3.2.4 Forest fire. Forest fire is one of the most severe threats to forest diversity in China. In 1991, forest fire area was 22,200 ha, which increased by 53.9% compared to 1990, with an increasing frequency of 3.8%. The biggest fire in 1989 covered 1.33 million ha of cold-temperate forests, resulting in a reduction of the regional forest coverage from 76% to 61.5%, and a loss of mother trees, young seedling and wildlife therein.

3.2.5 Forest pests and diseases. There are 6,500 different forest pests and diseases in China, of which more than 200 forest pests and diseases are widely spread and cause great threats to forest biodiversity. The damaged forests due to the attach of pests and diseases had been steadily increasing over the period of time from 1987 to 1991, with an annual increasing rate of 3-4%. In 1987, for example, the forest area damaged by pests and diseases was 9.375 million ha, which was more than the total planting area in the same year, and the consequent loss was equivalent to the total annual budget allocated to forestry sector.

3.2.6 Mono-culture practice. In recent years, the plantation area increased by 2.78 million ha, from the previous 31.01 million ha up to the present 33.79 million ha, with an annual average increment of 650,000 ha, which accounts for 31.86% of the annual average increment of the total forest area. The plantation area in China makes up one fourth of the total forest area, ranking first in the world. The impacts of plantation forestry on biodiversity are as follows: a large and pure plantations develop at the expense of natural forest resource, leading to damage or fragmentation of natural forests. In addition, plantation forests are established with single dominant species and simplified structure, rather than high species diversity of plants and animals and multiple spatial layers.

3.2.7 Environmental pollution. Air pollution is currently considered as the most serious threat to forest biodiversity relative to other pollutants. Most of the problem comes of China’s increasing industrial sector and from vehicles, especially acid rain, which widely and frequently occurs in southern China. According to statistics, forest area affected by acid rain in Sichuan province is 275,600 ha, of which about 15,000 ha of forests has died due to acid rain, accounting for 31.9% and 5.7% of the forested area, respectively. In Guizhou, forest area polluted by acid rain is 140,500 ha, leading to an annual economic loss of 500 million Chinese yuan.

3.2.8 Illegal poaching and hunting. For years illegal poaching and hunting of endangered animal and plant species have been rampant in China. Because of random hunting and poaching, illegal trading and smuggling, population sizes of many animal and plant species have greatly reduced and many of them are put on the China’s Red Data Book. In Sichuan, for example, there were 171 poaching cases of wildlife in 1988.

3.2.9 Herbs and economic plants gathering. There are many plants of medical, edible or industrial value living in forests. Due to random gathering and over-harvesting, many species of such plants have become extinct, rare or endangered.

3.2.10 Loss and fragmentation of habitats. As a result of over-exploration of forests, the suitable habitats become reduced and fragmented into small patches, the wildlife in them become more and more vulnerable to various stresses and have difficulty in their reproduction and survival. In the same way, species that are restricted to isolated or fragmented patches of suitable habitat have to change their population structure and their population sizes decreased dramatically. In Hainan Island, for example, after the replacement of natural regenerated forests by rubber plantation, the suitable habitats required for peacock and Cervus eldi were greatly reduced, and therefore these species become extinct. In addition, the fragmentation of habitats also has a large effect on genetic diversity. The joint investigation made by China Ministry of Forestry and World Wildlife Foundation during 1986 and 1988 indicated that the suitable habitats of giant panda was completely lost in sixteen counties and the remaining habitats were only about 11,000 km2, distributed separately in 34 counties. As a result, the population of giant panda was divided into 24 sub-populations and the sequent genetic inbreeding of these isolated sub-populations would definitely occur, putting the giant panda at risk.