## 5 Discussion and Conclusions
### Discussion
Therefore, from the early 1990s, when the temperature started to rise, the LULC in the headwaters of the Yangtze River began to change in a positive way. However, glacier retreat and permafrost thawing owing to a rise in temperature would pose a threat to the balance of the natural ecosystems, which is another serious issue that needs to be solved urgently. The majority of the literature suggests that LULC change would introduce substantial change to the ecosystem. Research in Dhaka revealed that unplanned and rapid urbanization had a possibility of inducing many environmental adversities in the near future, such as serious urban flooding, highly fragmented landscape, a decline of landscape diversity and a decrease of green space [33; 43; 44]. Deforestation would cause an increase in annual runoff and a decrease in annual evapotranspiration in Southern China [7]. The reduction of forest and expansion of urban and build-up area has influenced the carbon balance in North Korea [45]. A substantial (20%-50%) decline across ecosystem services as a result of land-cover change in the Little Karoo was also reported [32]. In the TRHR, many researchers have conducted studies on the LULC and the ecosystem and their services as well. During 1995 to 2000, land use contributed about 58% to the water supply decrease because of the intense human activities in the Yellow River Source Area, and contributed about 61% to the water supply increase from 2005 to 2008 with improved vegetation coverage conditions and the water retention ability after the implementation of the ecological projects [46]. Grassland degradation resulted in great carbon emissions in the TRHR before 2004, but grassland restoration after 2004 sequestered carbon 4.4 times more than that before 2004 [25]. Although the LULC has changed in a positive way, we are still a long way from achieving a full recovery of the ecosystem in the headwaters of the Yangtze River and Yellow River. The vegetation coverage is increasing, but it is not obvious that the community structure has improved [20]: Overgrazing is still severe, which is one of the main causes of grassland deterioration [47]; an increase in precipitation could promote vegetation growth, but the erosive force of rainfall has also been strengthened [38]; and, with further increases in temperature, the climate could gradually show a warming and drying trend, which would inhibit the growth of vegetation [24]. Further, while the water supply capacity has clearly increased, besides the increase in precipitation, the melting of glaciers and permafrost due to the rising temperatures has also increased the runoff, which is unsustainable and could threaten the local ecosystem balance. Therefore, the ecosystem protection in the second stage of the ecological projects should be sustainable and spatially targeted to maximize the benefits; meanwhile, the philosophy of social engineering should also be employed [40]. It must be noted that, due to the limitation of expert knowledge, similar spectral characteristics of different LULC types [44], blurred texture feature, data resolution and the complexity of classification, the possible inaccuracy is difficult to subdue, especially for the MSS images because of its coarse spatial resolution that leads to spectral mixing of different land covers [17]. Given those limitations, we have tried to minimize the inaccuracy by constructing the LULC datasets of the late 1970s, the early 1990s and 2012 based on the LULC dataset of 2004 and change information extracting directly from the comparison between RS images in the late 1970s, the early 1990s and 2012, and the RS images in 2004. During the classification process, the expert knowledge, the geographic condition and other auxiliary data like vegetation maps, grassland maps and topographic maps were fully obtained. Meanwhile, the LULC dataset of 2004 underwent careful and rigorous visual inspection, and were compared with the original images and field investigation data.