From SMU (Southern Methodist University) comes this press release which really isn’t surprising. North America didn’t have a forest fire suppression program for the last 1400 years, so there wasn’t a fuel buildup issue like we have today, forest floors were cleansed naturally by non-catastrophic fires.
Ancient tree-ring records from southwest U.S. suggest today’s megafires are truly unusual
Unprecedented study relies on more than 1,500 years of tree-ring data and hundreds of years of fire-scar records gathered from Ponderosa Pine forests
Today’s mega forest fires of the southwestern U.S. are truly unusual and exceptional in the long-term record, suggests a new study that examined hundreds of years of ancient tree ring and fire data from two distinct climate periods.
Researchers constructed and analyzed a statistical model that encompassed 1,500 years of climate and fire patterns to test, in part, whether today’s dry, hot climate alone is causing the megafires that routinely destroy millions of acres of forest, according to study co-author and fire anthropologist Christopher I. Roos, Southern Methodist University, Dallas.
The researchers found that even when ancient climates varied from each other — one hotter and drier and the other cooler and wetter — the frequencies of year-to-year weather patterns that drive fire activity were similar.
The findings suggest that today’s megafires, at least in the southwestern U.S., are atypical, according to Roos and co-author Thomas W. Swetnam, the University of Arizona. Furthermore, the findings implicate as the cause not only modern climate change, but also human activity over the last century, the researchers said.
“The U.S. would not be experiencing massive large-canopy-killing crown fires today if human activities had not begun to suppress the low-severity surface fires that were so common more than a century ago,” said Roos, an assistant professor in the SMU Department of Anthropology.
Today’s extreme droughts caused by climate change probably would not cause megafires if not for a century of livestock grazing and firefighting, which have combined to create more dense forests with accumulated logs and other fuels that now make them more vulnerable than ever to extreme droughts. One answer to today’s megafires might be changes in fire management.
“If anything, what climate change reminds us is that it’s pretty urgent that we deal with the structural problems in the forests. The forests may be equipped to handle the climate change, but not in the condition that they’re currently in. They haven’t been in that condition before,” Roos said.
Roos and Swetnam, director of the University of Arizona Laboratory of Tree-Ring Research, published their findings in the scientific journal The Holocene.
Study combines fire-scar records and tree-ring data of U.S. southwest
This new study is based on a first-of-its-kind analysis that combined fire-scar records and tree-ring data for Ponderosa Pine forests in the southwest United States.
Earlier research by other scientists has looked at forest fire records spanning the years from 1600 to the mid-1800s — a climate period known as the Little Ice Age — to understand current forest fire behavior. Those studies have found that fires during the Little Ice Age occurred frequently in the grasses and downed needles on the surface of the forest floor, but stayed on the floor and didn’t burn into the canopies.
Critics dispute the relevance of the Little Ice Age, however, saying the climate then was cooler and wetter than the climate now. They say a better comparison is A.D. 800 to 1300, known as the Medieval Warm Period, when the climate was hotter and drier, like today’s.
Scientists who favor that comparison hypothesize that forest fires during the Medieval Warm Period probably were similar to today’s megafires and probably more destructive than during the Little Ice Age.
Tree rings and fire scars provide the evidence for moisture, drought and burn activity
Scientists rely on tree rings not only to calculate a tree’s age, but also to determine wet and dry weather patterns of moisture and drought. Similarly, scientists’ best evidence for fire activity is the scarring on tree rings that dates the occurrence of fires. While tree-ring data for climate are available for long time periods, annual forest fire records don’t yet exist for the Medieval Warm Period.
In response to the need for data, Roos and Swetnam tested the Medieval Warm Period hypothesis by calibrating a statistical model that combined 200 years of Little Ice Age fire-scar data and nearly 1,500 years of climate data derived from existing tree rings. With that they were able to predict what the annual fire activity would have been almost 1,500 years ago.
They discovered that the Medieval Warm Period was no different from the Little Ice Age in terms of what drives frequent low-severity surface fires: year-to-year moisture patterns.
“It’s true that global warming is increasing the magnitude of the droughts we’re facing, but droughts were even more severe during the Medieval Warm Period,” Roos said. “It turns out that what’s driving the frequency of surface fires is having a couple wet years that allow grasses to grow continuously across the forest floor and then a dry year in which they can burn. We found a really strong statistical relationship between two or more wet years followed by a dry year, which produced lots of fires.”
Modeling of tree-ring and fire-scar data can be applied to any locale
The research, “A 1416-year reconstruction of annual, multidecadal, and centennial variability in area burned for ponderosa pine forests of the southern Colorado Plateau region, Southwest USA,” was funded by the International Arid Lands Consortium.
“The best way to look at how fires may have varied — if climate were the only driver — is to do this type of modeling,” Roos said. “Our study is the first in the world to go this far back using this methodology. But this method can be used anyplace for which there is a fire-scar record.”
The study’s tree-ring-derived climate data are from the southern Colorado Plateau, a region that includes the world’s largest continuous stand of Ponderosa Pine stretching from Flagstaff, Ariz., into New Mexico. Large Ponderosa Pine forests have existed in the area for more than 10,000 years.
Fire-scar data for the region go back as far as the 1500s, but are most prevalent during the Little Ice Age period. Fire scientists have analyzed fire-scars from hundreds of trees from more than 100 locations across the Southwest. All fire-scar data are publically available through the International Multiproxy Paleofire Database, maintained by the federal National Oceanic and Atmospheric Administration’s paleoclimatology program.
Ancient fires were frequent, but didn’t burn the forest canopy
Fire scientists know that in ancient forests, frequent fires swept the forest floor, often sparked by lightning. Many of the fires were small, less than a few dozen acres. Other fires may have been quite large, covering tens of thousands of acres before being extinguished naturally. Fuel for the fires included grass, small trees, brush, bark, pine needles and fallen limbs on the ground.
“The fires cleaned up the understory, kept it very open, and made it resilient to climate changes because even if there was a really severe drought, there weren’t the big explosive fires that burn through the canopy because there were no fuels to take it up there,” Roos said. “The trees had adapted to frequent surface fires, and adult trees didn’t die from massive fire events because the fires burned on the surface and not in the canopy.”
Today’s huge canopy fires are the cumulative result of human activity
The ancient pattern of generally small, frequent fires changed by the late 1800s. The transcontinental railroad had pushed West, bringing farmers, ranchers, cattle and sheep. Those animals grazed the forest floor, consuming the grasses that fueled small fires but leaving small saplings and brush, which then grew up into dense, mature bushes and trees. In addition, the U.S. began to restrict the traditional land use of the region’s Native American communities, including confining them to reservations. This removed another source for frequent surface fires in the forests — burning by Native Americans for horticulture and hunting.
By the early 20th century, the U.S. Forest Service had been established, and fighting fires was a key part of the agency’s mission. Without continuous fuel, fires on the forest floor ceased.
“Many of our modern forests in central Arizona and New Mexico haven’t had a fire of any kind on them in 130 or 140 years,” Roos said. “That’s very different from the records of the ancient forests. The longest they would have gone without fires was 40 or 50 years, and even that length of time would have been exceptional.”
The research reported in The Holocene is the basis for a new four-year, $1.5 million grant from the National Science Foundation in which Roos and Swetnam are co-principal investigators. That project will examine how human activities have changed forests and forest fires over the past 1,000 years of Native American occupation, as well as the influence of droughts during the Medieval Warm Period and Little Ice Age in New Mexico’s Jemez Mountains. — Margaret Allen
SMU is a nationally ranked private university in Dallas founded 100 years ago. Today, SMU enrolls nearly 11,000 students who benefit from the academic opportunities and international reach of seven degree-granting schools. For more information see www.smuresearch.com.
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“Ancient tree-ring records from southwest U.S. suggest today’s megafires are truly unusual”
How many of today’s fires are started by the carelessness of people or even intentional started by people. I would imagine most ancient fires were started by lightning and not a gallon of gasoline and a Bic lighter. Also, once these ‘wild’ fires get started often it will encounter a house or a barn, etc. which seem to burn a lot hotter than the natural landscape. It is amazing when these are reported in the news how many are actually caused by humans, yet they are still referred to as ‘wild fires’.
In response to the need for data, Roos and Swetnam tested the Medieval Warm Period hypothesis by calibrating a statistical model that combined 200 years of Little Ice Age fire-scar data and nearly 1,500 years of climate data derived from existing tree rings. With that they were able to predict what the annual fire activity would have been almost 1,500 years ago.
Translates to:-
In the response to the need for data we made some on a PC.
Downhill rapidly from there.
I am from SW Louisiana. My grandfather and his brothers used to burn our land every single year. they raised sheep and pine trees and this was just part of growing up.
That generation is gone and there is precious little controlled burning now. However there are lots more raging fires.
It is amazing that it takes “scholars” with big degrees and tree ring studies to figure out what previous generations knew by intuition.
After living in Colorado for 40+ years, and hiked the mountains, forests and plains. Even during the “wet” years, there is virtually no precipitation from the end of May until the beginning of August, The live ponderosa pines drop moisture content to 10-15%, like dried wood. There is nothing to keep the ‘canopy’ from burning. Does a forest of 15-20′ trees even have a canopy? Looking out my window at the forest across my road, there is nothing that could be construed as a canopy.
The focus on forest fires is another example of a limited study. It’s true there wasn’t a fire suppression process in place in recent decades, but there was an extensive use of fire for hunting and defense by humans since they arrived in North America prior to arrival of Europeans.
A very good overview of these fires and the role of humans in causing them is provided in the Summer issue (Volume 60. No.3. 2000) of Fire Management. There is a very interesting graph showing offshore sediments and the occurrence of charcoal related to land based fires.
Limiting the study to forest fires is another problem with the study.
I recall an entry in the Hudson’s Bay Company journals for the 1790s that says the Indian’s report the whole of the Prairies are on fire. Grass fires were a major factor in the ecology of North America and undoubtedly spread into neighbouring forest regions. There is a famous painting by Paul Kane of a praise grass fire. The southern edge of the boreal forest is extending south partly because these fires are now suppressed. Communities like Carberry Manitoba installed municipal water supply primarily to fight grass fires that threatened their homes on a regular basis.
None of this is surprising because grasslands, variously called savanna, pampas, steppes, tundra, Prairies, and Great plains, cover a reported 13.8 percent of the land mass and are overlooked in recent climate studies.
http://earthtrends.wri.org/text/forests-grasslands-drylands/map-229.html
Koppen recognized them in his climate classification system but that was because he featured the role of precipitation in his B classification. Since then, with the IPCC focus on temperature, they have dropped out of the picture. I am not aware of any estimates of the input and output of CO2 from this significant source and sink, but then we didn’t start measuring them for the vast boreal forest until relatively recently and then in limited studies.
Wow – this is becoming a bit surreal. The link between fire severity and AFS (anthropogenic fire suppression) is VERY well known and has been for quite some time.
I wonder, exactly how much does a study like this receive in grant $? It seems anything can get funded based on tie-in to CAGW, but exactly how much $ are we talking about? If the money is available their will always be takers. A good feedback mechanism would be to require publicly funded grant recipients to publish the amount of the grant alongside the work. That will help the public decide if they are truly getting value for their tax dollars.
The percentage of wildland/forest fires started by human activity is stunning.
As just one example, a building contractor using a power tool on a jobsite started a 17,000 acre forest fire about 3 miles from my house. Power lines sparked a fire that ripped through a neighborhood not far from there and destroyed homes. A poor old guy put fireplace ashes out and started a huge wildland fire that destroyed homes. Huge fires, all human caused. Natural fires have been few and far between.
http://www.interfire.org/features/wildfires.asp
cotwome says:
May 18, 2012 at 7:04 am
From a standpoint of here in AZ, a very small portion of the fires are from human sources. However, the ones that you hear about and caused the most damage over the last few years are the result of carelessness and pyromaniacs. However, during a normal monsoon season, a multitude of fires are started from lightning strikes and are usually put out very quickly by the forest service. I have to disagree with your “a building burns hotter” statement since many fires in AZ do not even come close to structures, it is the excessive buildup of undergrowth that causes the fires to burn too hot allowing the flames to travel to the crown of the trees. Several individuals have already mentioned why we have more severe fires now than in the past and that has to do with the progressive/green mindset of forest maintenance which many for the forestry departments, particularly NAU, in AZ are fighting to reverse.
The Eastern US forests were different back then. Most of the trees in Appalachia, for example, were American chestnut; the “Redwood of the East”. These trees were absolutely huge and grew much taller than the trees that populate that area today. These trees grew rapidly and would reach an excess of 100 feet tall and commonly being over 8 feet in diameter were pretty hard to burn from a fast moving fire.
I can’t help but wonder how much different it makes that the species inhabiting that particular area have changed since the LIA and MWP.
One reason for fire suppression has been to protect logging interests. Someone with a reasonably valuable stand of timber probably gets a bit upset when it burns. This might be particularly true in cases where the local population depended on those trees for their livelihood.
From the article: “Today’s extreme droughts caused by climate change probably would not cause megafires if not for a century of livestock grazing and firefighting, which have combined to create more dense forests with accumulated logs and other fuels that now make them more vulnerable than ever to extreme droughts. One answer to today’s megafires might be changes in fire management.”
I’m having trouble getting a handle on this. It poses more questions than it answers. Extreme droughts are common throughout history. I believe they are saying that grazing and fire suppression techniques are causing the megafires, but are extreme droughts really a product of climate change or are they merely due to natural climate variability? In fact, is climate change a result of natural climate variability or largely or partially human-induced? This last, of course, is the great question in the great debate of our time.
The other question I have is this: do megafires have adverse effects beyond those of the historic limited types of fires? I’ve seen the consequence of a mega fire in the Oakland Hills in 1991 and I also saw the area, which had a lot of steep terrain, regenerate rather quickly in the decade after. That was actually a wildland fire within the city limits that destroyed three thousand houses, so it might not be relevant here.
However, I own a parcel here in north San Diego County that burned shortly after I bought it in 2000. It (the chaparral) is almost entirely regenerated now, and I am making sure that in the event of another fire, my house will not burn. The lot had not burned in 60 years, which I was told was an unnaturally long time. And yet, everything seems to be coming back fine, although with an increase in construction in the area and the seeding that the state did afterward, there are a lot of invasive and/or non-native species of plants now thriving.
Don’t forget that Native Americans also caused many fires, to clear out the undergrowth and improve hunting conditions.
The following is an interesting letter published in the Edmonton Journal yesterday relating to a big fire a year ago and a reporter’s report. (Jeff Reimer, Grande Prairie)
http://www.edmontonjournal.com/news/Warming+easy+blame/6635352/story.html
Here is the final paragraph of that letter:
“Do people cause fires? Absolutely. Will bad fires happen again? They always have and always will. Let’s not use climate change as the easy way out or use it for sensational journalism when it is a very small part of the equation.”
“The U.S. would not be experiencing massive large-canopy-killing crown fires today if human activities had not begun to suppress the low-severity surface fires that were so common more than a century ago,” said Roos, an assistant professor in the SMU Department of Anthropology.”
More than a century ago? Even 50 years ago agricultural fire suppression was blankets and urine, if you had any of either, so until recently it is doubtfull that fire suppression had much effect on anything.
“Today’s extreme droughts caused by climate change probably would not cause megafires if not for a century of livestock grazing and firefighting, which have combined to create more dense forests with accumulated logs and other fuels that now make them more vulnerable than ever to extreme droughts. One answer to today’s megafires might be changes in fire management.”
Grazing? I guess those millions of bison did not eat much grass.
“Researchers constructed and analyzed a statistical model ……..”
Aha, now it’s all much clearer to me.
Well this is something I have had personal experience in. I was a Co-pilot on DC-6/7 airtiankers from 1988-to 1997 .One of my pet peeves was the lack of a coherent policy on conducting fire
suppression and control. More than once we set out to fight a fire that was a result of a controlled burn going over the hill in conditions that were forecast to be not good.This still happens regularly.
The ignoring of Urban/wild land interface and the restrictions on your right to keep fire from your
home.Or, in some cases the ignoring the fact that you live an area that can burn.and you do not take precautions that can enhance a fire it;s path. The waste of resources and people to fight
a fire that is not going to do anything but burn scrub, trees and/or sagebrush. Time and again we
would be dispatched to a fire literally in the middle of nowhere, like say in the middle of northern Nevada, and be the only airtanker on a 15 mile flame front.Now what? Or better yet, a two hour flight from Fairbanks north to a tundra fire with no even an Inuit village threatened.
Now the pendulum has swung the other way. Fewer crews, equipment, and roads.The forests
are clogged with brush and debris. (No I am not a believer in putting all fires out all the time,
policy that got us into trouble,) We now are setting ourselves up for another “Big Burn of 1910”
and it will be blamed on “Climate Change.” instead of stupidity..
BTW there are, approx. 17 airtankers nationwide. down from 35 a few years ago.Helicopters,
and smokejumpers are also in decline. Now What?
Dr. Bill Wattenburg has been talking about this buildup of underbrush problem on his radio program for at least 10 years so it can’t be unknown to scientists in the field. Apparently latest fires burn so hot that they practically sterilize the soil and even the seeds + pinecones that need fire to begin the germination process are being damaged instead.
Texas is attempting to deal with the convulsive megafires by allowing and promoting controlled burns. A lot of ranchers are doing it. It will also help the groundwater by controlling mesquite and juniper. We have a long way to go. SMU is just echoing the conclusions already reached by most of the state, local, and college people who are looking at this. I expect that long term, Texas will come to mandate the use of controlled burns or offer landowners incentives to manage properly with the money coming from the municipal water districts, whose customers will have a more resilient watershed as a result.
This is an excellent book on the subject of fire in North America.
http://www.amazon.com/Fire-America-Cultural-Weyerhaeuser-Environmental/dp/029597592X
The following instutition has lots of info on managing our forests and in the past had some good articles about forest fires.
http://westinstenv.org/
Does anyone know how Roos and Swetnam avoided the survivor sampling bias pitfall? It might be possible to look at fire scars on 500 year old tree-ring sets, but you can do that only on trees that survived long enough to be sampled. A major crown-type fire 300 years ago would have removed those trees from the sampled population.
This article reminds me of a story about the Blackett Operations Research Group in WWII England. I wrote it up at ClimateEtc March 7, 2012 with links.
My OR Professor, Gene Woolsey, told a story at the end of the first day of class. A WWII pilot noticed that some RAF officer with a clipboard was going out to the flightline after they landed from every mission. The pilot one day ask what he was doing. The RAF officer explained that he was “studying bullet holes on the bombers and fighters to learn attack pattern and where armor might be most effective.” The pilot having just returned after a hard mission asked incredulously, “Did it ever occur to you that you only see the planes that COME BACK!?!?” My professor closed with, “Don’t let this happen to you.”
While researching this story I found a 2007 report by Jaap de Rue, that reports the story slightly differently. Patrick Maynard Stuart Blackett lead that OR group and in their report to the RAF recommended armoring the least damaged areas since only planes that came back from Germany were included in the survey, his team reasoned that the untouched areas were apparently the most vital areas.
How true is the story? There is no doubt in my mind that the OR Group did go out and study battle damage with recommendations for changes to armor. And no doubt some people initially thought the returning planes were a reliable sample of damage from attack. But I have no doubt that the leaders quickly realized that the “planes that come back” were NOT a random sample of battle inflicted, but a highly biased one. This is the whole moral of the tale.
It is not possible to inspect the planes shot down. All you have are the planes that come back. You have to work with biased data. Understand the bias. Be aware of it, not blind to it. Make your recommendations accordingly.
Just so, it is not possible to obtain the tree ring sets of 500 year old trees when they were killed by a crown-fire 200 years ago. How did the authors avoid and account for that survivor sampling bias?
I remember taking a cross-country trip with my parents in the mid-70s and hearing that from every park ranger in every park from Colorado to California and back.
Once hiking and camping in Maine we came across the most amazing clearing. Stepping out of the forest into an area free of trees about 200-300 meters across but as far as the eye could see from left to right. The space was filled with 2m tall blackberry bushes groaning under the weight of all the huge, juicy blackberries. The place of was lousy with bears, but they didn’t have time to pay any attention to some scouts. They were too busy eating.
Our guide explained that the state sold logging tracts that were very narrow, but miles long, so the logging would create fire breaks.
Reminds me of the scene from “The Gods Must Be Crazy II” when fleeing from a grass fire, the Kalahari tribesman lights a fire. He lets it burn, then they all step into the area cleared by his burn. The pursuing flames go around them because the fuel has already been consumed. Literally fighting fire with fire.
Harold Ambler says (May 18, 2012 at 4:26 am): “I was taught about fire-suppression leading to accumulating undergrowth and more damaging fires while at summer camp in the early 1970s in the Santa Cruz Mountains.”
I remember reading the same thing in the literature while a grad student in the early 70s. In the 80s, while we were visiting Yosemite, a guide told us about the controlled burns they were using to manage the park, and pointed out a small redwood that had sprouted after a burn some 12 years before. In fact a controlled burn was in progress at the time.
crosspatch says:
May 18, 2012 at 7:58 am
…..One reason for fire suppression has been to protect logging interests. Someone with a reasonably valuable stand of timber probably gets a bit upset when it burns. This might be particularly true in cases where the local population depended on those trees for their livelihood.
___________________
Sorry Crosspatch, logging interest are not that stupid. A controlled burn is used to clean up the under-story, return nutrients to the ground and to prevent the build up of material that can cause really destructive fires. I can drive along the highway near my place and point out all the controlled burn sites here in North Carolina.
It is the econuts who get laws passed to prevent controlled burning and to prevent the clearing of brush who are directly responsible. As far as I am concerned this is a Cover Your Butt study so they do not find themselves in court where the belong.
Ever since the insurance and real estate industries matured at the end of the 19th century there has been an unusual (unPREcedented, even!) amount of surpression going on. Guess what, no small burns? BIIIIIIIIG burn!
theduke says:
You’re apparently assuming that fires happened after extreme droughts. Many places used to be burned several times a decade, drought or not. Because during a dry spell, the grass or underbrush was likely to be set on fire on purpose. Often this was not done during the driest part of the year, because a slowly crawling fire was desired, to clear the underbrush or keep trails open. So there was not a twenty or fifty year accumulation of stuff to burn.
Stephen Rasey says:
May 18, 2012 at 10:56 am
Does anyone know how Roos and Swetnam avoided the survivor sampling bias pitfall? It might be possible to look at fire scars on 500 year old tree-ring sets, but you can do that only on trees that survived long enough to be sampled. A major crown-type fire 300 years ago would have removed those trees from the sampled population.
——————————————————————————-
Exactly.
We have massive and very destructive forest fires regularly in Australia. It is one of the reasons for the dominance of eucalypts in our landscape – they regenerate very quickly even after fires which leave not so much as a twig for hundreds of square miles. Forest fires happen every year, and are usually started by lightning strikes.
While it is true that low intensity burns can reduce the impact of fire, the reality is that when a forest fire and hot, dry winds get together there is no way of slowing or stopping it using human resources. You just have to wait for a wind shift, heavy rain or the fire moving into less densely forested areas where the intensity is reduced and the fire can be fought.
As in the US, the native inhabitants used fire to clear portions of the landscape before European settlement. But, the country is so large and the inhabitants were so few that massive areas were never burned off through human intervention. Just like today, every summer there were naturally caused, high intensity forest fires which destroyed everything in their path and eventually went out again for natural reasons.