From Fragmented Metrics to Watershed Governance: Scientists Redefine How We Heal Aquatic Ecosystems

Aquatic ecosystems worldwide are facing accelerating degradation from climate change, human activity, and watershed development. Conventional assessment methods—evaluating water quality, biology, and habitat in isolation—remain fragmented and retrospective, missing the cross-scale interactions that drive ecosystem collapse.

In a new review article published in Water & Ecology, a research team led by Qiuwen Chen from Nanjing Hydraulic Research Institute proposed that watershed aquatic ecosystem health should be understood as a combined social–ecological and process-based property, rather than as a simple aggregation of water-quality or biological indicators.

“The main problem is fragmented diagnosis,” says Chen. “We track chemistry, species loss, and physical damage separately, yet none of these snapshots can reveal why the system is failing or where it is heading. We must treat the watershed as a coupled social–ecological system.”

Drawing on bibliometric evidence from the Web of Science and the China National Knowledge Infrastructure (CNKI), the authors traced how international frameworks—from the U.S. Rapid Bioassessment Protocol to the EU Water Framework Directive and China's evolving river health initiatives—have expanded assessment coverage. Three persistent bottlenecks remain: 

1. Critical mismatch between short-term, localized observations and long-term, basin-scale processes;

2. Limited mechanistic understanding of how hydrological, biogeochemical, and ecological processes interact; and

3. Weak translation of scientific knowledge into management practice.

The review brought together three parallel research strands—biological integrity, habitat structure, and governance. “Only by integrating these dimensions can assessment move from static reporting to anticipatory decision-making,” says Chen.

In particular, four frontiers are reshaping the field:

• Climate change demands non-stationary baselines;
• Artificial intelligence and remote sensing can integrate heterogeneous data and predict nonlinear responses, but only when coupled with process-based understanding rather than deployed as black boxes;
• Molecular ecology techniques such as environmental DNA enable comprehensive biodiversity monitoring across vast basins; and
• Nature-based solutions shift the focus from engineering-based pollution control to restoring self-organizing ecosystem processes.

The authors noted that the urgency is acute in China, where heavily engineered rivers, multi-source pollution, and climate extremes create complex trade-offs. “While China has advanced in digital twins and large-scale restoration, assessment must evolve from single-objective engineering to process-oriented governance that coordinates water resources, environments, and ecosystems across entire basins,” Chen explains. “Aquatic ecosystem health is not a biophysical scorecard—it emerges from interactions among ecology, land use, economics, institutions, and public values.” 

The authors urged that future progress should include linking structure with process, science with governance, and upstream protection with downstream well-being.

Contact the author: 

Qiuwen Chen

-Center for Eco-Environment Research, Nanjing Hydraulic Research Institute, Nanjing 210029, China

-Yangtze Institute for Conservation and Development, Hohai University, Nanjing 210098, China

qwchen@nhri.cn

Funder:

This research was supported by the National Natural Science Foundation of China (52121006, U2340220, U25A20359) and the Fundamental Research Funds for Central Public-interest Scientific Institutions (Y925002, Y925003).

Conflict of interest:

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

See the article:

https://doi.org/10.1016/j.wateco.2026.100050