Mountain Research and Development 26 (3), 227-236, (1 August 2006) https://doi.org/10.1659/0276-4741(2006)26[227:FCALUC]2.0.CO;2
KEYWORDS: classification, forest cover, land use change, land cover change, remote sensing, GIS, Yunnan, China
Contrary to the trend of rapid deforestation continuing across Asia, regional assessments point to recent increases in forest cover in China, including Yunnan Province, since the implementation of dramatic forestry policy changes. There is debate about whether the statistics that describe increasing forest cover adequately account for forest status and quality. In this context, the present article aims to quantify forest cover and land use changes in a Tibetan-dominated rural township in northwest Yunnan, China—an ecologically important region affected by recent forest policy changes. Three sequences of Landsat satellite imagery dating from 1981 to late 1999 and other digital datasets were used in a rules-based hybrid classification approach, achieving acceptable accuracy assessment scores.
The results show an average aggregate decline in conifer forests of 23%, mostly due to an active logging industry. Much of this forest has converted to shrubland, which increased in area by over 100%. Grassland also increased, mainly at the expense of cultivation, as a response to increasing dependence on livestock by the rural communities, although high elevation rangelands decreased in area due to changing livelihoods and restrictions by the government on grazing and deliberate burning. Using the accepted definitions of forest and shrub-land categories, it was difficult to depict forest and shrub-land dynamics due to variation in forest regeneration and afforestation, dieback-affected forests, secondary succession of disused rangelands, and a variety of other mixed community types. Conversion analysis revealed significant forest–shrubland exchanges occurring even during the 1990s when reduction in overall forest cover slowed considerably. The results support the view that the standard categorizations and representations of land cover only portray a partial picture of forest status, as they do not account for multiple conversions that occur between different land covers over time. Due to ongoing forestry programs and increasing utilization of forest resources by local communities, these conversion issues may be significant, with implications for forest quality and biodiversity.
Our understanding of China's forest status will be improved by correlating inventory data with finer-scale spatial datasets to enable conversion analysis in representative ecological regions. This will advance our knowledge of China's forest status and the effectiveness of forest policy for both local rural community needs, as well as for broader ecological conservation.