the United States. Examples with more detailed treatments, supporting tables, and figures are available in Alig and others (2003, 2004) and Alig and Ahearn (2006). Forestland conversion is a persistent issue for managers and policymakers; for example, a recent position statement concerning loss of forestland by the Society of American Foresters (2004) lists ecological effects, (e.g., effects on water quality and wildlife habitat) and socio-economic effects, (e.g., expansion of the urban-forest interface, reduction of forest recreation opportunities, reduction of long-term timber production possibilities, and loss of open space) as important implications of forest loss. We examine how socio-economic drivers of land use change, such as population totals, and personal income levels have increased substantially since the Second World War and led to changes in forest ecosystem attributes. We summarize determinants of land use changes, focusing on the societal and private trade-offs of retaining land in forests. Our projections reflect population growth that spurs demand for land for developed uses at the same time that demands for some forest products and other forest benefits are increasing. Risk and policy considerations necessitate that creating effective policy in this area will require careful deliberation concerning private and social viewpoints. For example, some forest benefits (such as wildlife habitat and other ecosystem services) can most effectively be produced at scales greater than the individual private parcel scale and because market imperfections can cause some social forest benefits to be undersupplied when this is the case (Kline and others 2004a).

Five categories of significant changes affecting forest area are:

1. afforestation

2. deforestation

3. forest fragmentation

4. forest parcelization

5. increased numbers of structures, such as houses, on forest land

This analysis does not address changes in forest cover type. For an example of a national analysis on this topic, see Alig and Butler (2004). Examination of intensification of land management is illustrated by the 2001 RPA Timber Assessment (Haynes 2003).

(Table: Data bases used) lists supporting major data bases, and (Table: Example studies) lists examples of studies that have examined land base dynamics in the United States. In the United States, millions of acres of land shift uses each year (USDA NRCS 2001) reflecting billions of choices made by individuals, corporations, nongovernmental organizations, and governments. Next, we look at recent trends in those five categories of changes in the land base. Examining historical trends provides guidance for identifying key factors that are likely to influence forest land condition and associated natural resources in future years. Discussion of historical trends is a foundation for considering projected changes.