Impacts of cascade hydropower development on river ecosystem homeostasis: A review

Cascade hydropower development is an important requirement to promote energy revolution and strengthen clean energy development worldwide. However, ecological conservation has become one among many major factors restricting hydropower development and the problem of green development must be solved crucially, from the perspective of the overall ecosystem. Simultaneously, the lack of a comparative basis has become the bottleneck problem limiting research on the ecological impact of cascade hydropower development. This review synthesizes the variation of river ecosystem homeostasis under hydropower development, highlighting that both the ecosystem structure and function should be considered. According to the definition of ecosystem homeostasis, a multidimensional framework, including temporal stability, resistance, resilience, and recovery perspectives of ecosystems, to completely uncover homeostasis under hydropower development is proposed. Moreover, the cumulative effect of cascade damming on river ecosystem homeostasis is analyzed based on both long- lasting and synergistic spatial effects of cascade reservoirs. The interaction between biogenic substances and ecosystem homeostasis is also discussed and the driving mechanism of homeostasis evolution of river ecosystem is revealed. Furthermore, our study also suggests that network analysis and biological source tracing methods can be applied to quantify the effects of cascade hydropower development on ecosystem homeostasis in future studies. This review is intended to help ecologists, regulators, and others to make informed decisions regarding the rational utilization of hydropower resources, ecological protection, and restoration of hydropower development worldwide.