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Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

 Федеральный исследовательский центр «Красноярский научный центр Сибирского отделения Российской академии наук»

Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

To burn is natural

2 August 2019 г.

Гореть естественно
Siberian taiga burns every year but it is only in this year when the officials put forward an opinion that forest fires is a part of natural processes occurring in wild nature. How correct is the opinion that intrusion into this process is useless and it will result into the loss of resources? Aren’t fires, which occur far fr om densely populated areas, dangerous? This was the topic of an interview of a reporter of N + 1 with Alexander Bryukhanov, senior research associate of the Laboratory of Forest Pyrology at the Sukachev Institute of Forest KSC SB RAS.

Are there many burning forests?

According to the official information provided by Rosleskhos, on the average the area of forest fires in Russia annually amounts to 2,5–3 million hectares. This is the so-called «area covered by fire». It does not mean that over the whole area the forests are dead: they can survive in some place, somewhere only young trees, understory and shrubs burn down but adult trees survive. However, the estimate of fire areas in the natural environment, which is obtained by scientists based on satellite data and aerial survey, can be more than two times different fr om the estimates made by Rosleskhos: about 8 million hectares annually. This significant discrepancy can be connected with the peculiarities of the information obtained by official channels. For example, the regional authorities can inform only about the burning areas where firefighting is being done and avoid mentioning about the regions, especially the low populated ones where there is no firefighting.

One can say that 2,5 or even 8 million hectares per year is not so much: it is approximately 0,31 (or 1,01) per cent of the whole forest area in Russia covering about 809 million hectares. However, fire is the main cause of forest death in Russia , about 60 per cent annually, and in Siberia it is about 80 per cent. For many years, forest fires are the main reason to declare the state of emergency in the regions of the country. Every year several tens of people die in fire and hundreds and, sometimes, thousands of buildings are damaged. For example, in this season the area of the forest destroyed by fire approaches 7 million hectares. According to the data provided by Federal State Agency "Central Base for aerial forest protection «Avialesookhrana», by the end of July fires have covered about more than 6,8 million hectares. According to the data obtained on July, 31, the biggest area subjected to fire was in Yakutia, 2,53 million hectares, and the second position is occupied by the Krasnoyarsk Region, 1,65 million hectares.

Fires from space

"The main source of data concerning fires today is satellite monitoring, there is no other way of getting information about forest conditions in many regions. To detect fires, mainly observations in the infrared region are used, the main equipment being infrared radiometers MODIS, installed on the satellites Terra and Aqua. They observe the Earth surface in the wavelength range of about 3,5 μm, the maximum radiation of forest fire, of about 1000 K, lies in this range. Radiometers allow revealing the points of fire outbreaks, the so-called «hot spots». Hot spots do not always imply fires, they can show the enterprises of metallurgical industry. However, most of the spots are due to natural fires. The analysis of satellite data allows one to approximately determine the area covered by fire, on the average, this is about 7-8 million hectares per year, in some years it can be considerably bigger, reaching 25 million hectares. The error in the satellite data for such measurements of the total area covered by fire amounts to 1-2 %. If to consider the measurement of the area of specific fires, the error can be as big as 20%. Satellite data also allow determining long-term consequences of fires, this is also done with the help of infrared cameras working in another range, of about 1,5 µm. This range includes the band of water absorption and by observing the reflected solar radiation it is possible to determine the humidity level in forests. Also, satellite measurements are used which allow determining the amount of chlorophyll in tree canopy. Using the algorithms taking into account the evolution of surface characteristics with time and seasonal changes it is possible to estimate which part of a forest is dead. For example, several weeks after a fire optical shooting of the area in the visible and infrared range is carried out and if the amount of water and chlorophyll has dramatically dropped one can make conclusions about the degree of forest damage caused by fire.

To consider a forest as dead two criteria are used: defoliation (the amount of fallen leaves and needles) and dechromation (yellowing). If these indicators exceed 80 %, the forest can be assigned the fifth category of sanitary condition, it means that the forest is completely dead. It should be mentioned that the fourth category, wh ere defoliation exceeds 60 % is included into dead forest since in most cases this forest dies in the next year. Our estimates indicate that the average annual area of dead forest in Russia is about 3 million hectares. Moreover, in different years, the portion of dead forest can amount to 30 % fr om the area covered by fire but in other years it can be as high as 70 %", says Sergei Bartalev, Doctor of Technical Sciences, professor, head of the Laboratory of Satellite monitoring of Earth ecosystems of the Institute of Space Research, RAS.

Taking into account the fact that the total area of natural fires (these are, predominantly, forest fires) in Russia can vary fr om 5 to 15 million hectares per year, the today’s situation does not look so drastic. However, the public attitude to the amount of burning forest, whether it is great or small also, varies from year to year, it does not always depend on the absolute values of the area covered by fire. For example, in 2003 in Russia fire got spread to almost 12 million hectares of forest and in 2010, the year in which the situation was considered to be drastic from the point of view of the fire intensity, the area covered by fire amounted to 3 million hectares. The matter is that even forest fires located at a great distance of hundreds or, even thousands kilometers from populated areas can influence people. For example, in 2016 strong fires occurred in tundra on the Yamal peninsula. They were far from the populated areas and Rosleskhos did not take them into account. But it was enough for the wind to change that the direction and the smoke plume covered Moscow for a couple of days.

What processes occur in forest after a fire?

Forest fires are divided into ground and crown fires: in the first case, only litter, understory and surface cover burn, in the second case fire is spread to the crowns. Crown fires look most terrible and always damage the stands considerably. However, roots are the parts of trees, which are most sensitive to thermal impact. Crowns can sometimes be untouched and stems are almost undamaged but if fire goes deep into the soil, trees, as a rule, die.
Besides, trees have different resistance to fire. Siberian larch, for example is the most resistant among coniferous species. It grows in the regions wh ere fires occur regularly and during millions of years it got adapted to fire impact. Pine is less resistant and cedar is even more sensitive. The least resistant are black spruce and especially, silver fir (Abies). They have thin bark, the roots are located on the surface, in fir forests big roots are clearly visible. They die first, even in the case of ground fires of low intensity. Besides, their crowns reach the ground and fire easily goes up to the crown. A lot depends on the location, even if to consider two trees of the same species and of the same diameter. If one of them grows surrounded by a group of young coniferous trees most likely, it will die. If the other one grows separately from other trees, shrubs and understory, it has more chances to survive.
Finally, the conditions of vegetation and the landscape influence the type and intensity of fire. If trees grow on sand or sandy soils fire will not go into the soil, and if a tree grows on soil with a deep layer of litter which is dry and can easily burn or in the case of peat, fire will go down into the soil. Mountain landscape contributes into the transformation of ground fires into the crown ones, on a steep slope fire can easily go to the crowns, etc.

What processes occur in forests after fire depends on the soils and on the species of trees which grew here earlier. For instance, the most widely spread deciduous species in Siberia are birch and aspen. Aspen is very well adapted to fires. On the place wh ere an aspen forest dies it grows again from root springs. If, before the fire there were about only 10 per cent of aspen in the stand, after the fire among the young trees there can be 50 per cent of aspen since it is better than birch adapted to vegetative spread from root sprouts. Among coniferous species, pine is better adapted to recovery after fire, especially if there is a group of living trees in the vicinity. Pine is followed by larch. Spruce and firs are the worst at recovering. This is due to their physiology; seedlings of dark coniferous species grow better under forest canopy, in the shadow, since in the first years of their life they cannot endure very bright light. However, if their area is covered by birch and aspen, young spruce and firs can grow under their canopy. So, the recovery of dark coniferous species goes through the stage of changing species.

The period of forest recovery depends on very many factors: climatic conditions, exposure of slopes, height above the sea level, soil fertility and other parameters. For example, in the north of Siberia (Yakutia, Evenkiya), as a rule, no less than 100 years are necessary for a pine or larch to become an adult tree. In the south of Siberia the plant can become adult after 60-70 years. Consequently, for the recovery of the northern taiga, which is burning intensively now, one hundred years may not be enough.

How natural is this process?

Officials often say that forest fires are natural processes, thus it is no use controlling them, wasting resources for firefighting etc. There is some truth in these words but there is also some trickery. Scientists, really, know that fire is an indispensable factor of forest biodiversity. In South America and Australia there are plant communities having very short periods between fires. There, fires occur in the same area with the periodicity of 10-20 years. One should not forget that ecosystems of tropical and northern forests greatly differ from each other. In the tropical regions there are high temperatures and humidity all the year round and all the organic material decays and transforms into soil very quickly, no big supplies of inflammable material are formed. On the contrary, in northern, boreal forests of North America and Eurasia wh ere no quick decomposition of organic material occurs, rather big supplies of inflammable materials are accumulated. Thus, fires in these areas occurred hundreds, thousands and even millions of years ago. There is an opinion that purposeful fire prevention results in drastic consequences since with the accumulation of inflammable material a fire can be absolutely disastrous. In this connection we can give an example of a big fire in the Yellowstone national park which is said to have occurred after a policy of zero tolerance to fire had been declared. However, the pre-history of this fire is slightly different. Before the end of the 1960-ties the employees of the park tried to put out any sites of ignition, then it was decided to change the rules and «allow» small fires to preserve the health of the ecosystems. Finally, in 1988 several of such «controlled» fires joined into one and a catastrophe occurred: 3,2 thousand square kilometers burned out and two people died.
From 1997 to 2000 in Canada an international experiment on the study of crown fires and their consequences was carried out, with the participation of scientists from 14 countries. Totally, 18 experimental crown fires were performed on a plot to the west from the Great Slave Lake. As a result, scientists obtained more accurate data about the behavior of fire and smoke, rate of spreading fire, time necessary for the forest recovery. Then, a decision was made to control fire more strictly. It became clear that if the situation develops without any further control it could result into big damage. This is not the only problem. Those who say that forest fires are usual often forget that earlier fires were caused only by lightning, however, today the presence of the man in the forest or in the nearest areas and his industrial activity increases the chances of a fire outbreak by many times. Earlier, the natural time interval between fires in light coniferous forests of Siberia (consisting of pine and larch) was approximately from 20 to 50 years. There were areas which burnt once per 100 or even 150 years, these are swamplands in the Western Siberia with a dense net of rivers. However, today, due to climate changes and, especially, due to human activity the interval of fires has decreased to 5-15 years. The situation is not only directly connected with people burning dry grass in spring or throwing cigarette stubs. People change the environment essentially. For example, they cut forests for timber, mining or building roads and any clear cut is a source of a great amount of organic debris, a ready inflammable material. Thus, the risk of fire outbreaks greatly increases. The volume of wood scraps can reach 1000 m3 per 1 hectare on in the areas of clear cutting in Siberia. It can result in the development of very strong ground fires, which are extremely difficult to stop.

Is it possible not to put out a fire?

In 2015 after the forest reform all forests were divided into zones in which quenching fire was mandatory and zones of monitoring wh ere local authorities make decisions concerning firefighting. In the years of the Soviet Union, especially in the 1970–80-ties fire services tried to fight any forest fire even in Siberia and in the Far East. Bulldozers are said to have been transported to taiga by helicopters in some cases and fire was extinguished even on the reindeer pastures. Since that time the financial support of the forest industry has decreased by the order of magnitude and after the fires in 2010 it became clear that there was not enough money in the budget of the country to fight natural fires. In those years Rosleskhos set a task for sectorial research institutes (academic institutes were not concerned with this problem) to divide all the forests into zones of monitoring and zones of active firefighting.

Densely populated regions in the South were included into the zone of active firefighting wh ere all the fire outbreaks must be put out. Other, less developed areas were included into the zone of monitoring. It is difficult to say which criteria were used. The matter is that not in all the cases undisturbed taiga was included into this zone. Some settlements, for example, in Evenkia, Yakutia, in the Irkutsk and Tyumen region, as well as in Kamchatka got included into this zone. In these areas there is industrial activity: timber logging and mining. However, to fight fires in these regions is not obligatory; it is the decision to be made by the local authorities, to be more exact, by the Commission on Emergency Situations. According to the law, they must begin quenching fire if it approaches a populated area closer than five kilometers. However, very often regional authorities do not have enough funds. For instance, strong fires in Evenkia occur very often. Almost the whole republic is in the zone of monitoring. In the south of Evenkia, however, there is timber industry, geological exploration and mining, as well as the oil pipeline Tayshet-Kuyumba and roads have been built for people to live and work. In the Soviet time in the south of Evenkia, in the settlements Baykit and Vanavara there were airplane departments which, in the season of fires, employed about 30 professional airborne troopers. Now, these professionals are absent there. Those who say that the zones of monitoring are very distant areas and there are no roads and no people, show a false face. Really, people get profit from these areas: from timber, oil, fur. However, neither the region nor the whole country have funds to take care of this area.

How to control fire?

The distribution into the zones of monitoring and zones of active firefighting must be reconsidered. It does not mean that only the boundaries must be moved to the north or changed. It is necessary to change the approach to forest protection and start doing what is in the West called fire management, control of fires. Now, forests are divided into two parts, and one of them is fully ignored in planning measures for protection from fire. But these parts are not divided by a wall and nobody can guarantee that the processes occurring in the zone of monitoring and control will not influence the processes in the other zone. Big fires occurred in Siberia earlier, in this century as well, but in those years the bigger part of the smoke plume disappeared in the Arctic. This year the smoke moved to the west and south-west. So, now everybody knows about the fires, breathing in this smoke, though, this is the smoke of fires located in the zone of monitoring and control.

The state must have specialized professionals – forest rangers. Though, in 2006 with the adoption of the new Forest Code the service which had been working for tens of years was eliminated and thousands of forest rangers who monitored and controlled the state of the forest, and logging, were involved into the fire prevention, were fired. Today, in Russia 18-20 thousand rangers protect forests, the same number as in Belorussia. In the USA and Canada nobody divides forests into parts for a fire to be put out in one part but not in the other. Forest rangers are present everywhere, they must put out small fire outbreaks, control the accumulation of inflammable material, organize fire breaks. They can even do controlled burning to prevent big fires or improve conditions for forest recovery. The professionals determine natural fire borders and if fire crosses these borders they begin firefighting. Catastrophic events are, naturally, possible in the US and Canada. Our officials enjoy saying: look, Americans were unable to control the situation with fires in California. One must understand, however, that in the last year there were extreme weather conditions in California: the wind Santa-Ana, blowing at a rate of 40-60 km per hour, instantly blows up any smallest fire outbreak. We have no extraordinary situation; the fires in Evenkia and Yakutia are spreading slowly, day by day. After weeks and months they spread to great areas because nobody puts them out. The biggest problem is that in Siberia and in the Far East forest management hardly gets any financial support. Measures must be taken every 10 years, according to the law. Forest managers must come to forests and observe growing and dead vegetation and estimate risks of fires. However, in Siberia and Far East forest management has been absent for 20-30 years and even more. So, the authorities have very little control over the situation and do not know what unpleasant surprises can come from the taiga.