Conversions of Forest Lands: Trends, Determinants, and Policy Considerations

Ralph J. Alig, Susan Stewart, David Nowak, David Wear, Susan Stein

USDA Forest Service: Pacific Northwest Research Station, North Central Research Station, Northeastern Research Station, Southern Research Station and Washington Office respectively

Socio-economic forces drive forestland conversion, which is an issue because it results in substantial changes in ecosystem attributes. Landowners face increasing opportunity costs to keep land in forests as rising values for other land uses make forest ownership and return-on-forest investment less viable. When a forest is converted to a developed use, the loss of ecosystem services is direct and immediate, with some permanent habitat loss. For example, wildlife or fish species dependent on privately owned bottomlands at certain times of the year may disappear as these private lands are developed, regardless of quality of habitat remaining on adjacent public land.

Our synthesis paper examines trends in forest land conversions, use of theory in testing hypotheses and estimating models, empirical application of models in projections of forest land base changes, and policy implications of findings.  Recent trends indicate the deforestation of more than one million U.S. acres annually.  The Southern U.S. harvests more timber than any other country and has quite active timber markets, but even there states have recently had net forest losses. North Carolina lost 5% of its timberland in a decade, mostly to urban development. The U.S. average loss was over 2,500 acres of forests daily in the 1990s. Between 1990 and 2000, urban land in the coterminous United States increased in size by an area equivalent to Vermont and New Hampshire combined. This urban growth has expanded the urban forest, often with the loss of exurban forest land, and population densities are increasing on the remaining forestland. Between 1990 and 2000, 60% of all new U.S. homes were built in the Wildland-Urban Interface, affecting risks to both landowners and fire fighters. 

Land use theory guides research investigating determinants of forestland conversion. The conceptual model posits that landowners choose to develop land when the present value of the future stream of net returns generated by the land in a developed use exceeds the present value of the land remaining in forest use.  Land markets demonstrate (via revealed behavior) what people are willing to pay to for alternative uses of land, such as for a developed use compared to  forest use. With this economic theory as a foundation, impacts of population growth and rising personal incomes can be analyzed to model relationships between forest area change and other variables. Geo-referenced data now facilitates estimation of spatial land use change models.

Empirical applications of such models project land use change impacting forestry. The U.S. population is predicted to grow from 281 million in 2000 to 403 million by 2050, a major factor in projections that more than 50 million acres of nonfederal U.S. forests could be converted to urban and other developed uses in the next 50 years. In addition, tens of millions of acres of remaining private forests are projected to have increases in housing density. The Forests on the Edge project assessed threats to water quality and other forest benefits and impacts on nearby National Forests as more houses are built in private forests, and ranked watersheds by threat from development. Implications of these trends include greater edge effects that increase the risk of fire ignition, exotic species invasion, loss of wildlife habitat, and other disturbances.

We compare alternate projections to determine their sensitivity to model type and major assumptions; to assess uncertainty; and to compare them across spatial and temporal dimensions. From this we construct a composite outlook projecting near-term and long-term threats of forestland conversion, including identification of at-risk forests.  

Policy implications and challenges include maintaining a robust suite of forest-based benefits (e.g., open space) in the face of continuing population growth.  We discuss use of research-based findings to inform policy deliberations regarding risk mitigation alternatives pertaining to land use and forest benefits. Risk management involves intersectoral considerations; forestry is one of many possible land uses. Drivers of change such as urbanization affect many measures of resource condition, as examined in Renewable Resources Planning Act Assessments. Solutions to address conversions of forest land must be multi-faceted and should include improved valuation of forest-based environmental services. Land values provide important signals to land managers, and can be enhanced by wise management and by emerging markets for services such as carbon sequestration. Improving awareness and understanding of land values and their key role in the land conversion process is a goal of this research.

Tuesday Morning Plenary

corresponding author:

Ralph Alig
USDA Forest Service
Pacific Northwest Research Station
3200 SW Jefferson Way
Corvallis, OR 97331
541-750-7267
ralig@fs.fed.us