Climate change impacts on the topography and ecological environment of the wetlands in the middle reaches of the Yarlung Zangbo-Brahmaputra River.

• A high-precision 2-D flow and sediment transport model of the Yarlung Zangbo-Brahmaputra River is established. • A comprehensive habitat suitability evaluation system is developed. • Climate change will lead to sediment deposition and wetlands degradation in the study area. • The ecological environment of the wetlands will be deteriorated due to climate change. The Yarlung Zangbo-Brahmaputra River originates from the Tibetan Plateau. Its hydraulic conditions and ecological environment affect the economic, agricultural development and ecological environmental protection of many countries. So far, studies analyzing the impacts of potential climate change on hydrological and water resources conditions in the Yarlung Zangbo-Brahmaputra River Basin are limited. Most of these studies analyzed the overall basin condition at the large and coarse scale. Research on the response of the topography and ecological environment at high spatial resolution scale in river reaches and wetlands to climate change in this area has not been conducted before. In this study, we developed a two-dimensional flow-sediment transport model to simulate the flow and sediment conditions in the middle reaches of the Yarlung Zangbo-Brahmaputra River with the hydrological conditions predicted by a meteorological-hydrological model. We then analyzed the impacts of potential climate change on the riverbed and wetland topography in this region. We further designed a habitat suitability evaluation system to evaluate and compare the ecological environment of the wetland under current climate conditions and with potential climate change. Our research shows that climate change scenario RCP4.5 will result in about 40–90 million cubic meters of sediment deposition in wetlands each year in the next 6 years. The elevation of the main channel will decrease, while the elevation of shoals will increase, which will indirectly lead to wetland degradation. The difficulty of foraging will be increased, and the area available for fish to rest will decrease. Ultimately, the habitat environment of fish will be destroyed and the density of fish populations will be lower. The impact on migratory birds is more complicated. It is expected that the migratory birds' living environment will improve in July (since both selected habitat suitability metrics show a trend of improvement), but it will be worse than the current condition in other months. [ABSTRACT FROM AUTHOR]