The Influence of Parametric Uncertainty on Projections of Forest Land Use, Carbon, and Markets.

This paper uses Monte Carlo methods and regression analysis to assess the role of uncertainty in yield function and land supply elasticity parameters on land use, carbon, and market outcomes in a long-term dynamic model of the global forest sector. The results suggest that parametric uncertainty has little influence on projected future timber prices and global output, but it does have important implications for regional projections of outputs. A wide range of outcomes are possible for timber outputs, depending on growth and elasticity parameters. Timber output in the U.S., for instance, could change by -67 to +98 million m3 per year by 2060. Despite uncertainty in the parameters, our analysis suggests that the temperate zone may sequester +30 to +79 Pg C by 2060 and +58 to +114 Pg C by 2090 while the tropics are projected to store -35 to +70 Pg C and -33 to +73 Pg C for the same time periods, respectively. Attributional analysis shows that uncertainty in the parameters regulating forest growth has a more important impact on projections of future carbon storage than uncertainty in the land supply elasticity parameters. Moreover, the results suggest that understanding growth parameters in regions with large current carbon stocks is most important for making future projections of carbon storage.

The implications of weather, nutrient prices, and other factors on nutrient concentrations in agricultural watersheds.

This paper examines how nutrient prices, weather, and other factors influenced P outputs in agricultural watersheds using a detailed daily dataset of water quality observations over a 40-year period. Because policies have focused differentially on soluble P through federal permitting programs for point sources and sediments through federal subsidies for conservation, we examine sediment, particulate P and soluble P separately. A novel element of this study is the inclusion of farm fertilizer and output (i.e., corn) prices, which affect agricultural sources of P in these watersheds. We do not find that sediment concentrations are influenced by P prices, but sediment has trended downward, and is seasonally lower in all months except February and March in the Maumee. In contrast, we find that soluble P concentrations are heavily influenced by P prices. They trended downward through 1995, but upwards since. While concerns about fall and winter P application have emerged, we do not find evidence that the distribution of soluble P concentrations shifted towards winter over time. Weather accounts for about 50% of the higher soluble P loadings in 1996-2011, but higher P prices in 2005-2011 lowered P concentrations relative to what they would have been. Other factors account for the remaining 50% of the increase in soluble P concentrations in 1996-2011.

Cumulative global forest carbon implications of regional bioenergy expansion policies.

Several previous studies have evaluated the potential greenhouse gas (GHG) benefits of forest biomass energy relative to fossil fuel equivalents over different spatial scales and time frames and applying a variety of methodologies. This paper contributes to this literature through an analysis of multiple projected sources of biomass demand growth in different regions of the world using a detailed intertemporal optimization model of the global forest sector. Given the range of current policies incentivizing bioenergy expansion globally, evaluating the combined global implications of regional bioenergy expansion efforts is critical for understanding the extent to which renewable energy supplied from forest biomass can contribute to various policy goals (including GHG emissions mitigation). Unlike previous studies that have been more regionally focused, this study provides a global perspective, illustrating how large potential demand increases for forest biomass in one or multiple regions can alter future forest management trends, markets, and forest carbon sequestration in key timber supply regions. Results show that potential near term (2015-2030) biomass demand growth in the U.S., Europe, and elsewhere can drive forest resource investment at the intensive and extensive margins, resulting in a net increase in forest carbon stocks for most regions of the world. When the reallocation of biomass away from traditional pulp and sawtimber markets is accounted for, net forest carbon sequestration increases (that stored on the land and in wood products) by 9.4 billion tons CO2 over the near term and 15.4 billion tons CO2 by 2095. Even if most of the increased forest biomass demand arises from one region (e.g., Europe) due to a particularly strong promotion of forest bioenergy expansion, changes in forest management globally in anticipation of this demand increase could result in carbon beneficial outcomes that can be shared by most regions.