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АРИДНЫЕ ЭКОСИСТЕМЫ, 2005, том 11, №26-27
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ОСНОВНЫЕ ФАКТОРЫ ИЗМЕНЕНИЯ КЛИМАТА И ОКРУЖАЮЩЕЙ СРЕДЫ В СРЕДНЕЙ АЗИИ
© 2005 г. М.Г. Насыров
Кафедра физиологии растений и микробиологии, Самаркандский государственный университет, 703008 Самарканд, ул. Катта-Курганская 1, Узбекистан
Возрастание численности населения, опережающий рост его потребностей, неуклонное расширение использования ресурсов региона, внедрение новых технологий и возрастание производства в энергетике, промышленности, сельском хозяйстве, транспорте, антропогенное преобразование ландшафтов, усложнение и расширение межгосударственных связей, - все эти и многие другие факторы привели к возрастающей антропогенной нагрузке на окружающую среду, с усилением взаимодействия между средой и обществом.
Заключения группы экспертов 1РСС(Межправительственная комиссия по изменению климата) показывают, что эти изменения нельзя объяснять только естественными явлениями и что имеется ясное свидетельство интенсивного человеческого влияния на ход природных процессов.
Вопрос не в том, действительно ли климат изменяется, а в том, на, сколько будет он изменяться, и как скоро и где будут изменения самыми большими. В этом вопросе есть и противоречивые суждения.
Подсчитано, что приблизительно 50-100 тысяч миллионов тонн углерода атмосферы может быть поглощено за счет превращения их в органическое вещество почв и 100150 тысяч миллиона тонн от фотосинтетической деятельности растений. Однако, объективный характер и природа этих процессов еще не ясен, и во всей вероятности, это не будет одинаковым в различных экосистемах.
В связи с этим, необходимо провести инвентаризацию выброса парниковых газов в основных сферах деятельности человека. Инвентаризация должна проводится с использованием новых инструментальных методов, позволяющих получить истинную картину происходящего в сравнительно короткое время и на достаточно больших площадях.
Анализ многолетних результатов инструментальных измерений динамики продукционного процесса показал что полынно-эфемеровые пастбища Средней Азии имеют потенциал извлекать из атмосферы и переводить в биомассу около 690 г СО2 на квадратный метр в год. На основе многолетних исследований так же удалось выявить буферную роль этих пастбищ как основного поглотителя избыточной концентрации СО2 в атмосфере.
Инструментальные исследования продуктивности доминантной растительности пастбищ Средней Азии имеют большое научное и практическое значение и могут быть успешно применены для качественной и мобильной оценки их экологического состояния в условиях изменяющегося климата.
THE MAIN DRIVERS OF CLIMATE AND ENVIRONMENTAL CHANGE IN CENTRAL ASIA
© 2005. M. G. Nasyrov
Plant physiology and microbiology Samarkand State University, 703008 Samarkand, Katta-Kurganskaya 1, Uzbekistan
INTRODUCTION
The continuous increase of desertification and degradation in semi-arid lands in Central Asia is the results of rapid population growth, the availability of modern techniques and technologies for land cultivation, as well as the loss of traditional habits and changes in traditional land use.
These major factors are additionally influenced by recent political and economic changes and collapse of the former USSR, lack of awareness among concerned parties, and the non-availability of information about current situation in the affected areas.
Although recent concern for the global environment has tended to highlight threats posed by global warming and climate change, soil erosion and associated land degradation undoubtedly remain serious problems in Central Asia.
Population growth and associated expansion and intensification of agricultural activity in many areas of the Central Asia have caused increased rates of land degradation. The region faces a serious challenge to its natural resource base. Croplands, rangelands and mountains are getting degraded. The reduced availability of agricultural inputs, and feed and fodder is resulting in a decline in livestock numbers. Water scarcity and misuse is compounding the threat to food security, human health, and ecosystems.
In order to solve these problems an integrated approach is required to identify and implement new environmentally friendly and economically sustainable agrotechnologies that deals with all the above mentioned issues.
THE PHYSICO-GEOGRAPHICAL AND ECOLOGICAL DESCRIPTION OF THE REGION
Central Asia occupies a unique place on the geographical map of the world. Being located in the center of the Eurasian continent, it is, literally and figuratively, located on the crossing of axis "North-South" and "West-East". This peculiarity of geographical location has a large influence on the cultural, political, economic, social, and ecological life of the region.
From the earliest times, the Great Silk Road, connecting the countries of East with European countries, has played the role of cultural, trade-economic transcontinental link. Ancient culture, woven of traditions and customs of many peoples, formed colorful modern face of Central Asia.
The basis of life here has always been land cultivation and cattle breeding, and water has been the main constraining factor. The beginning of active irrigated land cultivation in the region dates back to 6th-7th centuries B.C. and coincided with the highest prosperity of ancient civilization, where irrigation had always been the main decisive factor of historical and social development
The regional ecosystems are very sensitive to anthropogenic influence in connection with arid conditions. An extensive method of household operation in previous years has contributed to appearance of numerous regional ecological problems, to include one of the biggest ecological disasters on Earth, namely the Aral Sea tragedy. This region covers an enormous area of 418 million ha, of which about 275 million ha are classified as rangelands (Beniwal et al., 2000).
The most common ways of rangeland utilization are grazing, firewood and medicinal plant collection, and converting them into croplands (e.g., barley, spring wheat, and vegetables).
MAIN DRIVERS OF CLIMATE AND ENVIRONMENTAL CHANGE
The world as well as Central Asia is changing rapidly. There are several basic drivers of climate and environmental change such as population and economic growth, urbanization, human investment patterns, family structure and education, social stability, land use/land cover change, etc.
Population growth is the main problem of environmental change. By the end of 19TH century, there were some 7-8 million people in the region. Irrigated land amounted to about 3.4 million hectares and was equipped by an irrigated network. By 2000, the regional population had increased by 7 times, and irrigated areas have increased two-fold up to 7.5-7.7 million hectares.
Population growth is also one of the main reasons of natural resource decline in the region. Annual population growth in Kyrgyzstan is 1.5%, in Tajikistan, 2.5%, in Turkmenistan, 2.4%, and in Uzbekistan, 2.3%.
Although slowing, population growth is still rising and the highest rates are in those countries, which are least able to sustain them.
CURRENT SITUATION NEAR ARAL SEA
The Aral Sea, once the world's fourth biggest inland sea, has declined from a volume of about 1,000 km3 40 years ago to 110 km3 today. The water level fell within that time from 53m to 28 meters. The annual inflow in 1960 was 63-65 km3, but now it is a mere 1.5 km3. Yet 10 km3 of inflow are needed just to keep the sea as it was, let alone to reverse its plight. The mineral content of the water is now up to seven times higher than 40 years ago, with pesticides and fertilisers combining with salt to produce "a sort of salty paste". The shoreline receded by up to 250 km, leaving toxic dry deposits. Dust blown away by the wind cause serious threats to human health. Anemia, cancer, liver and kidney diseases and children's illnesses are all increasing.
The devastation of Aral Sea dates from the Soviet era, when huge tracts of Central Asia were turned into chemically intensive cotton farming. Poorly efficient irrigation systems still consume huge amounts of water that would once have reached the sea. The Syrdarya, which flows into Northern section through Kazakhstan, provides almost all the inflow to the entire Aral. The more Southern Amudarya contributes little more than a trickle.
All Central Asian countries share Aral waters and have formed the International Fund for Saving the Aral Sea (IFAS). Afghanistan has proposed to join IFAS, since 10% of the Amudarya's flow comes from that country.
Overgrazing of the rangelands by livestock is believed to be the most widespread cause of degradation in the region. Overgrazing around settlements is often related to the sedentarization of nomadic herders. The settlement of the former nomads means that their herders would be concentrated onto grazing around their homes.
Under drought conditions, these herders are forced to concentrate their animals in areas where drinking water is available, causing the complete disappearance of the most palatable herbaceous cover in many places, particularly around boreholes that provide drinking water for humans and their animals all year round.
The recent privatization processes in the agricultural sector led to changes in land use, crop yield and livestock numbers. During the Soviet era, the Central Asian republics were provided with wheat from Russia, the Ukraine and Kazakhstan to augment what they were producing locally. Each country had to plant a specialized mandated crop.
In Uzbekistan, cotton, was the major crop and was exchanged for staple foods. After the collapse of the Soviet system, the new republics had to produce their own food, mainly under rainfed conditions. Increasing wheat production had to be achieved by increasing yields and acreage given over to wheat production, both on irrigated and rainfed land. Some of the cotton-irrigated area also was re-assigned to wheat grain production.
Barley cropping on rainfed areas changed gradually. The barley overall yield decreased slowly over the years by approximately 60 kg/ha/year. This may indicate that not only were the rainfall season poor at the end of the 1990s, but also that barley cropping was relegated to the lower rainfall zones and on to the poorest soils, hence the slow observed decrease in production. It is also quite probable that some of barley production areas and also new rainfed cropping areas brought into cultivation through range clearing were assigned to wheat production. This was at the expense of the best rangelands in the
best rainfall zones on the adyr (Uzbek native word?) and also in the pre-desert areas where extra run-off could be secured (Gintzburger et al.,2003)
THE POTENTIAL OF VARIOUS ECOSYSTEMS FOR SEQUESTERING CARBON
Degradation of rangelands reduces their capacity to assimilate carbon dioxide (CO2) from the atmosphere by their vegetation for photosynthesis, and thus contributes to global warming. Rational management and improvement of these rangelands will not only increase their productivity to satisfy the growing need for feed for livestock, but will also allow them to act as a sink for CO2 and help in reducing the global warming.
According to the latest IPCC estimates, rangelands may play an important role in sequestering atmospheric CO2 (Allen-Diaz et al., 1996). Based on research concerning organic matter, especially if conditions and productivity of overgrazed and desertified areas could be improved through effective management (Gilmanov, 1995,1997).
Various landscapes have been hypothesized as potential contributors to the "missing sink" including rangelands. The vast areas of grazing lands are believed to have a large potential to sequester carbon and mitigate the greenhouse effect. Although arid and semi-arid ecosystems are known to have substantially lower productivity than forests, it was hypothesized that the vast landscapes of Central Asia dominated by rangeland ecosystem could be an important contributor to the "missing sink"(Nasyrov, 2000). Thus, the main objective of the special project was (GL-CRSP, Livestock Development and Rangeland Conservation tools for Central Asia) to document the daily magnitudes and growing season dynamics of net ecosystem CO2 exchange (NEE) in representative rangelands of Kazakhstan, Uzbekistan, and Turkmenistan.
However, direct field measurements of the magnitude and dynamics of CO2 fluxes on rangelands of Central Asia have not been made. Therefore, a project that gathered interdisciplinary team of scientists from different international and national institutions included experimental measurements and mathematical modeling of net CO2 fluxes at three representative rangeland sites of Central Asia was initiated in 1998.
Continuous measurements of the diurnal and seasonal dynamics of CO2 exchange were obtained at three sites in Central Asia. Field stations, such as the Bowen Ratio/Energy Balance (CO2/BREB) system manufactured by Campbell Scientific (Model 023) for the measurement of CO2 flux, energy balance, and related micro-meteorological characteristics, were established at the beginning of the 1998 growing season at three sites, which characterized representative rangelands of Central Asia. These included: typical steppe, Shortandy site, Kazakhstan; sagebrush-ephemeroidal semidesert, Karnap site, Uzbekistan; and shrub sandy desert, Karrykul site, Turkmenistan.
The main aim of the project was to determine the role of rangelands of Central Asia in the global carbon cycle, and to test the utility of carbon dioxide flux technology for assessing the productivity of the various rangeland ecosystems. Flux refers to the net movement of CO2 back and forth between the surface (soil and plants) and the atmosphere.
Field data for CO2 fluxes and associated micro-meteorological characteristics were collected continuously at 20-minute intervals. These data were routinely transferred electronically to Nickanor Z.Saliendra of the Forage and Range Research lab, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Logan, Utah, for processing into five-day segments.
The segmented data sets were subsequently used to calculate daily integrals of CO2 flux. These data were analyzed by T.G. Gilmanov at South Dakota State University to evaluate the relationships between micro-meteorological characteristics and rates of CO2 flux.
The obtained results indicated that net growing season CO2 fluxes were positive at all three rangeland monitoring sites in Central Asia with a daily and seasonal flux as for the typical steppe of northern Kazakhstan sequestered 328 g CO2/m2/season, which is equivalent to 89 g C/m2. The sagebrush-ephemeroidal semidesert site at Karnap, Uzbekistan sequestered 698 g CO2/m2/season. The shrub sandy desert at Karrykul in Turkmenistan sequestered 175 g CO2/m2/season.
Given the vast area of rangelands, this rate of carbon assimilation can turn Central Asian rangelands into a significant CO2 storage sink, and they can greatly contribute to reducing the global warming trend. This makes the rehabilitation and management of Central Asian rangelands all the more important. As a result, rangelands in Central Asia appear to play an important role in the sequestration of carbon.
Several years of field and laboratory experiments have shown the suitability of Bowen Ratio techniques for rangeland conditions in Central Asia.
In addition to these results, the project also provided a spin-off in terms of the human resource development. Scientists from all the measurement sites in Central Asia are now able to maintain and fully operate the Bowen Ratio system and could be considered as capable partners for future joint international projects in Central Asia.
FURTHER STEPS...
As a matter of course, the serious problems raised by environmental management and regional sustainable development lie eventually in the hands of policy makers. Their action must be based on a sound physical and socio-economic scientific expertise, which requires both a disciplinary and interdisciplinary approach within an integrated environmental scope, the so-called IEA "Integrated Environmental Assessment."
In order to contribute to food security, poverty alleviation, and environmental protection in Central Asian region and other drylands region one needs to:
Increase production, household income and welfare
Conserve or arrest degradation of natural resources
Assess current status of agroecosystems and combined impact of technologies on ecological changes and the efficiency with which resources are used for increasing human living standard at the levels of farm and collection of farms, village and a landscape.
Site assessments should take into account a broad range of information that can help to understand processes of change and the actors that participate in these changes. A variety of ethnoscientific methods can be employed, including the reconstruction of landscape histories and interviewing of knowledgeable villagers.
The GIS and modeling methodologies are also the only available way to integrate vast amounts of available data on drylands (soil, vegetation, climate, population) with new approaches to provide managers and decision-makers at the local and regional scales an adequate tool to increase the productivity and ensure the sustainability of drylands to satisfy the needs of the human population of the region.
The results of this assessment will help scientists understand trends in local biodiversity degradation and will provide ideas for their better management, and will also help identify particularly dynamic, resourceful, and resilient components of the village.
ACKNOWLEDGMENTS
The author grateful to the Global Livestock Collaborative Research Support Program (GL-CRSP) for supporting the project, Livestock Development and Rangeland Conservation tools (LDRCT) for Central Asia.
Supervisory work of Drs. D.A. Johnson and N.Z. Sliendra from Forage and Range Research lab. ARS-USDA, Utah, Logan and Dr. Dennis Ojima, NREL, Colorado State University, Fort Collins, Colorado as well as the assistance of Drs.B.K.Mardonov and T.H.Mukimov for data gathering and their initial processing are highly appreciated.
The draft of paper was prepared during Dr. M. Nasyrov's Visiting Scientist Award program funded by START.
REFERENCES
1. Allen-Diaz, B. et. al. (1996). Rangelands in a changing climate: Impacts, adaptations and mitigation, Climate change 1995. Impacts, adaptations and mitigation of climate change. Scientific-Technical Analyses. Contribution of working group II to the Second Assessment Report of the IPCC.Cambridge University Press, pp.131-158.
2. Beniwal S.P.S. and Varma S. (2000). Transforming Agriculture in Central Asia and the Caucasus: The role of ICARDA. ICARDA Caravan. pp.8-9.
3. Gilmanov, T.G. (1995). The state of rangeland resources in the newly Independent States of the former USSR. P. 10-13. In: N.E.West (ed.), Fifth International Rangeland Congress, Salt Lake City, Utah.
4. Gilmanov, T.G. (1997). Ecology of rangelands of Central Asia and modeling of their primary productivity. P. 147-178. In: Central Asia Livestock Regional Assessment Workshop.Tashkent, Uzbekistan, Feb.27-March 1, 1996. Davis, CA: Small Ruminant CRSP.
5. Gintzburger G., Toderich K.N., Mardonov, B.K. and Mahmudov M M. (2003). Rangelands of the arid and semi-arid zones in Uzbekistan. ICARDA-CIRAD 450 pp.
6. Nasyrov M.G. (2000). Global Warming and the Rangelands. ICARDA CARAVAN no.13 pp.1314.
