Claim: Wildfires increase winter snowpack — but that isn’t necessarily a good thing

Study shows important potential implications for watershed hydrology

Deep in the Tushar mountains, some three hours south of Brigham Young University’s campus in Utah, Ph.D. student Jordan Maxwell and two other students found themselves in deep snow, both literally and figuratively.

It was December 2014 and the students had just started field work under the tutelage of BYU forest ecologist Sam St. Clair for research on the impact of wildfires on snowpack levels. Unfortunately, the snowmobiles they’d been using could go no further and there were still dozens of measurements they needed to take.

“So, we put on our skis and got to work,” Maxwell said.

The students would go on to log between 15 and 20 miles of back-country skiing each day in the field, measuring snow depth levels and snow water equivalency at 30 sampling spots within the footprint of the Twitchell Canyon Fire, a 2010 mega-fire that consumed 45,000 acres and was the largest active wildfire in the United States at the time.

The team also measured the presence, height and diameter of trees at each location and whether or not those trees were killed by the fire. After crunching the data, collected over that winter and the next, they found pretty impressive numbers: there was an 85% greater snow depth in areas that burned completely compared to areas that didn’t burn at all.

“Fires mean more snow into the system initially because of reduced trees that usually block and hold the snow temporarily on branches,” said St. Clair, a professor of plant and wildlife sciences. “It’s a really good outcome for north-facing slopes where the snowpack will hold in the shade, but If you’ve got a south-facing (sun-exposed) aspect with a deep snowpack and a rapid spring melt, now there is a higher chance of erosion, loss of nutrients and potential of flooding for downstream communities. The larger and more severe the wildfire, the increased flood potential for valleys.”

The research also revealed a 15% increase in snow-water equivalent — the amount of water contained within the snowpack — for every 20% increase in tree mortality in the burned areas.

The findings, recently published in Environmental Research Letters, represent the first study to examine the effects of burn severity on snow accumulation and water equivalence using direct measures. The researchers believe the study has considerable implications for water forecasting, especially given that snow-water resources from mountain watersheds provide fresh water for over 20% of the global human population and more than 65% of Utah’s water resources.

According to St. Clair, the new data helps paint a more complete picture on water security. To estimate future water resources, he said hydrologists should not only consider topography, aspect (north vs. south facing slopes) and how wet or dry a winter is, they also need to account for the increasing number and severity of wildfires and burn potential to properly assess the risks for flooding and drought.

“Wildfire regimes are changing forest ecosystems, and now we know they’re impacting water hydrology too,” St. Clair said. “This is our future — increased fired due to climate change. As a fire ecologist, this research is now in the center of what everyone cares about.”

Added Maxwell: “This project was impactful in the scientific community because it shows that not only an increase in the number of fires or in the area they burn, but also the severity of the fire, may have a large effect on the amount and quality of water that’s available for us to use. As climate anomalies become more frequent, we have seen and will likely continue to see more severe fires.”

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Press release from BRIGHAM YOUNG UNIVERSITY

The paper: https://iopscience.iop.org/article/10.1088/1748-9326/ab5de8

Snowpack properties vary in response to burn severity gradients in montane forests

Jordan Maxwell and Samuel B St Clair

Abstract

Wildfires are altering ecosystems globally as they change in frequency, size, and severity. As wildfires change vegetation structure, they also alter moisture inputs and energy fluxes which influence snowpack and hydrology. In unburned forests, snow has been shown to accumulate more in small clearings or in stands with low to moderate forest densities. Here we investigate whether peak snowpack varies with burn severity or percent overstory tree mortality post-fire in a mid-latitude, subalpine forest. We found that peak snowpack across the burn severity gradients increased 15% in snow-water equivalence (SWE) and 17% in depth for every 20% increase in overstory tree mortality due to burn severity. Snowpack quantity varied greatly between the two winter seasons sampled in this study with 114% more snow in 2016 versus 2015, yet the effect of burn severity on snowpack remained consistent. These data support previous studies showing increases in peak snow depth and SWE in burned forests but for the first time provides novel insights into how snow depth and SWE change as a function of burn severity. We conclude that changes not only in the frequency and size of wildfires, but also in the severity, can alter peak snow depth and SWE, with important potential implications for watershed hydrology.

Full paper (open source): https://iopscience.iop.org/article/10.1088/1748-9326/ab5de8/pdf

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39 thoughts on “Claim: Wildfires increase winter snowpack — but that isn’t necessarily a good thing

  1. The horse and the cart come to mind. There was 85% more snow in burnt areas. That means there was more precipitation in those areas. Likely then that there always was more precipitation in those areas also before any fire. Therefore more vegetation. Therefore bigger fires when the time comes than in places where average precipitation is low. Hence now more snow in burnt places.

    • It was not that there was more snow falling in the burnt areas, but more snow accumulation. Trees, especially conifers, intercept a lot of falling snow before it hits the ground. On sunny days, even when very cold, a good portion of that gets sublimated back into the atmosphere. Fewer trees means more snow directly to the ground.

      This is a well known effect – for example deer overwintering yards are usually in areas of thick conifer, due in part to the reduced snow accumulation allowing them to move more freely and access feed.

      Alarmist rhetoric in the article aside, this is a nice piece if field work.

    • And without that “before” data, it is likely that they have found out nothing of merit, nothing that can be duplicated by future research. GIGO comes to mind.

  2. Interesting posting of the BYU research, Anthony. It appears that snow held up on tree branches undergoes more ablation than deeper pack snow. The H2O budget of the earth is three phases: liquid, solid, and gas. The process of ablation, skipping from solid to gas, also is a lot of the story about glacier mass loss. When you are working downslope from a receding glacier it is surprising how little melt-water runs down. Kudos to the BYU students for going into the field, working hard, and learning hands-on science.

    • Nothing beats a good bit of fieldwork! Natural observations Trump model variables very time 🙂

  3. Curiously, annual bushfires in Australia over an average of 50 million hectares per annum have never managed to increase snowpack anywhere in the country in 250 recorded years.

    • It seems that bushfires inhibit snowfall, but wildfires increase snowfall. The science is settled. If Oz would just refer to the fires as wildfires, the continent would turn white. In a warming world, linguists have a vital role to play.

    • hmm well the snowfields all had decent falls this yr
      and some spots did get fires pretty close recently
      soooo
      lets see if the burnt bits get better snow this winter, shall we?

      decent rains going from qld right along the east and middle of the burnt n droughted spots
      lets hope it swings west a bit and everyone gets some;-)

  4. “Wildfires are altering ecosystems globally as they change in frequency ….. etc etc.”

    What the researchers mean is that this has always happened, but they have only just found out about it and if somehow they can link it to AGW then more folk will pay attention to it and keep the gravy train going.

    But fair enouth that the information can be used by forecasters; although maybe the local farmers and foresters knew this already.

  5. I think you meant sublimation rather than ablation, Ron. It would make sense that it is a function of surface area. Many more surfaces on snow in tree branches, than the surface of an open field.

  6. “Wildfires are altering ecosystems globally”

    And they didn’t do that before AGW came along? AGW impact research suffers from the childish confirmation bias that all things bad have the hand of agw in it and research questions methodology are constructed to discover HOW agw is making things so much worse (not whether). This kind of thing now passes for science. The underlying motivation is a search for just how bad agw is. A good example is the australian bushfires (link below). AGW is beginning to look like a rise and fall of civilization thing.

    https://tambonthongchai.com/2020/02/02/tbgyozfire/

  7. Once again I need help.
    When someone mentions an article that blames some event that he’s been occurring naturally for 1000s of years, on climate change I need a response.
    I just can’t think of anything that won’t get me sacked.

    • I highly recommend you visit Tony Heller’s blog – realclimatescience.com

      He is a master at showing old newspapers and other contemporary reports that bust the “unprecedented “ meme. Great concise videos on many climate-change topics, perfect for sharing with alarmist friends and colleagues because Heller is no confrontational and matter of fact

  8. While living on the coast of northern Luzon in the Philippines there was a typhoon.
    The next day the beach had changed totally.
    Over the following years the beach has been reshaped back to something similar to before the typhoon.
    Just as the climate is changing naturally on all timescales so is the landscape.

    • “but If you’ve got a south-facing (sun-exposed) aspect with a deep snowpack and a rapid spring melt, now there is a higher chance of erosion, loss of nutrients and potential of flooding for downstream communities. The larger and more severe the wildfire, the increased flood potential for valleys.””

      =

      beach

  9. Odd that they don’t mention shade in the spring slowing melt … I would think that’s more important than holding some of the snow off the ground … Their wording suggests evergreen trees, but the abstract doesn’t say. How representative are their 30 points? It’s really small sample statistics at best. Overall it feels like an undergraduate research poster …

  10. Admire the energy they put into the study in the field – but their conclusions … never mind.

    Sure vegetation has influence on the local precipitation and weather. Take for example Kilimanjaro where they turned the surrounding forest in urban development, with the result that the mountain top saw lower temperatures and less precipitation, resulting in disappearing white on the summit.

  11. Wildfires and forests burning are the natural state.
    Active fire suppression by man is not.
    The burned forest will be fine.
    Building a community in a frest and then wondering why it burned down is exactly like wondering why there’s “lava in the living room” when you build downslope from a volcano.

    That’s all you need to know.

  12. “Wildfire regimes are changing forest ecosystems” this is a false statement. wildfires are a NORMAL part of forest ecosystems. These people are PhDs????

  13. I ski a lot. What I see is that snow on the tree branches falls off when temperature rises or is blown off in severe winds. It mostly ends up on the ground.
    I think that the falling snow is compacted when it lands. This results in a thinner but denser snow pack compared to open areas.

  14. this is neither new or novel. look to the proceedings of the western snow conference publicly on line for all kinds of studies over the past 80 plus years on the impact of vegetation on snow accumulation, distribution and ablation. in the long term measurement of snow, look at the decrease of snow accumulation due to changes in vegetation – this has often been mis-identified as climate change but in reality is more due to vegetation change. )specifically look up papers by Julander, et al. burn areas also change snow albedo for many years after the burn which accelerates snowmelt – think charred standing trees slowly releasing black carbon on snow – so more snow, faster melt. bottom line – if you go from an open meadow to an aspen stand, you will lose up to 20-25% of your snowpack. if you further go to a conifer mix, you will lose 40% or more compared to an open meadow. thanks to smokey bear, western forests have undergone the most dramatic change of species composition and density over the past 50 to 80 years. the colorado basin alone has lost 2.5 million acres of aspen to conifer encroachment. in a utah state university study they reported up to 42% less water availabilty under conifers than comparable aspens stands in a combination of both lost snow water equivalent and soil moisture – that is relates to a comparative of about 10 inches of water on an average basis. spread over 2.5 million acres that is the potential of 210,000 acre feet of runoff lost per inch which equates to 2.6 to 26% of the average inflow to lake powell. thanks smokey bear.

  15. “As climate anomalies become more frequent”.
    As the weather is never at nominal, climate anomalies cannot become more frequent. It is always at an anomalous position relative to its calculated typical climate

  16. The Twitchell Canyon Fire was NOT a global warming induced fire. It was a deliberate burn by agency policy.

    The Twitchell Canyon Fire began as a lightning strike near Manderfield Reservoir, Fishlake NF, Beaver Co., Utah on 07/20/2010. There was no initial attack by fire crews. Instead USFS functionaries declared the fire to be a Wildland Fire Used For Resource Benefit (WFU).

    The declaration was made without regard to the National Environmental Policy Act (NEPA). There was no Environmental Impact Statement (EIS) prepared and no NEPA process despite clear requirements of the law. There were no Section 7 consultations as required under the Endangered Species Act (ESA). There were no Section 107 consultations as required under the The National Historic Preservation Act (NHPA).

    Federal functionaries violated laws that are supposed to specifically govern the actions of Federal agencies. They did so with impunity and utter disregard for numerous laws.

    The fire burned unimpeded for 3 weeks with only a “monitoring” crew. That crew actually expanded the fire by doing “burnouts” with incendiary devices. By 08/14/10 the fire had grown to 4,128 acres, and the watershed of the Manderfield Reservoir had been incinerated. There were 28 people assigned to monitor the fire which was 0% contained. No fire plan had been prepared.

    Three days later the monitoring crew was expanded to ~200 personnel to hand-build fire trails, ostensibly to protect the adjacent historic Manderfield mining district. To that date an amazing $1,065,516 had been spent on monitoring.

    more to come…

  17. One week later on 08/26/10 the crews were withdrawn save for 20 “monitors” and a single engine crew. The fire was 4,508 acres and still 0% contained. Costs to date were $2,448,000.

    Then on 09/04/10 the wind came up. The fire grew 700 acres overnight, then 1,600 acres the next day and 1,900 acres the day after that. By the evening of 09/06/2010 the fire was 8,870 acres and personnel had expanded to 198 fire fighters.

    Yet no real effort was made to contain the fire. By 09/15/2010 the fire had grown to 17,891 acres and only 86 personnel assigned. Reports were made of

    “extreme fire behavior observed over entire fire area. Rapid rates of spread, flame lengths observed of over 200 feet, 1/2 mile spotting with large ash landing over five miles northeast of fire area. Fire moved in high rates of spread to the north and is currently posing significant threats to a Power Corridor parallelling [sic] I-70 and to I-70 itself.”

    The USFS also reported some self-incriminating news, indicating that they were burning the forest deliberately for specific purposes, without any regard for NEPA, ESA, NHPA, or any other laws.

    “The fire is being managed for multiple objectives, which included providing for the safety of the public and firefighters, to increase structural diversity in forest and shrubland ecosystems through use of fire, reducing fuels in a mosaic pattern to effectively manage future fires, and to manage the fire for a scenic vegetation mosaic effect in the Manderfield Reservoir viewshed.”

    more to come …

  18. By 09/18/2010 the fire had grown to 22,788 acres and 550 personnel were assigned. The Incident Command reported that they were working to protect

    “Bonneville Cutthroat Trout”, shown in block 27 of the 209, reflects a “genetically unique strand” of trout found in streams North of I-70. The protection of this trout is identified as an Incident Requirement in the WFDSS and was activated on 09/16/2010.”

    Note that they didn’t give a crap about Bonneville trout while they were incinerating the watershed for two months. The only reason they is brought up on this date was to hamper fire fighting efforts by precluding use of fire retardant.

    Red flags were issued for high winds and on 09/19/10 the fire blew up to 30,000 acres. A week later it was reported at 39,073 acres, and a week after that on 10/02/10 it was 44,966 acres. Costs to date were $16,025,257 and 530 personnel were assigned. By 10/05/10 it was raining and crews were withdrawn. Over $17,000,000 had been spent to Let It Burn.

    The Twitchell Canyon Fire was NOT a global warming fire. It was deliberate incineration by lawless Federal functionaries. When BYU forest ecologist Sam St. Clair blames “climate change” for the fire he was either misquoted or a lying fraudsack. Let It Burn remains the policy of the USFS and BLM. They are unconscionable arsonists of our public lands.

  19. – expanding forests in colder areas could actually increase the temperature of snow-covered regions,

    – increase atmospheric humidity falling out of the air as ice crystals building clouds dispersing sunrays energy.

    Hopefully studies + climate models can handle that properly.

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