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IPCC Fourth Assessment Report: Climate Change 2007 |
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Climate Change 2007: Working Group III: Mitigation of Climate Change 9.2 Status of the sector and trends 9.2.1 Forest area The global forest cover is 3952 million ha (Table 9.1), which is about 30 percent of the world’s land area (FAO, 2006a). Most relevant for the carbon cycle is that between 2000 and 2005, gross deforestation continued at a rate of 12.9 million ha/yr. This is mainly as a result of converting forests to agricultural land, but also due to expansion of settlements, infrastructure, and unsustainable logging practices (FAO, 2006a; MEA, 2005b). In the 1990s, gross deforestation was slightly higher, at 13.1 million ha/yr. Due to afforestation, landscape restoration and natural expansion of forests, the most recent estimate of net loss of forest is 7.3 million ha/yr. The loss is still largest in South America, Africa and Southeast Asia (Figure 9.1). This net loss was less than that of 8.9 million ha/yr in the 1990s. Table 9.1: Estimates of forest area, net changes in forest area (negative numbers indicating decrease), carbon stock in living biomass, and growing stock in 1990, 2000, and 2005 | Region | Forest area, (mill. ha) | Annual change (mill. ha/yr) | Carbon stock in living biomass (MtCO2) | Growing stock in 2005 |
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| 2005 | 1990-2000 | 2000-2005 | 1990 | 2000 | 2005 | million m3 |
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| Africa | 63,5412 | -4.4 | -4.0 | 241,267 | 228,067 | 222,933 | 64,957 | | Asia | 571,577 | -0.8 | 1.0 | 150,700 | 130,533 | 119,533 | 47,111 | | Europea) | 1001,394 | 0.9 | 0.7 | 154,000 | 158,033 | 160,967 | 107,264 | | North and Central America | 705,849 | -0.3 | -0.3 | 150,333 | 153,633 | 155,467 | 78,582 | | Oceania | 206,254 | -0.4 | -0.4 | 42,533 | 41,800 | 41,800 | 7,361 | | South America | 831,540 | -3.8 | -4.3 | 358,233 | 345,400 | 335,500 | 128,944 | | World | 3,952,026 | -8.9 | -7.3 | 1,097,067 | 1,057,467 | 1,036,200 | 434,219 |
Thus, carbon stocks in forest biomass decreased in Africa, Asia, and South America, but increased in all other regions. According to FAO (2006a), globally net carbon stocks in forest biomass decreased by about 4,000 MtCO2 annually between 1990 and 2005 (Table 9.1). The area of forest plantation was about 140 million ha in 2005 and increased by 2.8 million ha/yr between 2000 and 2005, mostly in Asia (FAO, 2006a). According to the Millennium Ecosystem Assessment (2005b) scenarios, forest area in industrialized regions will increase between 2000 and 2050 by about 60 to 230 million ha. At the same time, the forest area in the developing regions will decrease by about 200 to 490 million ha. In addition to the decreasing forest area globally, forests are severely affected by disturbances such as forest fires, pests (insects and diseases) and climatic events including drought, wind, snow, ice, and floods. All of these factors have also carbon balance implications, as discussed in Sections 9.3 and 9.4. Such disturbances affect roughly 100 million ha of forests annually (FAO, 2006a). Degradation, defined as decrease of density or increase of disturbance in forest classes, affected tropical regions at a rate of 2.4 million ha/yr in the 1990s. |
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