Tree mortality during California’s drought

Last summer, after four years of extreme drought, more than 21 million trees died in California.

This figure is based on mortality surveys performed by the U.S. Forest Service, which every summer for the past 10 years has flown a small aircraft over most of the forested area of California and recorded the locations of dead trees. The mortality observed in 2015 was by far the worst ever recorded. Mortality was especially intense in the Southern Sierra Nevada, where, across many large landscapes, the majority of the conifers died.



Tree mortality in the Southern Sierra. Photos: U.S. Forest Service

I’ve been working with the U.S. Forest Service aerial mortality monitoring program and UC Davis and Yale colleagues Jens Stevens, Mason Earles, and Andrew Latimer to analyze the mortality patterns recorded by the Forest Service and to understand the factors that lead certain forests to suffer more during drought. The first step of the analysis was to take the set of polygons that the aerial observers drew around dead trees (here’s an example of those polygons from the Southern Sierra Foothills that you can view in Google Earth) and convert them into a regular grid in which each cell is assigned a value representing the number of dead trees observed inside it. Here’s the resulting grid for the mortality throughout the state in 2015, highlighting the serious situation in the southern Sierra:

View larger map

The map shows the mortality amount observed in each grid cell (adjusted proportionally for mortality patches that overlap multiple grid cells and/or only partially overlap a given grid cell). The map only includes grid cells that fell completely within the plane’s field of view (the Forest Service also reports their flight lines and approximate observation distance) in order to avoid bias in our subsequent analysis of mortality patterns–this explains the linear gaps in the mortality grid.

Our next step was to see how tree mortality rates changed with time, year after year, as the drought progressed. To do this, we converted the mortality survey data from each year into a grid the same way we did for the 2015 data. We can visualize the mortality over time as an animation:


The map makes it painfully clear that although there is always some amount of mortality each year, the mortality in 2015–particularly in the southern Sierra–is far greater than that observed during other years in recent history. It is interesting to note that 2105, the year in which mortality spiked, was the fourth year of extreme drought in the state. This observation highlights the fact that tree mortality can take several years to respond to drought. Such a delayed response is often observed in studies of drought stress, and the existence of this delayed response hints that we are likely to observe high mortality well into 2016 and potentially beyond, especially in Southern California, where the severe drought continues for a fifth year.

My colleagues and I have used the Forest Service aerial mortality survey data, combined with other sources of environmental data–including long-term climate–to evaluate the factors that predispose forests to experience high mortality during drought. Our analysis is currently in review at an academic journal–stay tuned for a description of what we found!

Fire at Fort McMurray: Talking About Fire in Real Time



Fort McMurray wildfire, May 2016

The 2016 fire season is well underway, and with it lots of talk about wildfire. Dominating the news right now is the Fort McMurray wildfire, which began May 1 and has now burned more than 565,000 acres (California’s Rim Fire was only 257,000 acres, and New York City is about 300,000 acres, for perspective ). About 90,000 people have been displaced. Though the cause of the ignition is still under investigation, unusually hot and dry conditions have contributed to the fire’s spread, and the fire is early in the season. Fort McMurray is a community not far from the Alberta Oil Sands (often referred to as the “Tar Sands”) and it has grown in response to available jobs in the oil industry.

It’s not surprising that many people have brought up climate change. There’s first the question of whether climate change has contributed to this particular fire, which is starting to become a familiar discussion. But the location of this particular fire really matters to this conversation. For one thing, boreal regions are more sensitive to climate change and fires at higher latitudes are likely to contribute to feedbacks that exacerbate warming. This is also an unusual case in that the victims of the fire are closely tied to the fossil fuel industry. It can be tempting to see a cruel irony there, even to blame the residents of these communities for their fate.

I’ve been following the fire for the past week, and the discussion surrounding it seems to come down to three main topics.

1) Has climate change helped make the Fort McMurray fire?

2) Has fire suppression helped make the Fort McMurray fire?

3) How should we talk about the Fort McMurray fire? Is it appropriate to discuss climate change at the same moment that people are losing their homes?

The first two topics are interesting, but since the title of this blog is “What We Talk About When We Talk About Fire,” I want to focus on #3, delving into the conversation about conversation about wildfire, that has been playing out between Canadian politicians, in the comment threads of online news articles, and in the Twittersphere. In the coming weeks, I hope to return to questions 1 and 2.

How should we talk about the Fort McMurray fire?

Last week, Canada’s Green Party Leader Elizabeth May stated:

“The fact that the forest fire season has arrived so early in northern Alberta is very likely a climate event – very likely related to extreme high temperatures and very low humidity, very low precipitation. . .I think our focus is always on the right now: to think for the firefighters, for first responders, for people who are losing their homes. It’s a disaster. But it’s a disaster that is very related to the global climate crisis.”

After her remarks, May faced backlash from those who felt that she was “exploiting the tragedy to advance a political agenda.” Prime Minister Justin Trudeau was among the critics, acknowledging the link to climate change but claiming that the conversation was not helpful right now:

“One thing we know is that with climate change there will be more extreme events, but, we know very well that placing a direct link between any fire or a flood and climate change goes a step beyond what is helpful and does not benefit a conversation we must have.”

Comments on articles about this exchange and tweets about the fire overall have reflected the divided opinions of May and Trudeau. Wading into internet comments has its dangers, but it can provide an angle on the conversation that you don’t get from polished articles. Here’s a sample:

Click to view slideshow.

I tend to agree with those who argue that we should talk about climate change now. As the Earth grows warmer and the real consequences of climate change—sea level rise, drought, storms, fires—start to become real, we will need to learn how to talk about climate-related crises in real time. Many people acknowledge the reality of climate change, but as a threat to national security (and as a campaign issue) it takes a backseat to terrorism and gun violence. People still illustrate climate change with pictures of polar bears, not with wildfire evacuees (a google image search brought me as many polar bears in the top 25 hits as images that even hinted at fires and hurricanes–are these really equivalent in scope?). We need to be clear that the consequences of climate change will affect real people and their homes, and we can’t do that by sticking to abstract concepts like changes in mean temperature or predicted feet of sea level rise divorced from real events.

Still, there are tactful and useful ways to talk in real time, and ways that are neither. Articles that jump to climate change generalities without a mention of the victims of the current fire will appear distasteful, especially so to those readers who view climate change as nothing more than politics. This ensures that such articles will only get shared among the educated elite who already agree that climate change is a major issue. Being labeled as an insensitive jerk is not the best way to get people to take your writing seriously.

So, many writers understand that during a time of crisis, one must at least acknowledge the victims before launching into science talk. The Nature Conservancy tweeted an article that was mostly about fire suppression and climate change—but the text of the tweet? “Our sympathies are with the people and firefighters in Fort McMurray.” I don’t doubt the sincerity of their sympathies, but this is also tactical—if you’re going to talk about these topics, make sure to mention upfront that you recognize the suffering in the present. It’s a sort of disclaimer—if you put the people of Fort McMurray up front, people know that you care, and you can move along to the big picture. It’s surely a better strategy than sticking a “by the way, we care!” at the end of your article. Still, the article TNC linked isn’t really about those people at all. It barely mentions them.

There seems to me to be a divide in the reporting on this fire, that reflects a divide I’ve seen in wildfire reporting in general. Articles fall into one of two types:

1) Human-focused incident reporting. Here we learn the size of the fire, how many houses it has consumed, how many firefighters are on the ground, how much it costs, and how many people have been evacuated. We might learn the cause of the ignition. There may be a few lines about fire weather, but the fire largely stands alone, and climate change is rarely mentioned. The main characters are individual homeowners, firefighters, and elected officials. The publications range from local news outlets to the international papers I cite below, and the audience for these stories is broad.

Examples: This one by the NYT, this one by the Guardian, this one by the BBC

2) Bigger picture science section reporting. The articles usually start with a particular fire in a particular place, but the article quickly moves on. We get a briefing on how hot temperatures and dry conditions created conditions that contributed to fire spread. Quotes from researchers abound. We probably hear about fire suppression, bark beetles, or drought. We hear about how this will be the new normal. The main characters in these stories are scientists, not evacuees of burned towns. Indeed, most of the characters are scientists in the United States who do not actually study the Canadian boreal forest at all–I think I’ve seen more fire scientists from Arizona quoted than those from Alberta. They broaden the scope so far that the story becomes about fire in the Western US, not Alberta. These articles tend to be published in major news outlets or environment-related blogs (like this one!), and I suspect the audience is much narrower and more highly educated than the one for type 1 articles.

Examples: This article by the NYT, this one from Time, this one from Climate Central, this one by the Christian Science Monitor

Some articles are in between categories, like this article about Justin Trudeau’s remarksthis blog post by Christopher Lyon, or this nice essay by The New Yorker. But these still tend toward one of the categories. For the most part, it’s very easy to sort articles into the two categories, and I don’t think I saw a single article that interviewed an evacuee and also mentioned climate change.

Often, these two kinds of articles are separated both in space and time. But for the biggest fires, ones that attract international attention, we sometimes see both articles at the same time, leading to the claims of insensitivity cited above.

Why do we see such a divide? Is there another way? Should there be?

I suspect we see this divide because newspapers have sections and journalists have their specialties, where science writing is separated from incident reports. News outlets cater to their audiences as well. But I do think there could be another way and that there should be. Here are just a few ways I suggest to bridge the divide.

  1. Try to interview locals affected by the incident AND scientists for the same story.
  2. Keep the science local–find someone who actually studies fire in Alberta to comment on a fire in Alberta, rather than resorting to a fire ecologist who studies a totally different system.
  3. If your story is people-focused, actually use the words “climate change” rather than alluding to hot and dry conditions.

Any ideas from the audience?

It may be difficult to put this into practice–journalism has its conventions and readers have their biases. But it’s time for science to escape the Science Section if we want people to truly understand its relevance to their lives.



In the Black & Green at Stebbins Reserve

Note to local readers: Stebbins is presently still CLOSED to the public and is expected to reopen in early May. Please respect the closure and allow the ecosystem some time to recover. In the interim you can visit via a guided walk or as trail crew–see here for more information.

I have written a couple of times now about last summer’s fire at Stebbins Cold Canyon Reserve. It’s not a fire that you would have heard about on national news. It wasn’t very big, and it didn’t cause a lot of infrastructure damage. But I’ve been very interested in this particular fire, because it’s local. I can drive to the burn site from my house in about 30 minutes. In fact, I can take a quick turn off the street where I live and can then drive all the way to Stebbins on the same road. When the fire was burning, I watched the smoke sit heavy on the horizon from my front yard, and I watched ash fall from the sky like summertime snowflakes. Stebbins is a place where I and my fellow residents of Davis go hiking on weekends; it’s where I took a visiting prospective student to give her a taste of California ecosystems; it’s where my colleagues and I built a new citizen science program over the last few years. Stebbins has become one of “my places,” along with the reservation behind my family’s house in New Jersey, my island scout camp in the Adirondacks, Lake Michigan, and others.

In environmental education and related fields, we talk about one’s “sense of place.” Your sense of place includes your knowledge of a landscape, ecological or otherwise, how you fit into it, and your experiences there. I am interested in the fire at Stebbins because it is a major change in a landscape for which myself and many people around me have a sense of place. Not only has the color and composition of this landscape changed since the fire, but so has the way we interact with and experience this place.

I have visited Stebbins now three times since the fire: August 2015, November 2015, and February 2016, each time with a different group of people. Here is what I’ve observed so far:


Visit 1: August 2015 (just 2 fire ecologists)

My first visit was about a month after the fire. I stopped by with a friend who has worked on the CPP-Stebbins citizen science project on the way to do some fieldwork for my dissertation research, just up the road. We were two fire ecologists, and we were excited to be there. The most striking thing was how the landscape had opened. I could suddenly see hillsides stretching up high to both sides, and out beyond the trail. Before, trees and dense shrubs blocked that view. Most trees still stood as they always had, but many shrubs were skeletons. We saw crisp blackened leaves still hanging on the trees and ash covering the ground. The bulletin board near the entrance had become a window, and fiberglass posts marking phenology trail plants had exploded–proving that they were, indeed, made of fibers. And amidst the brown and black and grey, even in the dry heat of California summer only a month post-fire–during a drought no less–was green. Green sprouts on a hillside of black soil, green sprouts at the base of trees, and green sprouts from the branches of a California buckeye! The buckeye wasn’t supposed to have any leaves at all in the summertime! We poked at resprouts and talked fire ecology until we reached a point where the trail was covered in debris, and we headed home.

Visit 2: November 2015 (citizen scientists)

In November, I put together a visit for the volunteers for our citizen science project, the California Phenology Project at Stebbins. These volunteers had been taking data on the timing of leafing out, flowering, and fruiting for a year before the fire, and they were eager to visit. We had a group of about 15. Our mission was to see how the reserve had changed, to take an informal inventory of the plants that they had monitored, and brainstorm how we might begin to do citizen science again post-fire. Though we’d had rain at this point, the landscape didn’t look too different than it had in August. The green sprouts were taller. Ladybugs had taken up residence in the remains of a shrub.

But this time, I got to watch a bunch of people who had developed a very strong sense of place in this landscape see how the place had changed. I had adopted Stebbins as my own over the past couple of years, but I didn’t really visit all that often. Our volunteers were out there every month, or every couple of weeks. They had a routine. They observed their plants closely. They knew them well. I had been concerned that we’d need to use GPS data to find the plants that they’d monitored, but I needn’t have worried. I watched with amazement as the volunteers identified the location of nearly every plant–chatting amongst themselves, “No, that toyon was definitely by this rock here” or “This is where one of the monkeyflowers was, I’m sure of it.” In the end, we located all of the plants except a few monkeyflowers, which would have had the least protection of any of the plants during a fire. For the volunteers, they not only saw the broad landscape change, but they could pick out changes to individual plants.

Visit 3: February 2016 (fire ecology students)

My most recent visit was less than two weeks ago, a little more than 6 months post-fire. I tagged along on the class field trip for UC Davis’s fire ecology course. It was obvious from the moment we got there that there had been big changes: there was lots of green. The shrub skeletons remained, but grass and moss had filled in between them on many hillsides. California poppies colored some slopes yellow-green. We paused every hundred feet or so to get the name of another wildflower. I saw tiny, half-inch seedlings of the Ceanothus species that I am germinating (with fake fire!) in the lab. Not all was green–some areas are still pretty black and brown. But other places are brighter green than I’ve ever seen them. One hillside was covered in moss so colorful and soft that a student and I agreed that we should like to take a nap right there, on the new green carpet that had sprouted under the burned out chamise. It was so cool that I went home and googled “fire moss regeneration,” but I didn’t find much–just papers about fires in peat.

Over the course of three visits, I’ve built on my sense of place at Stebbins, watchning how it has grown and changed so far. I’ve seen changes to the landscape view–the macro scale–and to branches of individual trees–the micro scale. And I’ve watched other people build their sense of place, too.

I’ve been in several post-fire landscapes before–including several on a much larger, more newsworthy scale. I remember seeing the effects of the Yellowstone Fires in about 1998 with my family, ten years after those huge fires shaped national perceptions of wildfire on the landscape. More recently, I had the opportunity to explore high-severity areas of the Rim Fire in Yosemite. I learned a lot in those landscapes. But there is something truly special about watching a fire change a landscape that you know well, that you can visit by driving down the street for half an hour. That’s what a sense of place is all about.


A Tale of Two Fires

Note: Stay tuned for a long overdue Wildfire Media Roundup as well as a report from my visit to the Association for Fire Ecology’s Fire Congress in San Antonio. In the meantime, here is a piece I wrote for a campus publication recently about fire and outreach. 

I’d been keeping an eye on the Cal Fire maps all summer, looking for fires in the vicinity of my field sites. It was a hot, dry summer, and I was setting up seed traps in dense, flammable chaparral stands up and down the state. But I didn’t find out about the first fire near one of my sites from the internet. It was the blanket of smoke that sat on the horizon, visible from my front yard in West Davis. This was the 8,051-acre Wragg Fire, which started in late July 2015 and burned through Stebbins Cold Canyon Reserve. A week later, the 69,438-acre Rocky Fire burned large sections of Lake County, including much of McLaughlin Reserve. Not long afterward, the Jerusalem Fire burned up to the edge of the Rocky Fire, forming one large burn area.

I’ve been thinking a lot about these two fire events recently (considering the Rocky and Jerusalem Fires together)—how their similarities and differences reflect the complexity involved in fire ecology and management at large. Both reserves are dominated by chaparral and oak woodland. Both have steeply sloped terrain and lie within California’s Northern Coast Ranges. The fires would have burned hot and spread quickly through shrublands. Both places are characterized by vegetation that is well-adapted to fire and will likely recover without much difficulty or prodding. And though both reserves are intended for research and teaching, they sit within broader landscapes and communities. It is this last part that reveals why these fires are different. Though my own field sites were unaffected by the reserve fires, I have been involved with two reserve-based outreach programs over the past few years: the California Phenology Project at Stebbins, a citizen science program, and the Kids Into Discovering Science program for 5th grade students in Lake County schools. Both programs rely heavily on one of the reserves that burned, and both would be affected to some extent by the changed landscape in those reserves.

Though Stebbins is a UC Reserve, it is mostly used as a local hiking spot. It is part of our home, broadly speaking, but not many people live in the area affected by the Wragg Fire. The Wragg Fire caused little to no damage to infrastructure or human life. When our citizen science volunteers headed out to explore the reserve post-fire, the atmosphere was largely one of excitement: look at how this place we have been observing has changed! At Stebbins, we are free to think about fire as an ecological force, to enjoy the wildflowers, to use the opportunity to educate people about fire ecology. Our volunteers are also a self-selecting bunch—mostly adults, with strong backgrounds in science.

Talking to the Lake County kids about the Rocky and Jerusalem Fires this coming winter will be a very different story. Despite the similar landscapes, these fires were different from the Wragg Fire in important ways: 49 residences were destroyed in the two fires that burned McLaughlin, and the nearby Valley Fire destroyed over a thousand structures. These fires occurred on or quite close to the landscapes where many of these kids live. For them, wildfire doesn’t mean chamise skeletons and wildflowers. It means danger, evacuation, expensive repairs, and people displaced from their homes.

The narratives we can pull from my descriptions of these two fire events are the same two stories that are often told about fire in the media. Most often, we see the danger narrative from the Lake County fires. Numbers dominate the headlines: evacuees, firefighters, structures destroyed. Then, months or years later, we might see a story with the ecology narrative, usually a story about regeneration on the burned landscape. Rarely are these narratives put together. Yet so much of our modern understanding of fire science lies at the junction of the human story and the ecology story—climate change, fire management, invasive species, erosion—these are ecological issues and human issues.

As the CPP Stebbins at Kids Into Discovering Science programs continue into their post-fire lives, we’ll need to consider how we talk about wildfire. The fires at the two reserves are different. The audiences are different. Should the narratives we provide as teachers be different, too? Or is there a way to bridge the gap, and discuss what it means to live in a fire-prone ecosystem? The UC Reserves are places for both ecological research and for teaching, and the fires of 2015 will serve as a case study for both.

Wildfire Media Roundup #2, 11/12

Over the past two weeks, there have been a wide range of interesting fire articles. The articles below, taken as a group, are impressive in scope: from California to Indonesia, from fire science in a lab to restoration in the field, from serious investigation to dark comedy. Some of the news sites are small and local; others have international readership. The writers and their interviewees lament the loss of trees and homes, marvel at the way fire moves through vegetation, and take action to shape their local landscapes. Sometimes it is easy to think fire is only one thing–a fire in the hills of a California that destroys homes. But there are so many perspectives to consider in the study of fire. Here are a just a few:

International news focus on fires in Indonesia: until very recently, mentions of fire this year in the newspapers with national and international readership were almost exclusively about wildfires in the western US, mostly in California. However, as it’s cooled and begun to rain in California, a number of newspapers have shifted focus to Indonesia, a region not widely known for forest fires. All of a sudden, the Indonesian fires have become the subject of a wide array of articles, from this FAQ from the Guardian, to a human health-focused piece from the Economist, to a wildlife-focused one in the New York Times viagra prise.

But the American west still looms large in any media roundup. Now that the ashes have cooled from the big fires of late summer, people are taking stock of the effects of fire and looking forward to the future. In this article about the Butte Fire, locals lament the destruction of not only human structures but also the forest and discuss erosion control heading into a rainy winter. In some ways, it takes the opposite point of view of an article I linked last time, which marveled at forest resilience and discussed the value of large wildfires. Both articles present an opinion on how we should perceive wildfire, even though neither article looks much like an op-ed.

Next up–three articles of the focused more on the fire research side of things: a discussion of erosion and wildfire, a tour of the exciting happenings at the Riverside Fire Lab, and a study of fire dynamics in the wildland-urban interface (WUI). In these types of articles, researchers are the main characters. It’s about the fire research itself, and less about a specific fire event. The researchers clearly care about fire-prone landscapes and the people who live there, but they focus less on whether big fires are good or bad.

Finally, one of my favorite pieces of fire media yet: an article from the humor site The Onion–it takes themes from fire ecology and applies them in a ridiculous and wonderful fashion to a completely unrelated issue.