Future Outlook

-->The future of salmon in the Pacific Northwest is an uncertain one, dependent on the compounding impacts of climate change, as well as the degree of human intervention to alleviate environmental stressors. Concrete projections of salmon performance and prevalence are rare, as the salmon life cycle depends on a variety of habitats and ecological parameters. Based on the work and expert knowledge of several University of Washington, Seattle researchers, however, the creation of a composite prediction is possible. Their knowledge provides a comprehensive view of the changes scientists expect to accompany continued climate change.

            The estuarine habitat available to Puget Sound salmon will shift with changes in patterns of sea level rise and sediment discharge. Areas of existing marshland, particularly in the southern end where elevation is on the low side of the gradient, will likely disappear as viable habitat due to accelerated sea level rise. The increased discharge of sediments from the Cascade Mountains, however, may create new wetland marshes in higher elevation areas with low, neutral, or even negative sea level rise. Such areas could adequately compensate for similar estuarine habitat loss, if identified as candidates for conservation projects and allowed to develop into natural marshes. On average, salmon that spend longer rearing in estuaries as juveniles have a higher spawner return rate, so the preservation and potential increase of estuarine habitat will help to bolster Puget Sound salmon numbers [33].

            Salmon species exist both as local populations and meta populations; thus, change and localized extinctions are normal, as processes of the meta population dynamics. Natural extinctions have historically occurred every few thousand years, followed then by recolonization events. Climate change is accelerating the rate of these extinctions, and will create conditions that may be too intolerable for recolonization [28]. Unfortunately, the Pacific Northwest is a region of high projected negative impact from climatic warming. In a mild temperate climate, even a small change in temperature has a profound impact on snow accumulation. Many PNW river systems are snowmelt driven, and will suffer from a lack of water in the summer as average annual temperatures increase, precipitation patterns shift, and snowpack decreases [32]. August and September are critical periods for salmon in respect to freshwater habitat, as these hottest and driest months coincide with the migration and spawning season. Additional water limitations will prove dangerous for salmon populations in areas that are already stressed by a lack of cold water in the late summer. Rivers of Eastern Washington, Eastern Oregon, and parts of Idaho will likely warm to the point of creating impassable thermal barriers. Even in Puget Sound, lowland rivers that already experience significant warming will pose a major problem in the future for salmon [29][30].

             Despite the overwhelming threats to salmon habitat viability in the PNW region, there are still areas where salmon are expected to thrive. Parts of the region that are presently high quality salmon habitat will most likely continue to harbor healthy salmon stocks well into the future. The climate of Western Washington, particularly that of the Olympic Peninsula and the coast, is very moderate and resists hot temperatures during the summer. Most of the watersheds that stem from the Olympic National Park are mostly protected, with at least their headwaters sheltered inside the park, and should be resilient to changing climate. In contrast, watersheds of the Columbia Basin are heavily impacted by irrigation withdrawals, groundwater depletions, and large dams. The extensive human influence on the Columbia Basin does provide a source of hope for these highly stressed habitats, however, thanks to the alleviation of climate impacts through mitigation efforts. Dam removal projects are already in progress to reopen habitat in the Columbia River tributaries, and more are proposed in similar areas throughout the PNW. In addition, restoration projects in Eastern Washington and Eastern Oregon are in the process of reviving water-depleted streams, while tribal reintroduction programs are focused on trapping and moving salmon into intact habitat above dams. Such continued efforts will reopen habitat to salmon and will potentially ease the projected temperature stress in these environments, reducing the negative impacts of climate change [29].

            Ultimately, some species and populations will perform better than others, due to intrinsic differences in life history traits. Stream-type populations, in general, are expected to decline in productivity because of their high dependence on streams for the juvenile stage, while ocean-type populations should remain robust, if not increasing in productivity [29]. As a whole, salmonids have been dramatically more productive globally in the last thirty years than ever before recorded. Coinciding with warming in the PNW, Alaska has experienced warming that has opened up additional suitable habitat to salmon in their northern range. While warmer conditions have caused decreases in salmon production in the southern end of their range, increases in temperature in Alaska and farther north have lifted thermal limitations that previously prevented salmon from utilizing extensive portions of their upper range. There, salmon grow faster with increases in temperature. Although the Arctic Ocean does not currently support salmon, it too has the potential to become salmon territory in the future as it warms and becomes free of ice for longer periods.  This upward trend in salmon production should continue with sustained climate change, as long as primary productivity and food availability also benefit from a warmer environment [32].

            Salmon are incredibly resilient organisms that have experience in adapting to and surviving a spectrum of climatic conditions. The preservation of genetic diversity allows salmon to respond to changes in their environment, and it is this biocomplexity that will allow them to colonize new habitat in their northern range as well as adapt to changing existing territory [31]. They only need to be given the opportunities to do so. It is then the responsibility of humans to provide salmon with the viable habitat required to rebound and thrive under shifting climatic conditions. Relieving anthropogenic pressures is necessary to combating climate change in the Pacific Northwest because salmon can only fight half the battle for themselves.