As climate change nudges weather in the eastern Cascades in extreme and volatile directions, forest managers in the region have a lot to juggle. Hotter, drier summers are contributing to bigger and more frequent wildfires. Meanwhile, warmer winters may cause the Cascades to lose 50% of its annual snowpack over the next 70 years. Mountain snow supplies the Yakima River Basin with 75% of its water supply, making it a crucial reservoir for both nature and agriculture . Less winter snow also leads to drier and more fire-prone forests in the summer.

To encourage fire resilience, forest managers use tried-and-true tools like controlled burning and the selective felling of trees to thin out the forest. Both methods remove fuel and help return forests to historical conditions 鈥� but less is known about their impact on snowpack.

To address this knowledge gap, a team of researchers at the 天美影视传媒 and The Nature Conservancy (TNC) embarked on an ambitious, multiyear study of snowpack along Cle Elum Ridge, an area of the eastern Cascades in the headwaters of the Yakima River Basin. The group experimentally thinned the forest to varying degrees in a roughly 150-acre area. Then, they measured the amount and duration of snowpack during the winter of 2023 and compared it to a previous winter before the forest treatment.听

The results were encouraging: Forest thinning efforts increased snowpack by 30% on north-facing slopes and by 16% on south-facing slopes. Thinning aided snowpack the most where it created a patchwork of gaps in the forest rather than a more even density; gaps of 4-16 meters in diameter seemed to be the 鈥渟weet spot鈥� for snow.听

The research points toward more refined forest management practices that can optimize for both wildfire resilience and snowpack.

in Frontiers in Forest and Global Change.

鈥淎t its core, this research shows that reducing wildfire risk and protecting water resources don鈥檛 have to be competing goals,鈥� said lead author , a postdoctoral researcher at the University of Alaska who completed this work as a UW doctoral student of civil and environmental engineering. 鈥淭hat鈥檚 genuinely good news for a place facing both growing wildfire threats and increasing water vulnerability. So much of the climate conversation focuses on loss, which makes findings like this especially meaningful.鈥�

Predicting snowpack in forested areas, especially those at higher altitudes, hinges on understanding how much snow reaches the ground and how much lands in the forest canopy. Snow on the ground is more likely to stick around through the season, whereas snow in the trees may either melt or sublimate back into water vapor. In either case, it wouldn鈥檛 add to the reservoir of water that melts in the spring and summer.听听

鈥淭rees intercept snow and so can reduce snowpack, but trees also shade snow and so can retain snowpack,鈥� said senior author , a UW professor of civil and environmental engineering. 鈥淭he dominant effect depends on winter temperatures, and the Cascade crest near Cle Elum is right on the border where the effect flips from trees decreasing snow to trees saving snow.鈥澨�

found that natural gaps in the forests of the eastern Cascades accumulated more snow. This, combined with other research, gave the team reason to hope for a positive connection between forest thinning and snowpack, though it wasn鈥檛 a sure thing. have found that open areas elsewhere in the Western U.S. saw reduced snowpack.

Thus, it was time for a direct 鈥� and complex 鈥� study of managed forests.

Researchers picked Cle Elum Ridge for the work, where TNC鈥檚 forest managers were planning thinning treatments to improve forest health and wildfire resiliency. The orientation of the ridge allowed them to compare north- and south-facing slopes 鈥� southern slopes in the region see more sunshine and less snow retention on average. From October 2021 to September 2022, the researchers worked with TNC鈥檚 forest managers and local contract loggers to remove trees on both slopes in a gradient, from no thinning to extensive. The team also set up time-lapse cameras at several strategic points to measure snow depth over time.

Then, they waited for snow to fall.

By March 2023, the area was close to its peak snowpack, and the team returned with staff and equipment from the UW (RAPID). The RAPID crew flew a specialized drone that generated a detailed 3D map of the study area using a laser-mapping technology called lidar.听

By comparing the new 3D map and timelapse imagery to lidar data captured before the forest treatment, the team was finally ready to calculate two things: the change to the forest structure, and its effect on the snowpack.

Across the whole study area, the team found that thinning helped the forest recover 12.3 acre-feet (or about four million gallons) of water in the form of snow per 100 acres on north-facing slopes, and 5.1 acre-feet (or about 1.5 million gallons) per 100 acres on south-facing slopes.听

As expected, areas where the thinning opened gaps in the canopy were most effective at restoring snow storage that had been previously lost to environmental degradation and climate change. Gaps of 4-16 meters in diameter seemed to retain the most snow, though there were few gaps larger than 16 meters to evaluate.

One surprising result: The way forest managers thin forests doesn鈥檛 reliably create gaps. Forest managers map out their reductions using the density of trunks in an area, not canopies, as their primary measurement.

鈥淚magine a group of 100 people all holding umbrellas in the rain,鈥� said co-author , director of the UW Climate Impacts Group. 鈥淭hey鈥檙e standing close enough together that their umbrellas overlap, so none of the rain hits the ground. If you remove 10 of the umbrellas randomly, you鈥檇 still have plenty of coverage overall. But, if you remove 10 umbrellas that are right next to one another, you create a gap in the umbrella 鈥榗anopy,鈥� and you get a 10% increase in the amount of rain that hits the ground.鈥�

That realization adds a nuance to the findings. It鈥檚 likely that forest thinning can benefit both wildfire and snowpack resilience at the same time, but only if managers keep canopy gaps in mind.听

鈥淥ne thing we all learned was that snow people and tree people speak different languages,鈥� Lumbrazo said. 鈥淒ifferent experts look at totally different variables to help them decide whether or not to cut down a single tree. So an important goal is to get everyone speaking the same language. And I think this paper is one step towards better communication.鈥�

Overall, the results suggest practical changes to forest management practices in the eastern Cascades. For example, managers might consider more tree-thinning on north-facing slopes, since snowpack gains may be greater there. With further research, these learnings may also extend to other regions in the Pacific Northwest.听

The work could also aid collaboration between forest managers and hydrologists at a time when the region needs all the water it can get.

鈥淎s we lose snowpack, everything becomes really squeezed,鈥� said co-author , a senior aquatic ecologist at TNC who earned her doctorate in aquatic and fishery sciences at the UW. 鈥淲e are currently in our third consecutive year of water restrictions in the Yakima River Basin, and are staring down one of the lowest snow years on record. However, our research shows that the treatments currently used for restoring fire resilient forests are compatible with the forest structure needed for supporting water security. And in a world where climate change is reducing water supplies and increasing wildfire severity, we are pleased to report that the same forest treatments can support both goals.鈥�

Co-authors include , a former UW graduate student of civil and environmental engineering; , a former UW undergraduate student of atmospheric and climate science; , a data processing specialist at the UW RAPID facility; and , director of Forest Conservation and Management at The Nature Conservancy.

This research was funded by The Washington Department of Natural Resources, The Nature Conservancy and the National Science Foundation.听

For more information, contact Lundquist at jdlund@uw.edu, Dickerson-Lange at dickers@uw.edu or Howe at emily.howe@tnc.org.听

The , adopted in 1994, helped quell mounting tensions between timber companies and environmentalists. It protected large swaths of old-growth forest in Washington, Oregon and California to preserve habitat for endangered species, including the and .

While the plan is largely considered a success, researchers and land managers have begun to question whether it adequately protects forests threatened by climate change. Wildfires of increasing strength and severity sweep through Northwest forests every year, both on the east side of the mountains where conditions are drier and in wet mossy western forests.

, researchers looked at more than 2,200 fires over several decades to evaluate how wildfire is impacting Northwest Forest Plan lands. They observed a steady uptick in area burned and severity of wildfire in both dry and moist protected forests during the study period.

Federal and state representatives have been in conversation about for several years now. A new iteration of the Northwest Forest Plan could lean on more active management, including intentional burning and Indigenous cultural burning, which involves strategically introducing fire to maintain ecosystem health.

UW News asked the study鈥檚 lead author, , a UW senior research scientist of environmental and forest sciences, what the new research means for the plan.

Why did you do this study?

Gina Cova: For several years now, people have talked about revisiting the Northwest Forest Plan to incorporate amendments that account for the effects of recent wildfires and climate change. Some of these conversations were inspired by executive orders emphasizing the importance of old-growth forest protections. Others followed new research documenting the effects of climate change across the region.

We鈥檝e seen more fire within the Northwest Forest Plan area, both in dry, fire-prone forests, but also in moist forests that we consider less likely to burn. Those events included a few really high-profile fires, such as the that burned close to 175,000 acres in western Oregon and raised questions about land management strategies in this era of climate change. We started to think about evaluating these past fires to inform plan amendments aimed at management strategies to sustain old forests across the region.

What were some of the key takeaways from the study?

GC: 听A broad theme is that these are dynamic landscapes and they need to be managed as such. We looked at the environmental factors driving burn severity for 2,200 different wildfires and studied the forest patterns resulting from those events. The effects of wildfire in some areas were surprising. For example, we found that high severity fire affected around 60% of pine-oak woodlands in federally protected reserves throughout the eastern Cascades and Klamath regions. These forests are adapted to frequent, low intensity fires. We know that they need fire, but the severity of these fires reflects a long history of fire exclusion 鈥� or lack of fire 鈥� across the landscape.

What do you mean by a lack of fire? Aren鈥檛 we supposed to stop wildfires?

GC: Because enacting changes to management strategies has been difficult to do in practice, parts of the Northwest Forest Plan inadvertently reinforced the idea of preserving a static forest condition. This approach is analogous to drawing a boundary around a forest to prevent disturbance. It is rooted in conservation ideas from the early and mid-20th century, but we know that disturbances 鈥斕齟specially fire 鈥� are important for forests. So, you get this kind of fire paradox where many of these forests need fire, but the longer they go without it the more devastating it ultimately becomes.

These frequent-fire forests 鈥� like pine-oak woodlands and dry mixed conifer forests 鈥� can ultimately fare better in a warmer climate, so it is really alarming to see how much dry forest cover we are losing to fire under current management strategies.

What about other forests? How can one plan account for both dry and moist forests?

GC: It鈥檚 going to require a bit of creativity, combined with place-based, local approaches. The past three and a half decades have been relatively quiet in terms of fire activity in moist forests west of the Cascade Mountains. However, over the past 10 years, we observed an increase in area burned and area burned at high severity, indicating more loss of forest cover. This trend reflects some of these big fire years that have occurred in the last decade.

It can be harder to predict future wildfire activity in moist forests. When fires do occur, our study documented several occasions where high severity fires affected entire forest reserves. This creates gaps in this network of old forest habitat the plan was designed to create. If recent wildfires have compromised that original goal, how might future management strategies need to adapt? This could look like adjusting the boundaries of existing forest reserves, implementing protections for forests outside of reserves or building flexibility into pre-and post-fire management strategies to protect forests.

How can we keep the plan current when conditions are changing so quickly?

GC: When you manage land with a focus on a single issue, or a limited set of issues, you鈥檙e going to run into problems. The plan accounted for the effects of wildfire as it was in 1994, but did not anticipate how wildfire would shift with climate change. We don鈥檛 necessarily need to know exactly what the landscape will look like in the future, but we need policies and management strategies that will allow us to adapt to changing and novel conditions.

We have pretty strong evidence that the next century will be warmer and bring more fire. Can we create a plan that incorporates adaptive management to anticipate some of these changes instead of just responding to them as they occur.

Co-authors include , a UW research scientist and , a UW research associate professor, both of environmental and forest sciences; Harold Zald of the USDA Forest Service, and of the Washington Conservation Science Institute.

This research was partially funded by the USDA Forest Service.

For more information, contact Cova at cova@uw.edu.

When uncontrolled wildfires moved from the foothills above Los Angeles into the densely populated urban areas below in January 2025, evacuation ensued and a thick layer of toxic smoke spread across the region. Air quality plummeted. Local hospitals braced for a surge,.听听

Research led by the 天美影视传媒 and Kaiser Permanente Southern California sheds new light on how the Los Angeles fires affected people鈥檚 health, and how people navigated the health care system during an emergency. In the rapid study, published , researchers analyzed the health records of 3.7 million Kaiser Permanente members of all ages living in the region. They found that health care visits did rise above normal levels, especially virtual services.听听

In the week after the fires ignited, Kaiser Permanente members made 42% more virtual visits for respiratory symptoms than expected. Those living near a burn zone or within Los Angeles County also made 44% and 40% more virtual cardiovascular visits, respectively, than expected.听

In-person outpatient visits for respiratory symptoms also increased substantially. Members who lived near a burn zone or within Los Angeles County made 27% and 31% more virtual cardiovascular visits, respectively, than expected.听

Extrapolating to all insured residents of the county, the researchers estimated an excess of 15,792 cardiovascular virtual visits, 18,489 respiratory virtual visits and 27,903 respiratory outpatient visits in the first week of the fires.听

The results suggest that people may rely more heavily on virtual health care during climate-related emergencies, and that providers should better prioritize virtual and telehealth services as they prepare for future crises.听

鈥淲e saw over 6,241 excess cardiorespiratory virtual visits in the week following the fire ignition. This represents a substantial increase in care,鈥� said, a UW associate professor of environmental and occupational health sciences and of epidemiology who led the research. 鈥淲hile the fires clearly impacted health, virtual care likely enhanced the ability of providers to meet the health care needs of people experiencing an ongoing climate disaster.鈥澨�

In collaboration with Kaiser Permanente Southern California, an integrated health care system with millions of members across the region, researchers analyzed health records of people who were highly or moderately exposed to wildfires. They defined high exposure as living within about 12 miles (20 kilometers) of a burn zone, and moderate exposure as living within Los Angeles County but farther than 12 miles during the time of the fires.听听

Researchers looked back three years to estimate how many health care visits to expect in the weeks following Jan. 7 鈥� the first day of the fires 鈥� under typical conditions. They then estimated how many people sought care in the first week of the fires, when smoke levels were highest, evacuations took place, and Los Angeles County public schools were closed.

In addition to the spike in cardiovascular and respiratory visits, researchers found a sharp increase in the number of visits for injuries and neuropsychiatric symptoms. On Jan. 7, outpatient injury visits were 18% higher than expected among highly exposed members, and virtual injury visits were 26% and 18% higher than expected among highly and moderately exposed groups, respectively. Among those same groups, outpatient neuropsychiatric visits rose 31% and 28% above expectations, respectively.

While both groups made significantly more visits than expected, proximity to the fires mattered. When researchers zoomed in on respiratory-related virtual visits, they found that minimally exposed members made 31% more visits, moderately exposed members made 36% more, and those living in highly exposed areas made 42% more.听听

鈥淲hile healthcare systems often plan to increase the number of hospital beds available or clinic staffing during an emergency, this work highlights the importance of considering virtual care capacity,鈥� said, a UW doctoral student of epidemiology and co-author on the study. 鈥淭his may be particularly true for climate disasters like wildfires, during which people are advised to stay indoors or when people must evacuate 鈥� motivating them to seek care online if at all possible. As climate disasters increase in frequency and intensity, it is essential that health care systems know how to prepare for a sudden and dramatic surge in health care utilization.鈥澨�

Other authors on this study are , and of Kaiser Permanente Southern California; of the University of California, Berkeley; of Kaiser Permanente Hawaii; and of Columbia University; and of the Scripps Institution of Oceanography at UC San Diego; and of the Scripps Institution and the University of Rennes in France.

This research was funded by the National Institute on Aging and the National Institute for Environmental Health Sciences.听

For more information or to reach the research team, contact Alden Woods at acwoods@uw.edu.