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Most of the frontier forests in Asia are endangered today by rapid population growth, ever-increasing demand for agricultural land, poverty, poor institutional capacity, and lack of effective community participation in forestry activities (Mackenzie et al., 1998). Climate change is expected to affect the boundaries of forest types and areas, primary productivity, species populations and migration, the occurrence of pests and diseases, and forest regeneration. The increase in GHGs also affects species composition and the structure of ecosystems because the environment limits the types of organisms that can thrive and the amount of plant tissues that can be sustained (Melillo et al., 1996). Compositional and structural changes, in turn, affect ecosystem function (Schulze, 1994). The interaction between elevated CO2 and climate change plays an important role in the overall response of net primary productivity to climate change at elevated CO2 (Xiao et al., 1998).
Climate change will have a profound effect on the future distribution, productivity, and health of forests throughout Asia (see also Section 5.6). Because warming is expected to be particularly large at high latitudes, climate change could have substantial impact on boreal forests (Dixon et al., 1996; IPCC, 1996; Krankina, 1997). Global warming will decrease permafrost areas, improve growing conditions, and decrease areas of disturbed stands and ecosystems in a general sense, although impacts would be significantly different at various locations within the boreal forests. Moreover, forest fire is expected to occur more frequently in boreal Asia as a result of increased mean temperature (Valendik, 1996; Lelyakin et al., 1997). Pest activity also could increase with a rise in temperature, depending on the age composition of the boreal forests (Alfiorov et al., 1998).
Asia's temperate forests are a globally important resource because of their high degree of endemism, biological diversity, ecological stability, and production potential. About 150 Mha of forests in central China have been cleared during the past several decades. Efforts are now underway to at least partially restore the area under forest cover in China through reforestation, soil recovery, and water conservation programs (Zhang et al., 1997). Studies on projected impacts of climate change suggest that northeast China may be deprived of the conifer forests and its habitat, and broad-leaved forests in east China may shift northward by approximately 3° of latitude. These results are based on a 2°C increase in annual mean temperature and a 20% increase in annual precipitation (Omasa et al., 1996; Tsunekawa et al., 1996).
Tropical moist forests have trees with higher densities of wood and larger proportions of branch wood relative to those in temperate forests. As many as 16 countries of tropical Asia are located within the humid tropical forest region. These forests and woodlands are important resources that must be safeguarded, given the heavy use of wood as fuel in some countries. Past policies in the humid tropics have focused mainly on natural forest protection and conservation (Skole et al., 1998). However, there is a need to shift emphasis from conservation alone to a strategy that involves sustained development, investment performance, and public accountability (see Section 5.6). Encouragingly, the current annual rate of reforestation is highest in tropical Asia as a result of relatively high investments in reforestation schemes, including social forestry.
Most semi-arid lands in Asia are classified as rangelands, with a cover of grassland or scrublands. Although the share of land area used for agricultural purposes is about 82% of the total area, it is mainly low-productive pastures. With an increase in temperature of 2-3°C combined with reduced precipitation as projected for the future in the semi-arid and arid regions of Asia, grassland productivity is expected to decrease by as much as 40-90% (Smith et al., 1996). Approximately 70% of pastures are facing degradation, with dramatic decreases in fodder yield over recent decades in some parts of Mongolia (Khuldorj et al., 1998). Rangelands in Nepal also have been subject to degradation in recent years (NBAP, 2000). Climate change is likely to represent an additional stress to rapid social change in many of Asia's rangelands.
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