10.4.4 Natural ecosystems and biodiversity

10.4.4.1 Structure, production and function of forests

Up to 50% of the Asia’s total biodiversity is at risk due to climate change. Boreal forests in North Asia would move further north. A projected large increase in taiga is likely to displace tundra, while the northward movement of the tundra will in turn decrease polar deserts (see Chapter 15, Section 15.2.2, Figure 15.3; Callaghan et al., 2005; Juday et al., 2005). Large populations of many other species could also be extirpated as a result of the synergistic effects of climate change and habitat fragmentation (Ishigami et al., 2003, 2005). Projections under doubled-CO₂ climate using two GCMs show that 105 to 1,522 plant species and 5 to 77 vertebrates in China and 133 to 2,835 plants and 10 to 213 vertebrates in Indo-Burma could become extinct (Malcolm et al., 2006).

As a consequence of climate change, no significant change in spatial patterns of productivity of the forest ecosystems in North-East China is projected (Liu et al., 1998). The areal coverage of broad-leaved Korean pine forests is projected to decrease by 20 to 35% with a significant northward shift (Wu, 2003). About 90% of the suitable habitat for a dominant forest species, beech tree (Fagus crenata), in Japan could disappear by the end of this century (Matsui et al., 2004a, b). The impact of elevated atmospheric CO₂ on plant biomass production is influenced by the availability of soil nitrogen and deposition of atmospheric nitrogen (Oren et al., 2001; Hajima et al., 2005; Kitao et al., 2005; Reich et al., 2006). The overall impact of climate change on the forest ecosystems of Pakistan could be negative (Siddiqui et al., 1999).

The observations in the past 20 years show that the increasing intensity and spread of forest fires in North and South-East Asia were largely related to rises in temperature and declines in precipitation in combination with increasing intensity of land uses (see Section 10.2.4.4). Whether this trend will persist in the future or not is difficult to ascertain in view of the limited literature on how the frequency and severity of forest and brush fires will likely respond to expected increase in temperature and precipitation in North and South-East Asia (see Section 10.3.1). The uncertainty lies on whether the expected increase in temperature would be enough to trigger more frequent and severe fires despite the projected increase in precipitation. One study on the impacts of climate change on fires show that for an average temperature increase of 1°C, the duration of wild fire season in North Asia could increase by 30% (Vorobyov, 2004), which could have varying adverse and beneficial impacts on biodiversity, forest structure and composition, outbreaks of pest and diseases, wildlife habitat quality and other key forest ecosystem functions.