A complementary measurement of changes in China’s forestry area using remote sensing data

Abstract

Based on the official government statistics, during 1980s until 2000 China's forest cover and the forest quality has been improved steadily. Despite this is a seemingly optimistic trend, however, China's leaders have been introducing new forest policies to restrict timber harvest and increase forest cover. In light of this seemingly contradictory setting, we adopt another methodology to measure the increase or decrease of the forestry area by providing the first detailed statistics for changes in forestry area for the entire China using remote sensing data (Landsat TM/ETM digital images), and attempt to complement the official government statistics. We tracked the changes in forest cover from late 1980s through 2000 and estimated rates of forest cover changes and conversions between forestry areas and other land uses during this period. Our results reveal that during this period, the forest cover in China continued to decrease by approximately 1.15 million ha, or 0.5%. This result is in stark contrast with the official government statistics which reveal that the forestry area increased during this period. Importantly, we find that the two data sets are more consistent for provinces with large areas of forests, while the discrepancy is larger for provinces with small forest areas. We analyzed that some reasons identified may explain this discrepancy. Our results suggest that the two data sources are complementary for future monitoring of forest cover in China.