| China is one of the countries bearing the most forest bio-disaster damages and losses in the world. From forest sustainable management view, the results of economic losses evaluation is urgently desired by farmers, forest managers and governments at different level, for they need to balance control costs and economic impacts of the disaster. They also need to know if their control measurements can have non-harmful impact on environment. Up to now, there are little research data for estimating economic losses of forest bio-disaster at nation or region level.In this paper, the definition, classification, rank, evaluation theory and methods for forest bio-disaster were studied. Forest bio-disaster is caused by animals, plants and microorganisms in forests. It was classified as 4 types according to the causes, symptomatology and the disaster performance. The direct economic losses mainly include live tree growth deduction, timber volume losses and grade decline, non-wood products losses and grade decline. Calculating equations and formulations for estimating forest bio-disaster were deduced by the combination of China forest pest statistic criteria and loss assessment data of different single forest pest, emending with pest statistic data, forest growth data and non-wood forest products data during 2002-2006 in different provinces. The main results of this paper were showed as follows:The essence of China's forest bio-disaster The forest biodisaster in China is a kind of ecological disaster mixed with natural elements. Irrational management of forest is the main cause of the disaster. Forest bio-disaster theory was put forward such as inevitability, periodicity, non-paroxysmic, accumulative, predictible and controllable.Calculating for the loss of forest biodisaster 62 sets of calculating equations and formulations for estimating losses of forest bio-disaster were deduced which will provide tools for China every provinces.Forest bio-disaster were classified as 4 typesⅰ)Forest growth deduction. The causes of the disaster, including defoliators, scales and aphids, shoot damagers, foliage and shoot diseases pathogen, blocked or destroyed photosynthesis of the plants.ⅱ)Timber grade declined. The causes of the disaster, including borers, scales and aphids, root damagers, trunk and root diseases, destroyed the xylem of the plants.ⅲ)Non-wood forest products losses. The causes of the disaster, including tree seed and cone pests, diseases and insect pests damaging economic forests, destroyed seed and cones as well as economic forests.ⅳ)Tree death. The causes of the disaster, including bark and phloem damagers, root diseases and insect pests, tree borers, trunk diseases,vascular damagers and rodents, gave rise to the collapse of a tree or forest.Forest bio-disaster rank Forest bio-disaster can be ranked as 4 grades—gigantic disaster, great disaster, medium disaster and little disaster by 4 kinds of absolute criteria and 2 kinds of relative criteria. The absolute criteria include infested areas, damaged areas, incidence and direct economic losses. The relative criteria are the ratio of the damaged areas to forest areas and the direct economic losses to GDP in the occurred region. Gigantic disaster means that the annually infested and damaged areass exceed 100 thousand hectares, the direct economic losses more than RMB 100 million Yuan and the incidence relating to the whole country. Great disaster indicates that the annually infested and damaged areas between 10-100 thousand hectares, the direct economic losses between RMB10-100 million Yuan and the incidence relating to more than one drainage areass or cross provinces. The infested and damaged areas, the direct economic losses and the incidence for medium disaster was defined as 1-10 thousand hectares, RMB 1-10 million Yuan annually and within a province, respectively. Little disaster was that the annually affected and damaged areas no more than 1000 hectares, loss less than RMB 1 million Yuan and the incidence at local level.The results of the estimationⅰ)The infested areas of forest bio-disaster during 2002-2006 (not include Tibet, Taiwan, Hongkong, Makao data ) was 9.5 million hectares per year, occupied 3% of the total forest areas in China. The damaged areas occurred 4 million hectares annually and the damage ratio was 42.57%. The average timber volume loss was 22 million cubic meters per year, occupied 0.1% of living forest stand volumes in China. The annually non-wood forest products losses was 890 million kg and the total loss values of timber, bamboo and non-wood forest products was RMB 32.9 billion Yuan.ⅱ)The infested areas of pine caterpillars was 1.3 million hectares, occupied 12.3% that of the total forest bio-disaster infested areass. The average timber volume loss was 2070 thousand cubic meters per year, occupied 9% of the total timber losses of forest bio-disaster in China. The annually resin harvest loss was 73 thousand kg and the total loss values of timber and resin was 3 % of the total loss values caused by forest bio-disaster in China. The infested and damaged areas of poplar defoliators and borers were in the range of 8%-12% that of the total forest bio-disasters in China, but the economic value losses is only 1% of the total.
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