Improving restoration heuristics to support anadromous fish passage

Area of Science:

• Freshwater ecology
• Conservation science
• Restoration ecology

Background:

• Global investments in river connectivity restoration are increasing to support freshwater biodiversity.
• Current restoration decisions often rely on simplified heuristic rules rather than optimization methods.
• These heuristics frequently use proxies for watershed connectivity and habitat quality, which may not be optimal.

Purpose of the Study:

• To evaluate the performance of common heuristic rules used in river restoration.
• To demonstrate how redesigning these heuristics can improve cost-effectiveness in restoration portfolios.
• To bridge the gap between optimization research and practical on-the-ground restoration efforts.

Main Methods:

• Case study of anadromous fish passage restoration in western Washington, USA.
• Benchmarking common heuristic approaches against outcomes from optimization methods.
• Analyzing the impact of different connectivity and habitat quality proxies on restoration gains.

Main Results:

• Heuristics using total upstream habitat as a proxy achieved 93% of optimal gains when only habitat quantity was considered.
• Incorporating habitat quality proxies (e.g., natural land cover) into heuristics reduced performance by nearly half.
• Optimization methods offer substantial performance gains over commonly used heuristic rules.

Conclusions:

• Commonly used heuristic rules for river restoration can be inefficient, especially when incorporating habitat quality proxies.
• Redesigning heuristics to more directly target high-quality habitat is crucial for improving investment efficiency.
• Improved heuristics are needed to enhance the effectiveness of freshwater biodiversity conservation through river restoration.