# Quantifying Climate Change and Ecological Responses within the Yangtze River Basin, China
## 4 Discussion  
Climate change and its impact on terrestrial ecosystems is a major area of concern for global change science. A key aspect is the analysis of spatiotemporal changes in climatic parameters and ecological indicators and their relationships. In this study, we have combined the data outputs from six models from CMIP5 with observed meteorological data to determine the trends, and we have explored the evidence for climate change at local and global levels. In addition, the spatiotemporal trends of various ecological factors were analyzed, and correlation analysis was used to analyze the impact of climate change on the ecological factors. Compared with previous studies, which have tended to focus on a single vegetation index, we have used a variety of vegetation indices and determined their relationship with climate change on different timescales (annual and the growing season) to provide a more comprehensive analysis of the impact of climate change on ecological factors. [PERSON] et al. (2017) confirmed vital increases in NPP under the warmer and much wetter scenario in California. In a similar study of Hubei Province, in the middles reaches of the YRB, [PERSON] et al. (2017) found that increases in GPP, NPP and LAI were significantly correlated with temperature but there was no correlation with precipitation. The absence of a relationship between precipitation and ecological factors may be because there is abundant precipitation in the area and, therefore, water availability is not a limiting factor for vegetation ([PERSON] et al., 2017). However, in areas with less rainfall, increases in temperature will result in increased evaporation which may restrict vegetation growth. In the present study we found a positive correlation between NDVI and precipitation for the Tibetan Plateau in the upper reaches of the YRB; in contrast, however, there is a negative correlation between NDVI and temperature ([PERSON] et al., 2017). In addition, delta annual EVI (urbanization effects, urban EVIs minus rural EVIs) exhibited a significant decreasing  
Figure 17: Results of correlation analysis of climatic and ecological parameters for the YRB. (**a**) Annual mean NDVI and annual mean air temperature/annual precipitation; (**b**) mean growing season EVI and mean air temperature/total precipitation in the growing season; (**c**) annual mean LAI and annual mean air temperature/annual precipitation; (**d**) annual mean air temperature and annual total GPP/NPP. Significance levels: *** means the significant of the 99% confidence interval, \(p<0.01\), * means the significant of the 95% confidence interval, \(p<0.05\). trend for nine of the 10 provincial capital cities (\(p<0.05\)) in the YRB [49], especially, Shanghai, Nanjing, Hangzhou, etc. Climate change (including changes in temperature and precipitation, and increases in extreme climate events) and human activities together affect the spatiotemporal variation of ecological indicators [50; 51]. Although vegetation changes are usually related to climatic factors, the relationship between vegetation and climate is often unclear in areas that are strongly influenced by humans [52]. For example, in the YRD, despite the significant increasing trend in temperature, ecological factors exhibit a significant decreasing trend (Figures 13, 15 and 17), in accord with the results of [PERSON] et al. [53] who concluded that rapid urbanization has resulted in a sharp decrease in the NDVI over the YRD. The impact of human activities on vegetation generally includes two aspects: direct changes in vegetation resulting from artificial afforestation, deforestation, crop planting or harvesting, and human-induced land-use change; and the other is indirect impacts on vegetation [54; 55; 56; 57; 58]. For example, human-induced land use changes and greenhouse gas emissions may cause climate change at the local, regional, and global scales which have further affected vegetation growth and composition [59].