Climate change and glacier retreat in salmon watersheds

Global air temperatures are projected to rise over the next century following the continued increase and amplification of greenhouse gas emissions, mainly due to human activity. This rise in air temperature will pose significant changes to the landscape, most notably glacier retreat. Salmon watersheds beheaded by glaciers will undergo drastic changes as ice melts from the landscape changing downstream river flow, water temperature, and channel morphology, and shifting nutrients and availability of prey resources. Broadly, my thesis provides insight on how the effects of climate change, particularly from glacier retreat, may present challenges and benefits to Pacific salmon. In chapter 2, I explore the ways in which glacier retreat impacts salmon habitat by reviewing and constructing a conceptual model that defines glacier retreat across four distinct phases, from a landscape blanketed by ice to complete deglaciation. I describe each of these pathways of impact and how they will affect Pacific salmon across the four phases. In chapter 3, I quantify how much new Pacific salmon habitat will be created by glacier retreat over the next century. I found that glacier retreat will create hot spots of future habitat gains within glacierized regions of western North America, while other areas will experience no habitat gain. In my fourth chapter, I assessed how water temperatures along an important Pacific salmon migratory river are associated with landscape features of tributary systems. I placed temperature loggers at all major tributary rivers and determined how they play a role in cooling a major salmon migratory corridor. Glacier and snowpack fed tributaries from larger watersheds cooled a major salmon migratory river more than other tributaries. Collectively, this thesis provides insight into how climate change and glacier retreat impact river systems and their salmon. This work illuminates the need for forward-looking conservation and management to aid in the protection and preservation of important and iconic species, such as Pacific salmon.