README

Stephanie Peacock 2025-12-24

Quantifying Exposure of Pacific Salmon and Steelhead to Climate Change in the Fraser River basin

Background

Climate Change Vulnerability Assessments (CCVAs) estimate how climate change may affect key attributes of a system to guide conservation and mitigation priorities. In this project, we focus on the potential impacts of climate change on the viability of Pacific salmon and steelhead Conservation Units (CUs), aiming to identify which CUs are most affected and why. Our approach is data-driven, quantifying climate change exposure by incorporating the spatial and temporal distribution of CUs along with species- and life-stage-specific temperature sensitivities. While CCVAs typically include adaptive capacity, this assessment excludes that component; therefore, we refer to these as climate change exposure assessments. For more details, visit https://salmonwatersheds.ca/project/ps13/.

What’s in this repo

• The code and data are organized into freshwater and marine sub-directories because the data sources and processing for these two habitats are different.
• Within the freshwater and marine folders, there are R files in code that read in climate model projections, organize and summarize it, and calculate exposure for each CU, life stage, and climate attribute. These calculations have been applied for 60 CUs in the Fraser River basin.
• Raw data files consist of Global Climate Model projections and are large files (hundreds of GB). These are therefore not made available on GitHub but can be downloaded from the relevant sources listed in the table below or by contacting the project lead (Stephanie Peacock, speacock at psf dot ca).

Environment	Exposure attribute	Definition	Dataset
Freshwater	Stream temperature	The number of days within each life stage that stream temperature is above a species- and stage-specific upper threshold	Pacific Climate Impacts Consortium gridded hydrologic model output
Freshwater	Low flow	The number of days within each freshwater life stage that flow is below 20% of the Mean Annual Discharge (MAD) for the grid cell	Pacific Climate Impacts Consortium gridded hydrologic model output
Marine	Sea surface temperature	The number of months that SST is above the “core thermal range” during the marine stages. Core thermal range was defined by Langan et al (in review) based on ocean habitat use by each species.	NOAA’s Climate Change Web Portal
Marine	Sea surface salinity	The number of months that salinity was below the 2.5 percentile of historical salinity within each grid cell (i.e., had a z-score of less than -2).	NOAA’s Climate Change Web Portal

Draft outputs

The docs folder contains

• Supplemental material (online-supplement.Rmd) published online at https://bookdown.org/salmonwatersheds/climate-change-exposure-supp/online-supplement.html
• Functions to produce paper figures and supplement figures in online-supplement-functions.R
• map-for-paper.R is code for a map that has a point at the centroid of each CU boundary, shaded according to overall exposure (Figure 2)

The shiny folder contains

• An R Shiny document (app.R) that allows users to explore draft results, published online at https://salmonwatersheds.shinyapps.io/climate-change-exposure/

Acknowledgements

This work is funded by the BC Salmon Restoration and Innovation Fund. We are extremely grateful to PSF’s Climate Science Advisory Committee, who have provided input on our approach. We thank Markus Schnorbus at PCIC for providing preliminary hydrologic model outputs so we can advance this work.