The Northwest Climate Adaptation Science Center (NW CASC) organizes an annual Deep Dive into an emerging climate risk. We convene researchers, practitioners and students to assess the state of knowledge and practice associated with managing that risk. Each Deep Dive aims to facilitate community development of an Actionable Science Agenda that outlines knowledge gaps and research needs and identifies opportunities to advance adaptation by linking science and practice.

Loss of Winter: Managing the Ecological Effects of Shorter and Warmer Winters in the Northwest

Northwest winters are increasingly starting later, ending earlier and exhibiting warmer temperatures with consequences for regional hydrology and ecology. Hydrological consequences include an increased proportion of precipitation falling as rain rather than snow, reduced snowpack, and altered timing of snowmelt and subsequent runoff volumes, streamflows and stream temperatures. Lesser or earlier snowmelt can also reduce availability and increase periods of high evaporative demand during non-winter seasons. These shifts in the timing and magnitude of winter temperature, precipitation, and hydrology can collectively be viewed as a loss of historical Northwest winter conditions (“loss of winter”), and have numerous ecological consequences including:

• reduced habitat quality and extent for cold- or snow-dependent species,
• expanded ranges and increased impacts of pests and pathogens,
• unfulfilled plant hardening and/or germination requirements, and
• behavioral changes and potential phenological mismatches altering the outcomes of interactions such as predation and competition.

These ecological consequences include risks to iconic and culturally important Northwest species such as salmon, moose and yellow-cedar, as well as the broader ecosystems within which they occur.

Despite growing documentation of the loss of winter in the Northwest, much remains unknown about its near- and long-term ecological impacts and options for managing them to reduce and adapt to negative effects on species and ecosystems. Scientists and natural resource managers require a greater understanding of potential ecological impacts as well as management and policy options for supporting the resilience of Northwest species and ecosystems facing loss of winter.

To help meet these needs, the Northwest Climate Adaptation Science Center’s 2026 Deep Dive will bring together a diverse group of scientists, managers and other relevant partners to co-create a regional synthesis describing the state of the science, management and human dimensions around the impacts of winter loss on species and ecosystems in the region. They will also identify key needs for addressing gaps in knowledge and capacity. Through this process, the Deep Dive aims to build the knowledge, capacity and communities of practice required to anticipate and respond to the ecological impacts of loss of winter on Northwest ecosystems.