## 4 Results and Analysis
### Impact of Climate Change on Wetland Changes  
The statistic results of wetland changes in the TRH region during 1990 to 2012 show that wetland changes over two periods had different characteristics (Table 4). During 1990-2004, wetland changes took place mainly in the semi-arid and semi-humid regions (0.3 \(<\)_HI_\(<\) 1.0), accounting for 68.5% of the total wetland changes. In the Region I, the wetland changes were dominated by increases in lakes, reservoirs and ponds, those accounted for 90% of the regional wetland changes and 28.8% of the total wetland changes in the TRH region. In the Regions II, III and IV, wetlands obviously shrank, with the decrease in area accounting for 12% and 27.8% of the total wetland changes in the Regions II and III, respectively. According to the climate change during 1990-2012, generally the temperature went up and precipitation rose slightly in the whole region, but the trend showed spatial heterogeneity. Comparing the climate changes in the Regions I and II, we discovered that annual temperature trend rate almost  
Figure 10: Spatial distribution of annual _HI_ change rate in the TRH region. Figure 9: Spatial distribution of annual humidity index (_HI_) in the TRH region. stayed at the same level, and precipitation tendency trend differed significantly in that the rate increase tendency in the Region I was higher than that in the Region II. Taking climate change into account, the wetland change responses in Regions I and II were totally different, with wetland expanding in the Region I, but drying up in the Region II. Compared to the climate changes in the Regions II and III, the temperature rate tendency had a little discrepancy and the annual precipitation trend in the Region III was higher than that in the Region II. However, wetland changes in the two regions displayed a different response magnitude, in that the wetland decrease in the Region II was 15.8% less than that in the Region III. The above phenomenon suggested that wetland changes might be not directly related to temperature and precipitation changes. As was shown by the spatial distribution of the _HI_ tendency, the Region I had the maximum humidity trend rate as well as biggest wetland changes, therefore, the increase of lakes, reservoirs and ponds in this region was consistent with the climate humidification tendency. In addition, the _HI_ value in the Region II was higher than that in the Region III, accordingly, the magnitude of wetland decrease was smaller than in the Region III. Additionally, in the Region IV, the _HI_ showed a negative growth rate, which contributed to wetland decrease. Consequently, _HI_, reflecting drought and wetness condition, were the direct factor resulting in wetland changes in the whole region. During 2004-2012, the _HI_ increased in the THR region. Regions with _HI_ of 0.3-0.4 had largely disappeared, but the area of the humid region increased considerably (Table 4). Wetland changes were mainly distributed in the semi-arid region (\(0.2<HI<0.5\)) during this period, accounting for nearly half of the total wetland change area. Wetland changes mainly happened with the increase of lakes, reservoir & ponds in the Regions I, II and III, which accounted for 64% of the total wetland change area, double that in the former period.