Spatial and temporal distribution of grassland and human occupancy condition in China from 2001 to 2009

Based on the MODIS land cover data sets, we studied the impacts of human activities on distribution of grassland, cropland and the potential natural vegetation (PNV) in China. The results showed that the cropland area dropped from 1.445×108 ha in 2001 to 1.425×108 ha in 2009. The maximum area——1.543×108 ha was in 2005 and the minimum area ——1.363×108 ha was in 2008. The grassland area decreased from 4.201×108 ha in 2003 to 4.032×108 ha in 2009 during the research period. In total, the decreasing rate of cropland area (13.49%) was greater than that of grassland (3.29%). The rate which grassland converted to arable land decreased by 4.96% per year, however, the rate converted to other land cover types increased by 20.87% per year. The rates of which cropland converted to grassland and other land cover types were similar. The rates of other land cover types converted into grassland (15.43%) and cropland(2.45%) decreased gradually year by year. The intensity of human occupancy of PNV increased during this research period which was relatively more intensive for grassland (38.18%) and forest (37.36%) among PNV categories.