Land use can be a critical factor in climate change and greenhouse gas production. The primary source of the increased atmospheric concentration of carbon dioxide since the preindustrial period results from fossil fuel use, with land-use change providing another significant contribution (IPCC 2007). Forest and agricultural land uses influence the global carbon cycle; forest growth and agricultural productivity are in turn influenced by global climate change. Climate change may alter the productivity of forests, altering forest resource management, processes of adaptation, and ultimately forest product harvests and forest ecosystem services both regionally and nationally.

In terms of decision support, forest owners need information about the comparative advantage of sequestering carbon and other greenhouse gases (GHG) in forest practices (e.g., afforestation) as compared to those in agriculture. Second, within the forest sector, landowners and managers need information about comparative advantages and the relative costs of land and resources on different forest ownerships to sequester greenhouse gases; they also need information about costs of adaptation for different forest ownerships. Third, managers need to understand that unintended consequences can result from intervention in markets by the government or other groups. For example, interplay in markets between adaptation activities and climate change mitigation strategies (e.g., expand use of corn-based ethanol) can have unintended effects across different land ownership groups. Fourth, feedbacks between climate change and land-use changes can be complex. Climate change is part of larger global change (Alig 2003), which includes land-use changes and other human-caused alterations in the natural environment.

Driving Forces

Human activities contribute greatly to global climate change (IPCC 2007). Decisions by people will be important in implementing adaptation to climate change and the efficiency of mitigation strategies (e.g., afforestation to help mitigate climate change). Supply, demand, and their effect on prices influence land use and the costs of adaptation and climate change mitigation. Land use may change both as people adapt and as people act to sequester more greenhouse gases by altering land uses (Alig et al. 2004). Current interest in biofuels production has resulted in greatly expanded use of corn for ethanol production. This has left less agricultural land for afforestation. One unintended consequence could be landowners converting forest land to agriculture and the loading of more agricultural fertilizers, herbicides, and other pollutants into aquatic ecosystems (McCarl and Schneider 2001).

Climate change may also affect the production of forest and agricultural products. The National Climate Change Assessment in the late 1990s (Irland et al. 2001) found that net economic impacts of climate change across forestry and agriculture were positive but relatively small (Alig et al. 2002); further, producers and consumers could be affected differently. Where climate change was projected to induce yield increases in production, consumers were found to benefit because a greater supply led to lower prices. Projections of yield decreases had the opposite effect; producers benefited because less quantity supplied led to higher prices.

Options for Management

Forest-based efforts to sequester greenhouse gases could serve as a bridge to a broader implementation of substantial greenhouse emission reductions (Alig et al. 2005). Adaptation and mitigation activities will interact in ways that are difficult to predict; much policy discussion has yet to be translated to on-the-ground activities. Decision support can be aided by analyzing "what if" scenarios, such as possible gains from reducing deforestation in the United States and other countries. Adaptation in the forest and agricultural sectors could also limit effects of climate change (Alig et al. 2004). Producers could change both the types of management that they practice (planting, thinning, etc.) and the ages at which they harvest trees, depending on the type of owner (private or public).

Other options for adaptation and mitigation include land market adjustments, interregional migration of production (e.g., northerly migration of production capacity), substitution in consumption between wood and nonwood products (reflected in overall growth in wood products use), and between sawtimber and pulpwood (Alig et al. 2004). For example, growing forest stands to older ages and larger sizes where sawtimber is produced would allow for use of the timber products in longer-lived final products (e.g., wooden beams) as compared to paper products produced using smaller pulpwood-size trees. Consumers could shift their patterns of consumption between forest and nonforest products. For example, life cycle analysis has shown that use of wood products can reduce the emissions of greenhouse gases associated with house construction, as contrasted to use of nonwood building materials such as steel, concrete, and bricks.

Not all mitigation actions are created equal in terms of their ability to reduce GHG emission, nor is the potential for action and impact the same for major forest ownerships. Policies that favor one set of actions and ownership over the other may have unintended consequences (Alig et al. 1997). The PNW Station scientists and cooperators have developed a model called FASOM GHG to help evaluate the interplay of land use policy, alternative fuels, and the agricultural and forestry sectors (Alig et al. 2002). The FASOM GHG model projects future changes for land use; investment in forest management; harvest and regeneration; greenhouse storage in forest ecosystems, wood products, and agricultural soils and crops; effects of carbon prices on forest and agricultural land use and management; effects of climate change on the economics of forest and agricultural production; and biofuels production from forestry and agriculture. On the forestry side, this includes both private and public forest lands, and the model can also estimate adaptation options and costs of such adaptation to climate change. Both forest and agricultural land store carbon, although forests typically store more and for a longer period. Additionally forests don't need to be harvested and replanted each year with machinery that runs on fuel.

Slowing down deforestation is a critical step to mitigating climate change. Over a recent 15-year period, we lost an amount of U.S. forest land equivalent to forest area in the state of Washington (Alig et al. 2008). Although forest areas have increased in some regions, we lose all sizes of trees through deforestation, whereas we gain only very small trees initially through afforestation, so that an acre lost is not the same as an acre gained. Afforestation (the planting of trees in an area where there weren't any, such as on former agricultural land) and subsequent tree growth is one method for increasing the globe's carbon storage capacity.

Working with private forest landowners is essential because most timber is harvested from private land. Timber harvests on National Forest System land account for only 2 percent of the Nation's timber harvest (Adams and Haynes 2007). The length of the harvest rotation can affect both the amount of carbon that is sequestered, because older forests store more carbon than younger ones, and the supply of wood products in the market. Valuing the ecosystem service of carbon sequestration in the marketplace is another aspect of mitigation and could create incentive for private forest owners to maintain or increase their forested acreage.

Agricultural subsidies also influence land use. For example, the current emphasis on biofuels has led to an increase in subsidized corn production for ethanol, leaving less land available for afforestation. Unintended consequences from an emphasis on corn-based ethanol as an alternative to oil include conversion of forest land to agriculture and an increase in the use of pesticide, herbicides, and fertilizers that could negatively impact aquatic ecosystems as well as increased soil erosion and forest fragmentation and reduced wildlife habitat.

The U.S. South has a lot of private land suitable for either forestry or agriculture. When crop land is converted to forest land, it doesn't have to be a monoculture. Multiple tree species (and agroforestry combinations) could be planted so that the converted land would provide multiple benefits. We could do this in a clever way. Afforestation can help combat not just climate change but fragmentation and improve wildlife habitat and water quality (Alig 2008).

Mitigation options also include using wood instead of nonwood products (Alig et al. 2004). Life cycle analyses have shown that GHG emissions associated with housing construction are lower than if building materials such as steel, concrete, and bricks are used. Another mitigation strategy is to manage forest stands for sawtimber rather than pulpwood. Sawtimber comes from larger, older trees that sequester more carbon, and the final product, such as wood beams tends to have a longer shelf life than products from smaller pulpwood-size trees that may go largely for paper products.

Addressing global climate change requires broader viewpoints than typically employed in the past, both in terms of spatial and temporal scales. The lens through which we view transformations of the environment changes from generation to generation. Increasingly, we as society recognize the impacts of human activities. People have far-reaching effects on our environment, and human-nature interactions have grown more complex. Science to support policy actions has expanded but still contains many gaps regarding global change. For example, difficulties remain in reliably simulating and attributing observed temperature changes at smaller scales (IPCC 2007). On these relatively small scales, natural climate variability is relatively larger, making it harder to distinguish changes expected owing external forcings. Thus, natural resource management and policy formulation should be developed with such limitations in mind.

Valuing carbon sequestration in the marketplace

To help decisionmakers understand the carbon implications of potential changes in public timberland management, we compared a baseline timber harvest scenario at a large scale with two alternative harvest scenarios. We estimated annual carbon stock changes associated with each scenario. A "no timber harvest" scenario eliminating harvests on U.S. public timberlands could result in an annual increase of as much as 43 percent over current sequestration levels on public timberlands and would offset up to 1.5 percent of total U.S. greenhouse gas (GHG) emissions. In contrast, moving to a more intense harvesting policy similar to that which prevailed in the 1980s, may result in annual reductions of 50 to 80 percent in anticipated carbon sequestration (Depro et al. 2008).

If carbon sequestration were valued in the marketplace as part of a GHG offset program, the economic value of sequestered carbon on public lands could be substantial, relative to timber harvest revenues (Depro et al. 2008). Larger than anticipated changes in natural disturbances such as fire, insects, and disease from climate change could affect these results. Other work showed the possibility of a 10-percent increase in the seasonal severity of fire hazard over much of the United States under climate change scenarios.

Further, public and private decisions about forest carbon sequestration are linked in that society's welfare can be enhanced by considering timing of forest management across ownerships at a landscape level. Given diversity of conditions across ownerships (e.g., differences in forest age class distributions), it may be possible to achieve a given carbon sequestration target at lower social cost at landscape scales. This would depend on the timing of timber harvest and silvicultural activities, and on them being jointly considered across private and public timberlands.

Useful Links

The Forestry and Agriculture Greenhouse Gas Modeling Forum Web site: http://foragforum.rti.org.

Land Use and Land Cover Dynamics: http://www.fsl.orst.edu/lulcd/

Recommended Citation

Alig, Ralph. 2008. Policy Analyses and Climate Change. (May 28, 2008). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. http://www.fs.fed.us/ccrc/topics/policy-analyses.shtml

Policy Analyses and Climate Change

Issue

Driving Forces

Options for Management

Valuing carbon sequestration in the marketplace

Recommended Reading

Useful Links

Recommended Citation