Дата публикации: 17 сентября 2021
Автор(ы): Andrei SIRIN, Tatyana MINAYEVA, Anna VOZBRANNAYA, Sergei BARTALEV →
Публикатор: Научная библиотека Порталус
Рубрика: ЭКОЛОГИЯ →
Источник: (c) Science in Russia, №2, 2011, C.13-21 →
Номер публикации: №1631881599
Andrei SIRIN, Tatyana MINAYEVA, Anna VOZBRANNAYA, Sergei BARTALEV, (c)
by Andrei SIRIN, Dr. Sc. (Biol.), RAS Institute of Forest Science, director; Tatyana MINAYEVA, Peatlands Projects Coordinator, Wetlands International; Anna VOZBRANNAYA, Senior Researcher of the Science and Ecological Education, "Meshchera" National Park; Sergei BARTALEV, Dr. Sc. (Technol.), department head, RAS Institute of Space Research
Peatlands and paludified land with shallow peat cover more than one-fifth of Russia's territory. Such land cannot be utilized without drainage. As abandoned drained peatlands turn into time bombs on account of their high vulnerability to fire, responsibility for their future falls to Man. How can we avert this danger?
Numerous peat fires burst out in European Russia during the summer of 2010. The products of incomplete combustion of peat combined to form an acrid smog, and the problem was compounded by a lingering heatwave. It looked like a real natural calamity. We have lived through phenomena like this before--say in 1972 and in 2002. But these were only the worst cases. Our country's vast expanses and varied climatic conditions mean that, in fact, such episodes occur every year, although usually at smaller scale. They
also took place in the 19th and earlier centuries. Generally, fire-fighting measures have been intensified only when the pungent smoke of burning forests and peatlands have covered St. Petersburg, which was the capital city in the 18th, 19th and early 20th centuries. Then came the fires of the hot summer of 2010. Inadequate fire prevention and fire-fighting activities were partly to blame for their impact. We simply did not respond fast enough. Measures to get on top of the problem once and for all, for instance by re-wetting potential flashpoints, were proposed. Why not? But how realistic is this approach in practical terms? Is it practicable at all?
Peat bogs (living peatlands) are natural ecosystems with three essential characteristics, namely: water surplus, specific vegetation types, and deposits of peat. The high moisture level supports helophytes (mire plants) and slows down the decomposition of their dead remains, which thus accumulate as peat deposits and become the soil. Owing to its unique physical properties, peat absorbs and retains 10-30 times its own dry mass of water. It retains moisture even during droughts. A change of hydrological conditions resulting from drainage has harmful after-effects; it alters the organic matter balance, intensifies decomposition, and promotes wind and water erosion. Climatic and other causes can give rise to similar effects.
The natural conditions in many regions of Russia are conducive to paludification and peat bog formation. However, because we still have no unified cadaster system, peatlands are allocated to different land categories (Forest Fund, agricultural lands, Water Fund and so on). As shown by the "Peatlands of Russia" geoinfor-mation system launched in the 1990s at the RAS Institute of Forest Science (project leader Acad. Sta-nislav Vomperskiy), peatlands cover at least 8.1 percent of the country's territory, and as much as 21.6 percent if paludified land with peat less than 30 cm thick is included. The Institute of Forest Science has been closely involved with peatlands and their ecosystems throughout its long history--having been founded back in 1944 on the initiative of Acad. Vladimir Sukachev, whose works published even before 1917 laid the groundwork for mire science in this country.
Peatlands are a source of many essential natural products, and so cannot be divorced from commercial interests; for instance, peat is indispensable to hothouse plant-growing. Moreover, the avoidance of such large
tracts of land would place impossible constraints on the further development of agriculture, transportation and other activities associated with land use. Thus, our interest in peatland "improvement" has been gaining momentum since the end of the 19th century. As much as 5 million hectares of peatland and paludified land have been taken in for agriculture, 4 million hectares for forestry and nearly 1.5 million hectares for peat extraction. These projects have involved a number of districts in European Russia's heartland, mostly in the northwest and along the Volga. But due to errors in project design and subsequent mismanagement, a considerable part of the drained acreage is now in unsatisfactory condition and generating ecological problems and fire hazards.
Peat fires occur naturally in many Russian peatlands and paludified lands, from the tundra of the Far North, through the taiga forests to the forested steppe lands down south. Peatlands up in the mountains are not spared either. Even raised bogs catch fire during severe droughts. Raised bogs are peatlands that are fed only by atmospheric precipitation, in which drying-up of the layers of dead moss (top spit) and loose peat just below the surfaces of their characteristic moss cushions (hummocks) serves as a self-defense mechanism to protect the rest of the peat deposit from drying. This mechanism cuts the pathway for capillary upflow of water and thus slows down evaporation. Simultaneously, however, the fire risk increases, and only small pools and other depressions (hollows) that remain wet can prevent the fire from spreading.
In 1997, Andrey Sirin (one of the authors of the present article) and Dr. Vladimir Klimanov of the RAS
Institute of Geography published an analysis of available data on peatland growth rates in northern Eurasia over the last three thousand years. This showed a slow-ing-up of growth during warm paleoclimatic periods. The associated changes in water regime also increased the probability of peat fires, which leave their own evidence in the form of charcoal and ash layers within the peat. Most of the peatlands in Central European Russia are at least ten thousand years old, and whilst some of them have been on fire only once or a few times since the last Ice Age, others have flared up much more frequently.
Special field studies which began in 1999 at the West Dvina Peatland Forestry Experimental Station of the RAS Institute of Forest Science (Tver Region) have shown that peat fires wipe out most of the standing crop of trees. Burning of the dwarf-shrub vegetation layer increases the temperature and intensity of the ground fire, promoting damage to the cambium of tree stems and to roots at the tree base; and pushing the fire deeper so that it consumes the fine roots that are most important for absorbing water and nutrients. On the other hand, fires improve the fertility of peat soil by changing its structure and raising its ash content so that roots can use it more effectively.
The composition and distribution of organic remains within peat deposits shows that fire does not generally have a lasting and irreversible effect on peatland ecosystems. Rather, the peatland returns to its previous evolutionary pathway within a century or two, although the re-establishment of forest stages may take longer. On the other hand, small (dozens rather than hundreds of acres) and shallow (0.5 m thick) peat blankets can burn
out completely, with only their vegetation eventually recovering. Joint studies carried out by Russian, Belorussian and German peatland scientists on sites in Tver Region and published in 2008 indicate that areas with shallow peat layers exhibit the highest carbon accumulation rates, far exceeding those of both mineral soils and deep peat bogs. The cycle of peat formation and burning-out may have occurred time and time again at such sites; who knows? Unfortunately, the fires have completely destroyed any "archival" evidence in the peat deposits. Where peat has survived, it is an important source of information about the climates of ages past. The plants remains, their isotope composition, and the spores and pollen deposited in the peat can all be used to help reconstruct the historical pattern of vegetation and ecological regime change, both on the peatland itself and in its surroundings.
Fire may eat deep into peat with water content as high as 200 percent or more by weight. The heat released dissipates only poorly and so warms up adjacent parts of the deposit. Once charred, the next section of peat catches fire and burns on even if it is moist. Therefore, peat fires are difficult to extinguish, and can smolder on through autumn rains and beneath snow cover all through the winter. They may continue for years; examples have been documented from Spain, South Africa, Indonesia, Malaysia and elsewhere.
Peat fires can be started by sparks and flames from forest fires nearby, and lightning is an occasional cause. Drained peat bogs may also catch fire because of the notorious human factor-bonfires, carelessly discarded cigarette butts and the like. Furthermore, there are cases of possible self-ignition, particularly in stockpiles of milled peat made during peat extraction operations, where even an ounce of care and prevention measures is worth its weight in gold.
Land improvement projects should provide for the protection of peatlands against fire. Suitable measures may cost as much as 15 percent of the total estimated cost of the project. They may involve the construction of a system of ponds, water conduits, diversion canals, pump-houses etc., similar to those already recognized as essential parts of drainage projects for agriculture and, especially, forestry. The principle is to create a ring of protective canals and ponds with emergency escape passages, both to prevent the fire from spreading and to enable access by people and fire-fighting machinery to places of combustion. Precautions like these mean that there are relatively fewer cases of uncontrolled peat fires on peatland that has been drained for forestry than on peatland in general.
In fact, fires on drained and used peatland pose a lesser threat than on natural peat bogs, thanks to the potential for their prevention and extinction in the earliest stages. However, the situation changes drastically for the worse when drained peatlands are abandoned. Nowadays, more than one-third of the acreage that has been drained for agriculture is not used, and much of it is in poor condition. Forest drainage systems are, similarly, no longer overhauled, and in some places the provisions for fire protection have consequently gone out of commission.
Abandoned peat-milling areas that have not been reclaimed are the worst culprits. Since the late 1940s, this technology has accounted for as much as 90 percent of the output of commercially extracted peat nationwide. Peatlands destined for milling are first divided by ditches into technological plots (production fields), each 20 to 40 meters wide and 500 to 1,000 meters long. This reduces the pore water content of the peat to a level suitable for layer-by-layer cutting. Weather permitting, as many as twenty layers may be milled off the surface and collected in a season. A production field
may be used continuously for 15 or more years, depending on the depth and other characteristics of the peat deposit. Formerly, in Soviet times, it was required that cutaway peat deposits were re-cultivated and returned to their previous status within the Land Reserve. A basal peat layer had to be left intact, and its thickness was specified according to whether the subsequent land use would be farming, forestry, fish breeding etc. Cutaway peatlands were seldom re-wetted because the policy impetus was to expand cultivation, and even areas converted into domestic gardens were deemed to have been returned to agricultural status.
The area of non-recultivated cutover peatlands continued to rise with the output of peat, reaching a peak in the 1970s and 1980s. The situation took a turn for the worse with the collapse of the peat production industry during the 1990s. Overall, Russia now has as much as one million acres of abandoned peat fields, mostly in the Vladimir, Nizhni Novgorod, Leningrad and Tver regions, with Moscow region in the lead. Although they are a legacy of the general activity of the whole country, these peat fields have become a big headache primarily for the local authorities that host them. To add insult to injury, they are located in densely populated districts where the
Science in Russia, No.2, 2011
socioeconomic situation is not at its best. On the other hand, intact peat bogs are becoming fewer and fewer in the heartland of European Russia, both along the Volga and in other regions, according to the "Peatlands of Russia" GIS that has been mentioned already.
How might we cope with this situation? The growing instability of climate means that droughts will occur ever more frequently. Because peat bogs are vulnerable to fire mostly from the outside, fire prevention should be focused on the neighboring forests and agricultural lands. That is the key step in warding off the fire hazard. We should also be very careful not to play with fire within peatlands. Abandoned peat production fields, which catch fire time and time again, are the number one problem; for ecological as well as other reasons. One important consideration is that, because they are subject to wind erosion and intensive destruction and decomposition of peat, they release carbon dioxide into the atmosphere.
Unfortunately there is little or no prospect that abandoned peat production fields will self-regenerate because their drainage systems are still at work, drying up the peat and turf so they can offer only inhospitable habitats for peatland plants. The older "wet" techniques of peat extraction (hydraulic and excavated), which were practised widely during the first half of the 20th century, happened to be more ecofriendly, and bog vegetation recovered quickly afterwards. The prospect of resuming these ecologically safer methods of peat extraction is being discussed in many countries, but high energy costs emerge as a limiting factor.
Thanks to the concerted efforts of ecologists, researchers of the Russian Academy of Sciences and the peat extraction industry, the Water Code of the Russian
Since 2003, as much as 2,000 of the 7,500 hectares of abandoned dry milled peatland in the "Meshchera" National Park have been re-wetted, and the fire hazard thus reversed.
Federation (2006) defines re-wetting as a priority method for the after-use of depleted peat deposits. Re-wetting requires that the water table should be raised considerably relative to the surface of the peatland, and the probability of success is highest in depleted peat deposits. Hence, it is desirable to resume working on abandoned areas where peat deposits are still present. Among other considerations, this would cater for needs in many branches of the national economy.
Strategies for re-wetting extracted peat fields can be optimised. The RAS Institutes of Forest Science and Space Research have set up a system of satellite monitoring for abandoned peat fields which is designed to spot the locations where fire risk is highest. The system has been tested for the peatlands of "Meshchera" National Park in Vladimir region. It has been shown that only specific sites, rather than all of the production fields, need be re-wetted. In some cases, active intervention on only 10 percent of the acreage will be sufficient to enable spontaneous choking and overgrowing of drainage ditches, coupled with natural paludification, to take care of the rest; but in other cases as much as two-thirds of the territory would need management.
How can we translate all of this into appropriate action? We should begin with the retention of meltwater and rainfall, which will be sufficient to restore the water table to its natural maximum level during periods when precipitation exceeds evaporation. No additional inputs of water from surface or subsurface sources will then be needed (except, perhaps, in the eventuality of fire), and a good deal of red tape can be avoided.
We then need a selective and targeted approach to re-wetting, aiming to achieve optimal improvements intarget areas whilst minimizing negative consequences for adjacent land. We should take great care with this because many patches of ground are overgrown with trees and bushes which may die if the water table is raised, creating deadwood that will heighten the fire danger. The ideal method for blocking drainage ditches is to fill them up, but this is a laborious and costly job. Therefore, diversion and escape channels are simply obstructed by installing coffer-dams and dikes made from peat, timber and other locally available and ecologically acceptable materials. In a catchment area of several hectares, such impoundments perform well even during spring floods. Taller dams would be needed to span the large production fields themselves, but this technique can seldom be justified on either ecological or economic grounds.
Blocking of drainage ditches on the extracted peat fields encourages them to grow over, reduces water erosion rates, and promotes consolidation of the large dikes and dams. It also helps re-establish the natural retention of water by moss and peat. The end result is that fire is prevented.
Re-wetting of abandoned drained peatlands is practised widely in other countries; for example in Belarus, where as much as 30,000 hectares of such land has been rehabilitated in the last few years. The techniques have also been tested in Russia. More than 2,000 of about 7,500 hectares of abandoned cutaway peatland in the "Meshchera" National Park have been re-wetted since 2002 with the active involvement of volunteers and support from the RF Ministry of Natural Resources, Non-Governmental Organizations, and regional as well as local governments. Set up in 1992, the "Meshchera"
park took charge of land released by several peat production enterprises. The Russian Academy of Sciences, the "Giprotorf" Institute and Tver Technical University provided scientific support. Monitoring of vegetation and environmental variables in re-wetted areas by the RAS Karelian Research Center Institute of Biology and the RAS Institute of Forest Science has shown that efficiency varied from site to site but, overall, the peat fire risk was reduced and helpful experience gained.
Other countries, particularly in Western Europe and North America, have accumulated thirty years' experience in bog rehabilitation. But the motives were different. In some cases the aim was to restore damaged ecosystems and habitats of animals and plants. Another objective was to rehabilitate the hydrological and other environmental functions of these natural systems. Yet another incentive was to boost the recreational appeal of such territories.
Lately, this work has been attaining ever greater significance in the context of controlling the greenhouse effect. Growing (i.e. wet) peat bogs are the most efficient of all terrestrial ecosystems at removing carbon dioxide (CO2) from the atmosphere on a long-term basis. Although the emissions of methane--a gas with stronger radiative forcing effect than CO2-may be enhanced temporarily after re-wetting, the overall effect is positive, especially beyond the short term. Essentially, the greenhouse effect of the methane emissions associated with re-wetting is small compared with that of the CO2 emissions emanating from abandoned drained peatland, even without taking into account the effects of peat fires.
Here in Russia, the number one incentive for peat bog rehabilitation is to prevent fires. But there are certain collateral benefits so long as this work is conducted in a progressive and scientifically robust fashion.
Опубликовано на Порталусе 17 сентября 2021 года
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