Forests constitute both a sink and a source of atmospheric CO2. Forests absorb carbon through photosynthesis, but emit carbon through decomposition and when trees are burned due to anthropogenic and natural causes. Managing forests in order to retain and increase their stored carbon will help to reduce the rate of increase in atmospheric CO2 and stabilize atmospheric concentrations. Even though some degraded lands are unsuitable for forestry, there is considerable potential for mitigation through improved management of forest lands for carbon conservation, storage, and substitution, in balance with other objectives. This section describes national forest practices and measures and international projects and programs that may be successfully pursued to achieve this goal.20
Forests currently cover about 3.4 Gha world-wide, with 52% of the forests in the low latitudes (approximately 0-25°N and°S latitude), 30% in the high latitudes (approximately 50-75°N and°S latitude), and 18% in the mid-latitudes (approximately 25-50°N and°S latitude) (SAR II, 24.2.1). The world's forests store large quantities of carbon, with an estimated 330 Gt C in live and dead above- and below-ground vegetation, and 660 Gt C in soil (mineral soil plus organic horizon) (SAR II, 24.2.2). An unknown quantity of carbon also is stored in products such as wood products, buildings, furniture, and paper.
High- and mid-latitude forests are currently estimated to be a net carbon sink of about 0.7 ± 0.2 Gt C/yr. Low-latitude forests are estimated to be a net carbon source of 1.6 ± 0.4 Gt C/yr, caused mostly by clearing and degradation of forests (SAR II, 24.2.2). These sinks and sources may be compared with the carbon release from fossil fuel combustion, which was estimated to be 6 Gt C in 1990.
7.2 Technologies for Reducing GHG Emissions in the Forest Sector
Forest management practices that can restrain the rate of increase in atmospheric CO2 can be grouped into three categories: (i) Management for carbon conservation; (ii) management for carbon sequestration and storage; and (iii) management for carbon substitution. Conservation  practices include options such as controlling deforestation, protecting forests in reserves, changing harvesting regimes, and controlling other anthropogenic disturbances, such as fire and pest outbreaks. Sequestration and storage  practices include expanding forest ecosystems by increasing the area and/or biomass and soil carbon density of natural and plantation forests, and increasing storage in durable wood products. Substitution  practices aim at increasing the transfer of forest biomass carbon into products rather than using fossil fuel-based energy and products, cement-based products, and other non-wood building materials.
The potential land area available for the implementation of forest management options for carbon conservation and sequestration is a function of the technical suitability of the land to grow trees and the actual availability as constrained by socio-economic circumstances. The literature reviewed for the SAR (SAR II, 126.96.36.199) suggests that globally 700 Mha of land might be available for carbon conservation and sequestration (345 Mha for plantations and forestry, 138 Mha for slowed tropical deforestation, and 217 Mha for natural and assisted regeneration). Table 14 provides an estimate of global potential to conserve and sequester carbon, based on the above studies. The tropics have the potential to conserve and sequester the largest quantity of carbon (80% of the total potential), followed by the temperate (17%), and the boreal zones (3%). Natural and assisted regeneration and slowing deforestation account for more than half of the amount in the tropics. Forestation and agroforestry contribute the remaining tropical sink, and without these efforts regeneration and slowing deforestation would be highly unlikely.
Scenarios show that annual rates of carbon conservation and sequestration from all of the practices mentioned increase over time (SAR II, 188.8.131.52). Carbon savings from slowed deforestation and regeneration initially are the highest, but from 2020 onwards plantations sequester practically identical amounts as they reach maximum carbon accretion (see Figure 3). On a global scale, forests turn from a global source to a sink by about 2010, as tropical deforestation is offset by carbon conserved and sequestered in all zones.
Using the mean cost of establishment or first costs for individual options by latitudinal region, the cumulative cost (undiscounted) for conserving and sequestering the quantity of carbon shown in Table 14 ranges from about $250-300 billion at an average unit cost ranging from $3.7-4.6/t C (SAR II, 24.5.4). Average unit cost decreases with more carbon conserved by slowing deforestation and assisting regeneration, as these are the lowest cost options. Assuming an annual discount rate of 3%, these costs fall to $77-99 billion and the average unit cost falls to $1.2-1.4/t C. Land costs and the costs of establishing infrastructure, protective fencing, education, and training are not included in these cost estimates.
While the uncertainty in the above estimates is likely to be high, the trends across options and latitudes appear to be sound. The factors causing uncertainty are the estimated land availability for forestation projects and regeneration programs, the rate at which tropical deforestation can actually be reduced, and the amount of carbon that can be conserved and sequestered in tropical forests. In summary, policies aimed at promoting mitigation efforts in the tropical zone are likely to have the largest payoff, given the significant potential for carbon conservation and sequestration in tropical forests. Those aimed at forestation in the temperate zone also will be important.
7.3 Measures for Reducing GHG Emissions in the Forest Sector
Forest management practices with the largest potential for carbon conservation and sequestration range (in declining order of importance) from slowing deforestation and assisting regeneration in the tropics to forestation schemes and agroforestry in tropical and temperate zones (Table 14). To the extent that forestation schemes yield wood that can substitute for fossil fuel-based material and energy, their carbon benefit will be multiplied. The following subsections examine the measures relevant to the implementation of each type of practice.
7.3.1 Slowing Deforestation and Assisting Regeneration
The causes of deforestation range from clearing of forest land for agriculture, mineral extraction, and hydro-reservoirs to degradation of forests for fuel wood. Land cleared for agriculture may eventually lose its fertility and become suitable only as rangeland. Socio-economic and political pressures, often brought about by the needs of growing populations living in marginal areas at subsistence levels, are principal factors causing deforestation in much of the tropics (SAR II, 184.108.40.206). In Brazil, on the other hand, wealthier investors are major agents of deforestation, clearing land for cattle ranches that often derive part of their financial attractiveness from land speculation.
Both forest-related and non-forest measures and policies have contributed to deforestation. These include short-duration contracts that specify annually harvested amounts and poor harvesting methods, which encourage contractors to log without considering the concession's sustainability. Royalty structures that provide the government with too little revenue to permit reforestation adequate for arresting forest degradation after harvesting also lead to deforestation. Non-forest policies that lead to direct physical intrusion of natural forests are another prime cause of deforestation. These include land tenure policies that assign property rights to private individuals on the basis of "improvement" through deforestation, settlement programs, investments promoting dams and mining, and tax credits or deductions for cattle ranching.
Table 15 shows the measures whose successful implementation would slow deforestation and assist regeneration of biomass. Each of these measures will conserve biomass, which is likely to have a high carbon density, and will maintain or improve the current biodiversity, soil, and watershed benefits. The capital costs of these measures are low, except in the case of recycled wood, where the capital cost depends on the product being recycled. The first two measures are likely to reduce sectoral (agricultural) employment as deforestation is curtailed. If the subsidies are gainfully invested, they have the potential to create jobs elsewhere in the economy to offset this loss. Sustainable forest management has the potential to create economic activity and employment on a long-term basis. The implementation of forest conservation legislation requires strong political support and may incur a high administrative burden. Removing subsidies may run into strong opposition from vested interests. Jointly implemented projects have been slow to take off as the perceived transaction costs are high and financing is difficult to obtain when carbon sequestration is the main benefit. Although sustainable forest management is politically attractive, its implementation requires local participation, the establishment of land tenure and rights, addressing gender and equity issues, and the development of institutional mechanisms to value scarcity; the combination of these factors may incur high administrative costs.
Although reducing deforestation rates in the tropics may appear to be difficult, the potential for significant reduction is high, and there are countries, such as Brazil, India, and Thailand, where governments have adopted explicit measures and policies to halt further deforestation (SAR II, 220.127.116.11). For instance, in June 1991, the Brazilian government issued a decree (No. 151) suspending the granting of fiscal incentives to new ranching projects in Amazonian forest areas in order to further decrease the annual rate of deforestation (which, as a consequence of economic recession, had reduced to 1.1 Mha for 1990-91 from 2 Mha/yr during 1978-88). The long-term impact of this decree is not yet known, but additional measures could be applied if necessary.
In addition to national measures, protection projects supported by foreign governments, non-government organizations, and private companies are being formed to arrest deforestation and conserve and/or sequester carbon. The Rio Bravo Preservation and Forest Management Project in Belize, which has been approved under the U.S. Initiative on Joint Implementation (US IJI), will purchase a 6,000 ha parcel of endangered forest land to protect two adjacent tracts from conversion to farmland, and is estimated to sequester 3 Mt C. The project participants include Wisconsin Electric Power Company, The Nature Conservancy, Programme for Belize, Detroit Edison Company, Citienergy, and PacfiCorp. The ECOLAND Project will preserve tropical forest through purchase of 2,000-3,000 ha in the Esquinas National Park, which is under threat of deforestation in southwestern Costa Rica. The project partners include U.S., Costa Rican, and Austrian institutions.
Sustaining the programs, projects, and measures that are being implemented to slow deforestation will pose many challenges. In India, declining rural population growth rates have helped policymakers sustain the slowed deforestation rate. Elsewhere, however, the fundamental challenge will be to continue to find an alternative livelihood for forest dwellers or deforesters, which may require integrating dwellers into the urban social fabric of a nation. Deforesters may be drawn to the forest for reasons other than land cultivation, and policymakers need to resort to largely non-forest policies in such situations. Another challenge in the protection of forests and national parks is to increase government budgets allocated for this purpose, which often are inadequate to provide enough forest rangers, and fencing and other infrastructure to halt land encroachment.
Forestation means increasing the amount of carbon stored in vegetation (living above- and below-ground), dead organic matter, and medium- and long- term wood products. This process consists of reforestation, which means replanting trees in areas that were recently deforested (less than 50 years), and afforestation, which means planting trees on areas which have been without forest cover for a long time (for over 50 years). In temperate regions, reforestation rates tend to be high: Canadian reforestation during the 1980s was reported to be 720,000 ha/yr (SAR II, 24.4.1) and U.S. rates have averaged 1 Mha/yr between 1990 and 1995. There are significant afforestation efforts in both tropical and temperate countries. China alone boasts of having planted 30.7 Mha between 1949 and 1990, while India had 17.1 Mha planted by 1989 (SAR II, 24.4). The United States had 5 Mha of forest plantations by 1985, while France has more than doubled its forest area since the beginning of the last century, from 7 to 15 Mha; by 1994, New Zealand was managing 1.4 Mha of planted forest on sustained yield principles.
Measures for forestation and agroforestry include (i) government investment programs targeted towards these practices on government-owned land; (ii) community forestry programs that may be supported by government extension services; and (iii) private plantations with financial and other incentives provided by the government (see Table 16). These measures may be targeted towards production forests, agroforestry, and conservation forests. Conservation forests include those managed for soil erosion and watershed management. Those managed primarily for carbon sequestration would have to be located on lands with low opportunity costs, or else they would be likely to be encroached upon for other uses. Government subsidies may take the form of taxation arrangements that do not discriminate against forestry, tax relief for projects that meet specific objectives, and easy access to bank financing at lower-than-market interest rates.
Government subsidies have been important for initiating and sustaining private plantations. Since World War II, 3.15 Mha have been afforested in France, and the 1995 French National Programme for the mitigation of climate change calls for an afforestation rate of 30,000 ha/yr from 1998 onward, which will sequester 79-89 Mt C over 50 years at a cost of $70/t C. An interesting development in India in the last few years has been the planting of teak (Tectona grandis  ) by private entrepreneurs, with capital raised in private capital markets (SAR II, 15.3.3). This program, while occupying only a few thousand ha at present, has the potential to expand to 4-6 Mha of India's 66 Mha of degraded lands. The teak may be used in buildings and furniture.
In addition to national programs, other programs are being initiated and supported in some countries by foreign governments, non-governmental organizations, and private companies. One example is RUSAFOR, which is a US IJI-approved afforestation project in the Saratov region of Russia (SAR II, Box 24-2). The project proposes to plant seedlings on 500 ha of marginal agricultural land or burned forest stands. Initial seedling survival rate is 65%. The project will serve as an example for managing a Russian forest plantation as a carbon sink. Another example is the Reduced-Impact Logging Project, for which funds were provided by New England Power Company (SAR II, Box 24-2). This project aims to reduce by half the damage to residual trees and soil during timber harvesting, thus producing less woody debris, decomposition, and release of carbon.
For government forestation and agroforestry policies to succeed, the formulation of a coordinated land-use strategy, agreed-upon land tenure rights that are unambiguous and not open to legal challenges, and markets developed enough to ensure a sustained demand for forest products will be essential.
7.3.3 Substitution Management
Substitution management has the greatest mitigation potential in the long term. It views forests as renewable resources, and focuses on the transfer of biomass carbon into products that substitute for—or reduce the use of—fossil fuels, rather than on increasing the carbon pool itself. Growing trees explicitly for energy purposes has been attempted with mixed success in Brazil, the Philippines, Ethiopia, Sweden, and other countries, but the potential for bioenergy is very large (see Section 5.2.5 for estimates of bioenergy supply potential).
Over time, the displacement of fossil fuels for low energy-intensive wood products is likely to be more effective in reducing carbon emissions than sequestering carbon in plantations on deforested and otherwise degraded lands in developing countries, and on excess cropland in OECD Annex I countries. For example, substituting plantation wood for coal in the generation of electricity can avoid carbon emissions by an amount up to four times the carbon sequestered in the plantation (see Table 17) (SAR II, 24.3.3). The generation of biofuels and bioelectricity is far more complex, since commercialization is not easy and energy pricing and marketing barriers are yet to be overcome. Town and village biomass energy systems have the advantage of providing employment, reclaiming degraded land, and providing associated benefits to rural areas. Central heating systems could be converted to biomass-based ones to supply heat and electricity in colder climates.
In non-Annex I countries, the use of electricity in rural areas is low. In many countries, such as in sub-Saharan Africa, less than 5% of villages are electrified; in countries such as India, even though over 80% of rural settlements are electrified, less than a third of rural households have electricity. Appropriate government policies are needed that will (i) permit small-scale independent power producers to generate and distribute biomass electricity; (ii) transfer technologies within the country or from outside; (iii) set a remunerative price for electricity; and (iv) remove restrictions on the growing, harvesting, transportation, and processing of wood (except possibly restrictions on conversion of good agricultural land to an energy forest) (SAR II, 24.3.3).
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