Downscaling climate projections to forecast ecological changes in river systems

Area of Science:

• Ecology
• Climate Science
• Conservation Biology

Background:

• Freshwater ecosystems face degradation from climate change, with limited predictive assessments integrating thermal stress and habitat fragmentation.
• Atlantic salmon (Salmo salar) populations are vulnerable to rising temperatures and hydrological instability.

Purpose of the Study:

• To evaluate the combined impacts of rising maximum summer temperatures (Tmax) and precipitation variability on Atlantic salmon in Newfoundland and Labrador.
• To integrate downscaled climate projections with river connectivity assessments to predict future habitat suitability and fragmentation.

Main Methods:

• Utilized high-resolution climate models (ClimGen) to project Tmax and precipitation shifts.
• Employed the Dynamic Connectivity Assessment Tool (D-CAT) to quantify climate-induced thermal stress and migration barriers affecting river connectivity.
• Assessed 13 case study rivers to identify geographic variability in climate vulnerability.

Main Results:

• By 2090-2094, over 70% of rivers are projected to exceed the 22°C thermal stress threshold for salmon, with some reaching lethal limits (>25°C).
• Increasing precipitation variability is expected to amplify hydrological instability through drought and sedimentation.
• Over 70% of in-stream barriers are located in high-Tmax regions, severely restricting salmon migration routes and access to critical habitats.

Conclusions:

• Integrated climate adaptation strategies, including barrier mitigation, adaptive hydrological management, and riparian restoration, are crucial for improving freshwater connectivity.
• Addressing uncertainties in short-term climate extremes and species-level adaptation is essential for effective conservation planning.
• The study highlights significant geographic variations in climate vulnerability, necessitating tailored regional management approaches.