Evaluating the vulnerability of freshwater fish habitats to climate change and identifying regional adaptation strategies in the Cariboo-Chilcotin

The Problem We Aimed to Solve

Studies have showed that climate change is affecting the temperatures in the north and during the winters as well as changing the levels of precipitation during the dryer and summer seasons. Temperatures are predicted to increase 2.5 °C, and precipitation is predicted to increase 5-20% and summer precipitation is expected to decrease by as much as 5% in Cariboo-Chilcotin. These changes create implication on physical conditions that impact ecosystems and wildlife. Impact on forest cover, snowpack, glaciers, and stream flow ultimately will impact habitat conditions and reproduction for freshwater fish. Adaptation strategies on land and water by human activity, an additional stressor, can be implemented to mitigate the effects of climate change.

ESSA’s aim was to increase the information available to describe the vulnerability of freshwater fish habitats to climate change to best inform decision making, and identify opportunities for adaptation that could help benefit people and freshwater ecosystems for the long term.

How We Helped

ESSA was engaged to assess the vulnerability of Pacific salmon to climate change within the Central Interior of British Columbia using climate change predictions under different future scenario. The work advanced modelling of watershed vulnerability to climate change by quantitatively linking climate variables (predictions of air temperature and precipitation from Global Circulation Models (GCM) and downscaled results) to stream conditions (water flow and temperature) to understand potential changes in salmon populations. ESSA’s efforts included collaborating with local stakeholders and a technical working group, from which the results of the vulnerability assessment were linked to regional decision-making processes to develop adaptation strategies that benefit human communities, Pacific salmon, and their freshwater habitats in the long-term given the anticipated effects of climate change.

In particular, the project established:

• a strong technical foundation from which to understand vulnerability of salmon watersheds and identify opportunities for adaptation across the region; and
• linkages to local collaborators / users who are hungry for credible climate change information to improve current management and use it as a catalyst enhance the profile of aquatic resources in regional planning.

Our Project’s Impacts

The methodology consisted of (1) experts to guide the assessment of vulnerability and analysis of adaptation so it could best be tailored for decision making, (2) updating information sources and methods for assessing vulnerability, and (3) analysis of existing data layers to identify adaptation opportunities.

1. Expert review included a group of 11 technical experts with local knowledge of the Cariboo-Chilcotin. Expertise ranged from fisheries, forestry, planning, hydrology, water management, and familiarity with regional planning agencies. A survey was deployed to compile feedback on four topics: (a) prioritizing adaptation strategies; (a) identifying indicators of adaptation potential; (c) identifying metrics of freshwater vulnerability; and (d) identifying appropriate administrative units for summarizing adaptation information. These were followed up with phone conversations, and an in-person technical meeting in Williams Lake to present the results of the vulnerability modelling and analysis of adaptation. The resulting analyses were supported by expert validation and advice for how to present the information in a meaningful manner to support planning and decision-making.
2. Assessing vulnerability involved using climate projections from four GCMs, and 3 emissions scenarios downscaled for regional scale, and a physically-based macro-scale hydrologic model was developed to predict flow at 58 stream locations across the study area. Air temperature predictions, fish observations, barriers, and channel characteristics information were also included for specific freshwater fish (bull trout, Chinook salmon, and Coho salmon). Model predictions were compared against fish habitat criteria to determine the accessibility and suitability of freshwater habitats from a historic reference (1961-1990) to three future time periods (2020s, 2050s, and 2080s)
3. Adaptation opportunities were identified based on expert responses to the survey. Opportunities were identified from actions that the potential to mitigate adverse changes in stream flow and temperature, and where the feasibility for implementation may be highest. Three adaptation strategies that ranked high and were diverse included the following:
   • Restoration of riparian ecosystems
   • Adjusting water licensing and allocations
   • Improving fish passage – though this strategy could not be completed because the base data layer (i.e., model to predict probability of blockage due to road crossings, such as a culvert) was still experimental at the time, and not available for broader distribution and use. Other guidance on adaptation was drawn from the survey

Predictions of habitat suitability for freshwater fish were modelled to prioritize management and monitoring areas among future climate scenarios. For example, Chinook salmon (figure below) are predicted to have higher suitable habitat by the 2080s since many more watersheds are gained than lost in terms of their thermally suitability. However, the models predict warming in the lower reaches of important migration corridors, mainly the Horsefly, Quesnel, and Chilcotin Rivers, which might lead to concerns about thermal barriers as well. Similar predictions were also developed for bull trout, and Coho salmon.

The information on habitat vulnerability and adaptation information support the iterative development of adaptation strategies through identifying priority regions and be integrated in planning exercises (e.g., Cariboo-Chilcotin Land Use Plan).