Range-wide life-history diversity and climate exposure in Chinook salmon

Climate change risk for migratory species is intertwined with their life-history diversity. Here I quantify climate risk, exposure, and phenological adaptive capacity in Chinook salmon during their spawning migrations for populations from across their North American range. First, I assessed how migration timing varies with watershed characteristics. Populations with longer migration distances and from higher elevations entered freshwater earlier. Second, I quantified climate exposure and risk by linking migration timing data to recent (1990s) and future (2040s) water temperatures. Nearly a quarter of populations will be exposed to future temperatures above thermally stressful thresholds. Third, I assessed the rate and direction of phenological shifts that would enable Chinook to adapt to climate warming. Spring populations would need to shift earlier, while fall populations would need to shift later. Broadly, my thesis highlights that climate exposure, risk and adaptive capacity are structured by phenology and latitude in a diverse migratory species.