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This section addresses potential associated impacts on various socioeconomic dimensions of sustainable development, including provision of wood products and biofuels; agriculture; rural poverty alleviation; and aesthetic, spiritual, and recreational values.
The world's forests produced about 3.2 billion m3 of harvested roundwood in 1994 and are projected to produce almost 3.7 billion m3 per year by 2010 (FAO, 1997b). Of the 1994 total, about 1.7 billion m3 (53 percent) was used as fuelwood and the remainder as industrial roundwood (e.g., sawlogs and pulpwood). Approximately half of the fuelwood was produced (and consumed) in Asia, one-quarter in Africa, and one-eighth in South America. World industrial roundwood production was concentrated in North America (40 percent), Europe (19 percent), Asia (18 percent), and the countries of the former Soviet Union (8 percent).
At the global level, forestry was estimated to account for 2 percent of the world's gross domestic product (GDP) and 3 percent of international trade. The estimated value of wood consumption in 1994 was more than US$400 billion, with industrial usage accounting for 75 percent. Several countries are using forest products as their main foreign exchange earners; any change in the status of forests in these economies is likely to affect their foreign trade and debt status (FAO, 1999). Globally, wood is expected to become increasingly scarce by 2050, assuming constant per capita wood use and a 2 percent annual volume growth increment (Solomon et al., 1996). The greatest shortfall will be in the tropics because of the projected increase in population that drives the conversion of forest to agricultural land (Zuidema et al., 1994). There probably will be an associated shortage of fuelwood.
Aggregate temperate zone timber needs are likely to be met over the foreseeable future, given current projections of timber supply and demand (see, for instance, projections for the United States by Haynes et al., 1995). Trends in the boreal zone are less certain; they depend on the forest response to climate change. Climatic changes could lead to increased growth-if anticipated warmer conditions allow increase growth-or reduced timber production, if increasing incidences of pests, diseases, or fire were to increase tree mortality (Kirschbaum et al., 1996; Solomon et al., 1996).
Future changes in climate may affect forest productivity in ways that change the level and distribution of global timber supply. Perez-Garcia et al. (1997) modeled the effect of alternative climate scenarios on global timber markets and found, in general, that the expected rise in net primary productivity (NPP) would slightly expand timber supply and reduce timber prices. The net welfare effects varied across forest-product consumers and producers, as well as by region. Some Parties would benefit from enhanced timber stocks (e.g., consumers and timber importing countries), whereas some stand to lose (producers and timber exporting countries). Climatic changes projected by current climatological and ecological models may have relatively small effects on timber markets (Burton et al., 1997), but these effects can be quite sensitive to the climatological and ecological model used for selection and the extent to which species migration is captured (Sohngen and Mendelsohn, 1998; McNulty et al., 1999). These studies do not estimate the effects of climate change on non-timber and non-market outputs and therefore do not capture potential effects on biodiversity, watersheds, and other forest outputs. Moreover, possible climate change and associated impacts should be viewed within the context of many other activities and policies occurring in different sectors and possible mitigation responses by humans.
Stand-level analyses have shown that paying landowners to store carbon-although it still allows them to harvest timber-can elongate timber rotations significantly if carbon is priced sufficiently high (van Kooten et al., 1995; Hoen and Solberg, 1997), though the rotation age response has been found to be lower for commercial plantations than for natural forests in the United States (Murray, 1999). Longer rotations often co-produce environmental benefits, such as improved habitat for fauna, but collectively may lead to temporary constraints on aggregate timber supply until forests are fully regulated at longer rotation levels. Longer rotations and resultant production of larger logs could also result in more valuable timber. If forest carbon reserves are created, wherein no harvesting activity occurs, the corresponding supply constraint is permanent. Changes in timber availability directly affect forest industry employment but must also be viewed in the context of other factors that affect forest-based employment, such as capital-labor substitution and other forms of technical change.
Establishment of more forests also provides the opportunity to use that wood as a biofuel (Nakicenovic et al., 1996). In some circumstances, forest establishment could also decrease deforestation and degradation for fuelwood. Greater use of biofuel could also have the advantages of fossil fuel substitution by reducing the use of coal, kerosene, liquified petroleum gas (LPG), and so forth. Under steady-state conditions, the amount of carbon released through combustion of biofuels is offset by the amount of carbon taken up in biomass.
Establishment of plantations to produce charcoal is one prominent form of biofuel production. Plantations for charcoal may have substantial carbon advantages over traditional pulpwood plantations because of their ability to substitute for fossil fuels (Fearnside, 1995; Schlamadinger and Marland, 1996; Marland et al., 1997). Tree plantations can have mixed effects on the environment, depending on the characteristics of the land and the land cover being replaced by the plantation, as well as indirect socioeconomic effects through market processes. Although the use of biofuels in energy production is highly desirable from a carbon management point of view, it may not be without its own social and environmental side effects on air quality and waste disposal (Sutton, 1994; Fearnside, 1999d).
Savings in the emission of GHGs can also be achieved through material substitution. Typical building materials-such as steel, plastics and aluminum-have large energy requirements for mining, processing, smelting, and, with some materials, reduction of oxidized ore. These energy requirements lead to corresponding CO2 emissions. Cement production also leads to additional direct CO2 release during manufacturing. Wood leads to the lowest emissions because it requires only minor energy inputs in harvesting and sawing. Hence, any substitution of wood for other materials could reduce energy requirements and associated GHG emissions (Kirschbaum, 2000). Moreover, the production of metals and plastics generates higher volumes of air, water, and solid waste pollutants than wood products such as lumber-particularly so with toxic chemicals (USEPA, 1997).
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