National Wildlife Federation Report: Climate Change Effects & Adaptation Approaches for Freshwater Ecosystems

With the growing number of scientific papers on climate change and continued interest among resource managers and conservationists to account for climate change in their work, there is a need to summarize climate change information for key geographies and ecosystems. In response to this need, National Wildlife Federation produced an extensive compilation of climate change effects and adaptation approaches specific to the freshwater aquatic and riparian ecosystems of the North Pacific Landscape Conservation Cooperative (NPLCC) geography.

Covering approximately 204,000 square miles, the NPLCC region extends from Kenai Peninsula in southcentral Alaska to Bodega Bay in northern California and stretches up to 150 miles inland to the crest of the Cascade Mountain Range and Coast Mountains. It is home to birds of conservation concern including the marbled murrelet, spotted owl and Queen Charlotte goshawk, iconic salmon, and a wide range of habitats crucial for the survival of other wildlife and for sustaining the Way of Life of many Tribes, First Nations, and Native Alaskans. Many of these species, habitats, and ecosystems are already experiencing the effects of a changing climate.

Temperature increases and altered precipitation patterns have resulted in reduced snowpack and summer streamflows, increased water temperature, and earlier snowmelt over the past century in most of the NPLCC region. These trends are projected to continue as temperatures rise further and more precipitation falls as rain than snow in most of the region, driving an increase in winter streamflow and flooding and further decreases in summer streamflow.
Lake levels and river inputs are likely to decline if increases in evapotranspiration are not offset by an equal or greater increase in precipitation. This may degrade nearshore habitat or isolate nearby wetlands, stressing species dependent on those systems
Warmer temperatures, reduced snowpack, and altered runoff timing is projected to cause drying of alpine ponds and wetlands. Habitat area and quality may be reduced for Cascades frog, northwestern salamander, long-toed salamander, garter snakes, and other species. However, loss of snowpack and glaciers may allow alpine vegetation to establish, leading to improved habitat conditions for some high-elevation species over time. Recently deglaciated habitats in coastal Alaska are also important to breeding Kittlitz’s murrelet, a bird species of concern.
Salmon, lamprey, and bull trout are at risk from increasing stream temperatures and altered streamflow patterns. Lamprey migrated up the Columbia River 13 days earlier from 1939 to 2007 in response to increased water temperature and decreased discharge. Bull trout are generally found in streams cooler than 60.8 °F in Washington, Oregon, and northwest California, but summer stream temperatures are projected to exceed 68 °F in many of these bull trout waters by 2100. Similarly, water temperatures exceeding the thermal maximum for salmon are projected for the Fraser River in British Columbia, the Lake Washington/Lake Union Ship Canal and Stillaguamish River in Washington, and the Tualatin River in Oregon in the 21^st century.
Invasive aquatic species found in the NPLCC region that appear to benefit from climate change include hydrilla, Eurasian watermilfoil, white waterlily, and reed canarygrass. Reed canarygrass, for example, is an aggressive invasive species expected to clog more streams in Alaska as waterways warm and lose ice.
Although uncertainty and gaps in knowledge exist, sufficient scientific information is available to plan for and address climate change impacts now.

Since climate change scenarios generally project a further increase in the atmospheric carbon dioxide (CO₂) concentration and an associated exacerbation of climate change effects, adaptation is emerging as an appropriate response to the unavoidable impacts of climate change. Adaptive actions such as incorporating climate projections into infrastructure planning, modifying invasive species protocols to account for climate change, and supporting wetlands and intact floodplains expected to persist over time can reduce a system‘s vulnerability and increase its capacity to be resilient to changing conditions. Ultimately, successful climate change adaptation will enhance the ability of natural and human communities to prepare for, accommodate, or cope with current and future climatic changes