Fig. 5.(a) The shift of the population centroid in the suitable area and (b) mean suitability change and the habitat change in different scenarios
  1. Discussion

    The effect of climate change

The result demonstrates that the habitat area of migratory birds will significantly reduce in future, which mainly due to climate change (Gill et al., 2019). Migratory species are more responsive to climate change, as their migration process may be closely related to climate (Dunn et al., 2009).
In summary, temperature plays a great role on the distribution of migratory birds. Therefore, we investigated the importance of environmental variables in 3 different climate zone (east part of south temperate zone(STZ), middle subtropical zone(MSZ) and middle tropical zone(MTZ)). Simultaneously, the environment variables differences in 6 basin (Haihe River Basin, Yellow River Basin, Huaihe River Basin, Yangtze River Basin, Southeast Basin and Pearl River Basin) were also considered. We selected the most important variables firstly and then calculated the percent contribution of variables to figure out the constraint of migratory birds in different regions.
4.1.1 How does climate influence the basins?
The habitat area will decline most in the Yangtze River and Pearl River basins of the southern and the area will increase most dramatically in the Huaihe River basins (Fig.6). The area of habitat loss in the Yangtze River basin will reduce mostly 58880\(\text{km}^{2}\)in future. The Pearl River basin and the Yellow River basin will decrease 34589\(\text{km}^{2}\) and 10287 \(\text{km}^{2}\) in future. Yangtze River basin will loss 9.74% of the total habitat area in the basin. Pearl River basin will loss 13.21% of the total habitat area in the basin. And Yellow River basin will loss 9.83% of the total habitat area in the basin. The habitat area of the Huaihe River basin will increase 13218\(\text{km}^{2}\), accounting for 8.16% of the total habitat area in this basin. The decrement of habitat leads to the overlap of living spaces between birds and humans (Flottum et al., 2016; Short et al., 2011).