Earth & Sky

The following person was interviewed for today’s program. Our thanks to:

Dr. Larry D. Hinzman
Water and Environmental Research Center
Institute of Northern Engineering
University of Alaska Fairbanks

Additional Resources;

Busy wildfire season predicted,Less devastation expected than in 2002 – May 31, 2003 (Edition.CNN.com)

Consequences of Global Warming (Natural Resources Defense Council)

New Mapping Initiative Provides Most Accurate Picture Yet of Threatened State of World’s Remaining Boreal Forests (GlobalForestWatch.org)

Silvics of North America (Northeastern Area State & Private Forestry, U.S. Forest Service)

Interview with Larry Hinzman:

ES: Thanks for talking with Earth and Sky today. Could you please tell me about yourself.

LH: I’m Larry Hinzman, a research professor of Water Resources at the University of Alaska in Fairbanks.

ES: Well, let’s get started by talking about the FROSTFIRE project. Could you tell me about it?

LH: The FROSTFIRE project was conceived because we had been conducting research in a watershed for many years that was in a relatively remote part of Alaska, about 30 miles north of Fairbanks, in an area where a wildfire could be experimentally conducted safely. And we have a huge amount of background data, so we’ve got a really good understanding of what the natural dynamics of the watershed are. And so by conducting this experiment in this watershed, we were able to see what the impacts would be to the hydrology and to many of the other factors, such as the ecology, the carbon dynamics, the soil-gas fluxes. What we did was look at the hydrologic processes. And we’ve run many climate stations in this watershed for many years, but in the year preceding the fire, we conducted many other background studies to quantify how much carbon there is in the above ground vegetation, how much carbon there is in the organic soils, and how much carbon there is in the deeper permafrost. And this is the first fire that was conducted in a permafrost-dominated watershed. And that’s very important, because the vegetation is very much controlled by the underlying permafrost. The permafrost is very ice-rich – it doesn’t permit water infiltration to the ground water. It holds the ground water near the surface. And so the surface soils are very wet. That has a big impact on the type of vegetation that grows there. We have a lot of black spruce and mosses and very organic rich soils, so it carries fire very well. There were many scientists involved in this project. There were approximately 50 different scientific research groups looking at everything from quantifying the flux of carbon dioxide and methane from the soils, to quantifying the amount of carbon in the canopy of the tree stands, to looking at the actual fire behavior, modeling the spread of the wildfire and looking at how it carries through the watershed. And we also had groups studying the flux of carbon into the atmosphere and transport of particulates into the atmosphere and out onto the arctic ice. There were many different research groups who were studying the natural background data of the watershed to quantify the current stream chemistry, to quantify the prefire stream chemistry, the prefire organic carbon levels in the soils, and so they were able to look at the impacts of the fire, and to see how that changed from these preburn surveys to the post-fire activity.

ES: Can you talk a little bit about the boreal forest?

LH: The boreal forest is one of the largest ecosystem types in the world. It spans across much of northern North America and across northern Eurasia. It’s a huge landscape type. It’s also quite sensitive to a changing climate. Now the fire frequency in the boreal forest has been increasing dramatically. The fire frequency is in the number of forest fires, the area burned, in North America has doubled in the last 50 years. We often see that the permafrost degrades after a wildfire. And if the permafrost degrades, and our highly organic soils become drier, them they become more prone to fire and they essentially enhance the positive feedback. So it’s very important, not only to understand what the effects of wildfire are in the current boreal forest under the current conditions, but it’s also important to project how wildfire frequency and extant and severity will change with the changing climate.

ES: Why does the fire frequency increase in the boreal forest?

LH: We know that the fire frequency is related to the climate. We know that the climate is changing, and we know that the fire frequency is increasing. I suspect that what we’re seeing – in the Alaskan regions – is a drying of the soils in response to warmer temperatures. We get warmer temperatures, we get more evaporation, we get drier soils and we get drier canopies and an increase in the flammability of the forest. In the North American boreal forest, across Canada, you’re also seeing significant warming across Canada. And we’re probably seeing greater rates of evaporation there and probably drying of the canopies and drying of the soils there – increasing the flammability of those forests too. There have also been documented increases in the fires in the Siberian boreal forest, and one of the factors may be the changing climate, but it also could be increasing population. And so there’s a higher rate of ignition sources. In Alaska, most of the ignition sources come from lightning. So the human populations are not having that big an effect compared to just the drier climate.

ES:

LH: Coniferous forests are very fire-prone when they are dry. When they are dry, coniferous trees such as spruce and pine and larch – particularly larch – those are all dominant tree species in the boreal forest. So the fire frequency in these coniferous forests can be very high, it can be between 80 and 150 years. That means the return period – we’ll get a fire from anywhere between 80 to 150 years. We also have a lot of deciduous trees mixed in with the boreal forest such as alder and birch, and their fire return period is less. They’re not as fire prone as the coniferous species. And also, we have in the boreal forest, very organic soils with thick moss layers on the surface. When these layers become dry, they become very, very prime fire ignition places. They have very high flammability.

ES:

LH: The FROSTFIRE experiment was the first wildfire experiment conducted in a watershed that was underlayed or dominated by permafrost. Permafrost is permanently frozen soil, or soil that’s frozen for more than two years continuously. Much of the boreal forest is underlying by permafrost. And the permafrost has a very, very dominant impact on the surface processes such as the ecosystem types, the permafrost will hold the water near the surface and so you can get a very different species over permafrost than you will get in areas that are permafrost free. So permafrost has an effect on the surface ecology and it also affects the surface hydrology. It holds the water near the surface, and it also has an impact on the local climatology in that the surface energy balance over permafrost areas is slightly different than in areas that are permafrost free. With a wildfire, what we will often see is, immediately after a wildfire in the boreal forest there are typically stand killing fires in the Northern boreal forest where they kill all the vegetation, and at that point the surface is very black. It absorbs more of the soil energy, and so the surface soils become warmer and wetter. Since the surface vegetation is killed, there’s less transpiration, so the soils become wetter. As the soils become warmer, the permafrost begins to warm and thaw, and consequently degrade. Now, as the permafrost degrades, it can no longer hold the moisture near the surface. And so as the permafrost degrades, the water is better able to infiltrate to the ground water, and then the surface soils become much drier. As the surface soils become much drier, then the vegetation that was there prior to the burn is no longer as conducive to growing that type of vegetation. The conditions are not prime for the hydrophilic – the water loving – vegetation. So the ecosystem can change dramatically. Now, the question is, under the current climate, as we see the permafrost degrading after a wildfire, as the vegetation recovers, will that permafrost recover? And will the ecosystem return to the prefire condition, to the prefire vegetation, or will it change to a different community types and different biome types. And that is a possibility. In many cases we do see that after a wildfire, the permafrost degrades, and in many places we see that the permafrost is not recovering. And we are seeing a change in the community types.

LH:

ES: Permafrost has caused a tremendous buildup of organic carbon in the soil. We have huge peat storage underneath the permafrost. The soils are cold and wet. And so the plant material dies, and it gets buried, and it doesn’t decompose well due to the cold, wet soil. Now, as we get a surface fire and it goes through and burns off the surface vegetation, it changes, or warms, the permafrost, warms the soils below it. And the amount of carbon that is released from wildfires is tremendous. The amount of carbon that’s released from the burning of the vegetation is huge. But it’s actually less than the amount of carbon that’s released in the years following the wildfire from the decomposition of the organic carbon in the soils. So these wildfires have a huge impact on the carbon balance.

ES:

LH: Permafrost forms in the cold, northern areas. Around the northern boreal forest we have discontinuous permafrost – that is – it’s not continuous everywhere. We find it in the valley bottoms and the north basin slopes. As we go farther north, in the Northern Hemisphere, permafrost becomes more spatially extensive, and we begin to find it continuously in the southeastern slopes and everywhere. Permafrost promotes the development of the thick peat layers, the development of the buildup of organic matter in the soils. The permafrost essentially holds the soil moisture – prevents the soils moisture, or infiltration of the groundwater. Some soils are cold and wet, and the organic matter doe not decompose rapidly, so the organic matter continues to build up, and we get thick peat layers developing. Now, as we get wildfires, those wildfires can warm the surface and cause that permafrost to degrade somewhat. As the permafrost warms and degrades, we see the improved infiltration, improved drainage in the soils, and so the soils become drier. When we have warmer, drier soils, now we can get improved decomposition of the organic matter in the soils. With the increased decomposition of the organic matter we get a greater flux of carbon dioxide and methane from the soils leading to a positive feedback from the fire. So we’re getting a warming and drying of the soils, which can cause an increased fire frequency. With the increased fire frequency we can also get more carbon released from those carbon storehouses, those peat storehouses, in the soils.

ES: It almost seems like a viscous cycle.

LH: I don’t know if it’s viscous. This is a positive feedback loop. We are seeing increased fire frequency. As we get increased fire frequency we getting degradation of the permafrost. As you get degradation of the permafrost, we’ll get drier soils and increased decomposition of the organic matter and more carbon going into the atmosphere which should cause greater warming.

ES:

LH: A goal for the FROSTFIRE project was – we had many goals – we wanted to develop a better a better understanding between the relationship between climate and wildfire. We also wanted to improve the fire behavior model, we wanted to develop better fire behavior models in the permafrost regions. Many of the models were developed in northern Canada, in the non-permafrost areas, and we wanted to test that fire behavior – fire spread models in this watershed. So we were able to develop the pre-burn data that was necessary to parameterize these fire models before the fire, and then we were able to test that – to monitor the fire behavior and watch the fire spread, watch how it related to the < a href=“http://forestry.about.com/library/weekly/aa102499.htm”>fire weather, that is, the weather immediately during the burn to see the fire behavior. We conducted preburn investigations for about one year, and the fire was actually ignited in July of 1999. This was a very large project, which was a collaborative effort between the Bureau of Land Management, Alaska Fire Service, the U.S. Forest Service Pacific Northwest Research Station, and the University of Alaska. But there were many other scientists from across the nation, from Japan, Brazil, Russia, and Canada who also participated in this effort. The fire was ignited in July of 1999. It burned for three days, and on the fourth day we began to get decreased relative humidity and some precipitation which extinguished the fire. The Alaska Fire Service invested over 6000 hours prior to the burn in cutting a perimeter around this 1000 hectare, or about 4 square mile, watershed. The perimeter was about 30 meters wide and it was blackened, it was burned, so there was no vegetation in that perimeter all the way around the watershed. The Fire Service strategically placed water tanks all around the watershed and actually plumbed the entire perimeter of the watershed with 2-inch fire hose so they were able to fight the fire if necessary. There were over 100 fire fighters on the ground during the burn. There were several spotter planes that were circling and looking for wildfire escape, or spotfire escape. And there were also two aerial tankers that were on the ground in Fairbanks, two aerial tankers filled with fire retardant, on the ground in Fairbanks, should they be needed.

ES: Were you at ground zero, or rather where were you during the fire?

LH: I was viewing the fire from a safe distance. There was one ridge that was across the outside of the perimeter of the fire that we were able to sit upon. On this ridge, it was at the Poker Flats Rocket Range, we had an excellent view of the watershed and there were numerous cameras set up there, so we were able to record the fire spread and there were also numerous cameras in the helicopters and in the spotter planes, so they were able to record the fire behavior there.

ES:

LH: There was a subdivision that was about three miles away from the perimeter of the fire line. This was separated from the fire by wetlands and by some deciduous trees which don’t carry fire very well. But the residents of this subdivision were justifiably concerned about holding a fire, essentially in their backyard.

ES: Why did the scientists choose that particular area?

LH: This watershed was developed as a study area in 1967. In Fairbanks we had a big flood in 1967. At that point, many of the state agencies got together and decided that Alaska really didn’t know enough about the local hydrology. At that point they decided that we needed to develop a research watershed where we could study the local hydrology to develop a better understanding of how hydrologic processes can impact society. At that point, that group set aside this large research watershed, the Caribou-Poker Creeks Research Watershed, for hydrologic and climatology studies. And disturbance studies were identified as a component as one of the areas that this watershed should be utilized for.

ES: What do you mean by disturbance studies?

LH: Disturbance studies means that this wildfire was actually the first disturbance, but a wildfire definitely is a disturbance. Essentially we have 30 years of background data now. And so we have a really good understanding of what this watershed is like and what the natural conditions are in this watershed. And this is a relatively low-populated area. It is relatively accessible, it’s just off a highway about 30 miles out of Fairbanks, so it’s an area that we were able to get a large group of scientists into and an area that we were able to get the firefighters into easily everyday to build the fire lines and essentially prepare the watershed for the wildfire.

ES: What were some of the obstacles you encountered on this project?

~~~LH: Well, there were many obstacles to actually conducting this fire. The biggest obstacle was actually the weather. We had a very tight prescription window that we could actually conduct this fire in. It could not be too dry or too windy that the fire could not be safely contained But it needed to be dry enough, and the conditions had to be correct so that we could ignite the fire, and that the force would be dry enough to actually carry the fire. And it’s surprising that those conditions do not actually exist very often. If you pick an area, and you try to get a fire to burn in that area, it’s not that easy to actually conduct that, to get that to happen. ~~~ After analyzing the fire weather data for a particular area for a long time, I think we were actually very lucky to be able to conduct this fire during the three year period of our research grant from NSF. We also had other obstacles.

There are other issues that we had to consider in that prescribed burns are not a common practice in Alaska. So we had to go to a great effort to educate the public about what prescribed burns were and how they could be conducted safely. And we had to develop a well-developed burn plan where we could be confident that we could actually conduct this wildfire safely and contain it, so that there would be no escape.

ES: Why would you chose to study a prescribed burn rather than a naturally occurring wildfire?

LH: Unfortunately, there are many, many wildfires that occur in Alaska and across the North American boreal forest. But it’s very difficult to bring together a very large team of multi-disciplinary scientist where we can all work together in one area. So we can study the changes in the carbon dynamics, we can study the changes in the stream chemistry, we can share our data and study the effects on the vegetation recovery and document how the vegetation recovery may change with changing burn severity. But it’s almost impossible to bring that large of a group of scientist together, unless you can prepare many years in advance. Unless you can say when a fire is going to occur and where it’s going to occur, and allow the scientist to collect their pre-burn data and allow the scientist to work together to share their data. And it’s not possible to do something like that under the normal wildfire conditions. There’s no way that you can bring a large group together to get the background data they need before a wildfire occurs. There are chances in a wildfire where small groups of scientists, one or two people could fly in and front of the fire and collect some measurements or study the wildfire behavior. But it’s not possible to document changes in stream chemistry unless you’ve got a good idea of what the stream chemistry is before the fire.

ES:

~~~ LH: Well, this has been a hugely important project, and there have been many good publications that have come out of it. I think one of the most important aspects that have come out of this is the role of fire in a changing ecosystem. As far as, we see the climate warming, and we expect that we see a change in the ecosystem, but we think that the ecosystem is just going to respond to a change in climate – warmer temperatures, greater precipitation. But actually what we’re seeing is that fire has a role in changing those landscapes. In that we see the climate warm some mud. We see the vegetation becoming drier and it becomes more prone to fire. And as the fire comes through, it causes a rapid threshold change, or a step change in the ecosystem type, in that we may see a degradation of the permafrost. And from that we may see a shift in the vegetation trajectory. Instead of the successional pathways going from back into a coniferous species that were there prior, we may see a change to a deciduous species. Or we may see a change to grassland. And so one of the big surprises has been how wildfire affects the permafrost, and how that carries on to affecting the ecosystem types.

ES: How are wildfires in the permafrost region different than wildfires in more temperate regions?

LH: Well in the permafrost regions we have thick, organic soils. So we don’t just see a wildfire that goes though and burns off the small needles and continues on to leave the ground essentially intact, as you may see in the forests of California. We see a fire that does go through the canopy of the trees. But then we also see the fire burns the organic soils themselves. And we see a long smoldering. The organic soils, the peats become ignited, and they may burn for days, weeks, or months. So there is a substantially different ecosystem type. So we see substantially different response to the fire. And I talk about burn severity – burn severity is very important in the boreal forest. Burn severity is not actually caused by the temperature of the fire during the burn. Burn severity is actually caused by how long the fire will smolder after it goes through. And so if we have very dry conditions, and it burns very hot, we ignite the organic soils. And if we don’t get precipitation within a few days after a fire, it can burn for a very long period and completely combust all of the organics in the soil. If we burn off all the organics in the soil, that removes completely the insulation, that surface organic layer is the insulation for the permafrost. So if we burn off all of those surface organics, that removes that layer of insulation from the permafrost. And that causes more rapid and more drastic degradation of the underlying permafrost.

ES:

LH: We do control degradation of permafrost around structures, around buildings, around bridges or pipelines. We can do that, we can put in active refrigeration. But there’s no scale that can control degradation of permafrost on the scale of the boreal forest or even on watershed scales. Now there’s nothing we can do to prevent that degradation of permafrost on the watershed scale.

ES: Did this prescribed fire behave very much like a natural wildfire?

~~~ LH: Wildfire are very much dependent on the weather at that particular minute in that it was ignited artificially, but then it took off like a wildfire, And it was ignited on the first day, and then for the next days it burned like a wildfire. And so the fire increase dramatically, as the temperatures increased and the relative humidity dropped, and it rose into a crown fire and it took off up into the watershed. And then as the temperatures cooled, and the relative humidity increased, then the fire calmed down somewhat. And then when it began to rain on the third day, the fire essentially extinguished itself. So it was very much like a wildfire. ~~~

ES:

LH: I guess I’d like to say, there are still several questions that remain from this study, and things that we need to continue to investigate. We need to understand if the degradation of the permafrost is going to initiate a cascade of impacts, such as soil drying and vegetation change. Are these going to result in other unforeseen climactic feedback? We need to know if the permafrost will recover from these severe fires in this subarctic climate, or will they continue to degrade indefinitely? Is this going to be a response to the climate, or is it going to recover? Is it going to be a dramatic threshold change, or will we return to the pre-burn conditions?

ES:

LH: These forests have a tremendous value to the timber industry, and they are also a huge storehouse for carbon, as far as in the global carbon credits, they are also important in that respect. But they also serve as a very valuable ecosystem in their own right. So yes, the value goes from the economic to the sublime.

ES:

LH: It is very difficult to project how the boreal forest is going to change. There are many investigators that are studying climate change, and what the impacts will be using dynamic vegetation models. And they have documented that the boreal forest is a very sensitive ecosystem. They projected that up to 40% of the boreal forest could change to a completely different biome – that is parts of the boreal forest could change to more of a grassland type. Parts of the boreal forest could change from being dominated by coniferous trees to being dominated by deciduous trees. So the potential impacts are difficult to assess. It depends on what the climate does.