Remote Sensing Monitoring And Analysis Of The Changes Of Mangrove Forests Resources In China In The Past20Years

Mangrove forests, which naturally distribute in tropical and sub-tropical coastal wetlands, are woody plant communities and peculiar plant types in beach as well as a significant coastal wetland resource. Mangrove forests not only provide important ecological habitats for wetland species, but also have the effects of reducing wind power, protecting bank, eliminating pollution and preserving biological diversity.In China, mangrove forests distribute along the coasts of Zhejiang Province, Fujian Province, Guangdong Province, Guangxi Province, Hainan Province, Hong Kong, Macau and Taiwan Province. We select Zhejiang, Fujian, Guangdong, Guangxi and Hainan Province as the study area, and choose the Landsat-5TM, Landsat-7ETM+and HJ-1CCD remote sensing images which acquired in1990,2000and2010respectively as data sources. Addition with the field data which was undertaken in2008, we monitored the mangrove wetland resources in the above province in the past20years, and analyzed the temporal and spatial changes. The results are as follows:1) In the above5province of China, mangrove forests area was13519.6hm2in1990,16053.6hm2in2000and24578.2hm2in2010. Among the5province, Guangdong has the largest existing mangrove forests with the area of almost a half. In contrast, Zhejiang Province has only1‰of all the monitored mangrove forests.2) Mangrove forests experienced the greatest changes in Guangdong(4397.7hm2increase) and Guangxi Province(1492.3hm2increase) from1990to2000and from2000to2010respectively. The monitored results indicate that although the area of the mangrove forests increasing in the past two decades, but the distribution range getting concentrated according to more and more mangrove conservation established.3) The changes of mangrove forests are caused both by the human and natural factors. The natural factors contain biological invasion, the rising of sea level, plant diseases and insect pests, etc. The human factors consist of sea reclamation, nature reserve establishment, laws, tourism development, catching and grazing without planning, etc. Among them, sea reclamation is the main reasons for mangrove forests degradation. The best way of increasing mangrove forests is to establish nature reserve.