Ecosystems, and the wide range of services they provide to all species, including humans, are threatened by climate change in multiple ways. Climate change is already affecting the lower Columbia Estuary and is predicted to have profound impacts in the future. Some of the predicted changes that are expected to result in significant impacts to the fish and wildlife in the estuary are described below. More information about climate change causes and effects, both regionally and globally, is available from the US Global Change Research Program's 3rd and 4th National Climate Assessment reports, released in 2014 and 2018.
Streamflow and Flow Timing
According to the 2014 Report, since around 1950 the average snowpack on April 1 in the Cascade Mountains decreased about 20%, spring snowmelt occurred 0–30 days earlier depending on location, late winter/early spring streamflow increases ranged from 0–20%, and summer flow decreased 0–15% in the Pacific Northwest. By 2050, snowmelt is projected to shift three to four weeks earlier than the 20th century average, and summer flows are projected to be substantially lower.
Reduced summer flows, combined with increased water temperatures and increased demand from multiple users, will pose significant challenges for maintaining in-stream flow targets that ensure survival of Columbia River salmonids. During winter months, when more precipitation is expected to fall as rain instead of snow, increased flows may lead to increased flooding and erosion concerns. Shifts in flow timing can also adversely impact agriculture, and in particular irrigated crops that rely on groundwater and/or reservoir storage with limited capacity.
While the 2014 Report is uncertain about the overall change in precipitation amounts, it does point to an expected sharp decrease in summertime precipitation, of as much as 30% by the end of the century. Coupled with an already dry summer climate, this could have profound implications for the types of vegetation that will dominate in the future.
Extreme winter precipitation events which are expected to result from climate change may lead to more severe flooding and risk to infrastructure, and decreased water quality as more sediment and pollutants become mobilized. Increased sediment mobility and flows resulting from these events can in turn bury salmonid eggs and reduce salmonid survival.
A shift in precipitation towards increased rain and decreased snow is expected as average atmospheric temperatures continue to increase. This will result in reduced snowpack in many areas, which will impact the timing and magnitude of river flows as snows melt. It may also exacerbate water temperature increases, and change the quantity and quality of spawning habitat for various salmonid species that utilize snowmelt driven streams.
Summertime water temperatures in the mainstem Columbia River have been rising for decades, and will continue to rise as climate change continues. As shown by the US Forest Service's NorWeST Stream Temperature Model, rivers and streams throughout the Northwest are similarly threatened.
Increased water temperatures resulting from climate change will impact the estuary ecosystem in many ways. Salmonid species, all of which rely on cold water and become physically and metabolically stressed when exposed to water above certain temperatures, are directly threatened. Even today, mainstem Columbia River temperatures regularly exceed these thresholds for several weeks during the summer. The situation is expected to worsen as temperatures, as well as the duration of time that fish are exposed to lethal temperatures, continue to increase. According to the 2018 report, 'projections for increased stream temperature indicate a 22% reduction in salmon habitat in Washington by late century under a high emissions future.' Increased water temperature is also expected to reduce other aspects of water quality. Warmer temperatures decrease dissolved oxygen content, which is vital to the survival of aquatic organisms, and promote harmful algal blooms such as cyanobacteria, which have already become more prevalent in recent years. Finally, habitat for non-native, warm-water species will increase, increasing competition with, and predation on, native cold-water species.
Sea Level Rise
According to the Washington Coastal Resiliency Project's 2018 Sea Level Rise Assessment, sea level is likely to rise from between 0.2 and 2.0 feet by 2100 at the mouth of the Columbia River, depending on what emission's scenario unfolds. Sea level rise presents several risks to coastal communities, through accelerated erosion and increased flooding from tides and storm surge or wind-driven events. All of these can put infrastructure at greater risk. As stated in the 2018 National Climate Assessment report: 'As the pace and extent of coastal flooding and erosion accelerate, climate change impacts along our coasts are exacerbating preexisting social inequities, as communities face difficult decisions about determining who will pay for current impacts and future adaptation and mitigation strategies and if, how, or when to relocate.'
A potentially important ecological threat from sea-level rise in the estuary is the loss of wetlands habitat due to increased floodplain inundation. With nearly 80% of the estuary's historical wetlands already lost to development and other human impacts, knowing how much more will be lost due to climate change, and how much of that additional loss may be potentially offset by wetlands formation elsewhere, is a critical piece of information for estuarine ecosystem management.
What is Climate Resilience?
As described by the Center for Climate and and Energy Solutions, 'Climate resilience is the ability to anticipate, prepare for, and respond to hazardous events, trends or disturbances related to climate. Improving climate resilience involves assessing how climate change will create new, or alter current, climate-related risks, and taking better steps to cope with these risks.'
The Estuary Partnership is working to comprehensively incorporate climate resiliency and climate adaptation planning into its work wherever possible. We are assessing potential climate-related risks to the Estuary's ecosystems and communities it supports. We are working to revise guidelines for habitat restoration projects to ensure that projects being constructed today will continue to provide ecological benefits under future climate conditions. We are thinking about new restoration techniques and strategies to help alleviate identified climate risks, such as cold-water enhancement and living shorelines. As an organization devoted to diversity and equity, we are thinking about the ways in which climate change may disproportionately affect different communities and populations in our study area, and what we can do to address those.
Below are a few examples of how the Estuary Partnership is incorporating climate change, and climate resiliency, into our everyday work.