## 5 Conclusions and Discussion  
The TRH region is one of China's most important regions with concentrated wetland distribution. As an ecosystem with distinctive features, wetlands in the TRH region play an irreplaceable role in water source conservation, run-off adjustment and biodiversity maintenance. The wetland changes and its response to climate in the TRH region were analyzed based on climate data and remote image data from the early 1990s to 2012. The main conclusions can be summarized as follows:  
1. In the TRH region, wetlands occupied 6.3% of total land area in 2012. Swamps, streams & rivers and lakes were the dominant wetland types in the region. The Yangtze and Yellow River basins had the most extensive distribution of swamps, which accounted for 49.8% and 36.8% of the total wetland area in each basin, respectively. Streams & rivers were most extensively distributed in the Langcang River basin, accounting for 63% of total wetland area in this basin. 2. Wetlands have undergone great changes since the early 1990s. The total wetland area increased by 260.6 km\({}^{2}\) (1.2%). Lakes, reservoirs & ponds displayed a continuous increasing trend, but swamps, streams & rivers show a continuously decreasing trend. The wetland area in the Yangtze River basin showed an overall increasing trend, while in the Yellow River and Langcang River basins, the wetland areas decreased in general. From the early 1990s to 2012, the wetland changes showed a shifting trend from the middle parts to the western parts. Wetlands in the middle and western parts varied significantly during these years. 3. In the past 20 years, the climate in the TRH region has turned from Warm-Dry to Warm-Wet. The average temperature and precipitation increased by 0.9 \({}^{\circ}\)C and 102 mm, respectively, from 1990 to 2012, and the average _HI_ increased by 0.1, showing an upward trend and a shift of the dividing line towards the northwest in both the areas of the semi-humid and semi-arid zones. 4. By correlation analysis of wetland changes with meteorological factors from 1990 to 2012, the results indicated that wetland changes might be not directly related to temperature and precipitation changes. The regional humidity differences and the interannual variation trend, caused by the change of precipitation and evaporation, was the main driving factors for the dynamic variation of wetland changes in the TRH region. In the general, the increase of _HI_ in the THR region since the 1990s, especially in the western TRH region, has contributed continuously to the wetland increases. Wetland dynamics are the consequence of the interactions among various factors, such as geological structure, climatic conditions and supplement patterns. Climate change, especially temperature, precipitation and humidity, observably impacts the wetland changes. Generally, in the TRH region _HI_, which changes with precipitation and evaporation, is the primary climatic factor affected wetland changes, and the good consistency between the regional _HI_ and the change trends of wetland are presented as controls on the wetland balance during the last 20 years. We can see that the obviously increasing _HI_ in the northwestern TRH region (4.3/year in region I during 1990-2004 and 17.3/year, 20.4/year and 10.4/year in the Regions I, II and III, respectively, during 2004-2012). This trend was directly related to the expanding lakes, reservoirs and ponds in this region. However, although the _HI_ (2.1/year and 1.8/year, respectively, during 1990-2004) in the Regions II and III increased, swamps mainly showed shrinking trends. Therefore, swamp changes in these regions were primarily controlled by other factors, and the increasing _HI_ was not obviously related to the decrease of swamp area, but rather the degree of increase of the _HI_ affected the degree of decrease of swamp area in these regions.