Environmental Erosion Research

fa مدل ایرانی ارزیابی پدیده‌ی بیابان‌زایی برای توسعه‌ی پایدار منطقه‌ای An Iranian Model of Desertification Potential Assessment for Sustainable Regional Development روشهای نوین و دقیق در تهیّه نقشه فرسایش (سنجش از دور و سیستم‌های اطلاعات جغرافیایی) مستخرج از پایان‌نامه / رساله / طرح پژوهشی در حال حاضر بیابان‌زایی مشکلی گریبان‌گیر برای بسیاری از کشور‌ها به ویژه کشور‌های در حال توسعه است. شناخت مناطقی که در معرض پدیدهی بیابان‌زایی قرار دارند و آگاهی از فرایند‌ها و روش‌های مدیریتی مناسب، برای مبارزه با این پدیده و جلوگیری از گسترش آن اهمیت فراوانی دارد. لذا در این پژوهش برای تهیهی اطلس بیابان‌زایی ایران، از مدل ایرانی ارزیابی وضع موجود بیابانزایی (IMDPA) استفاده شد. در این مدل با استفاده از تجارب جهانی و مدل‌های بین‌المللی همچنین مدل‌های رایج در کشور، معیارهای اقلیم، زمین‌شناسی، خاک، پوشش گیاهی، آب، فرسایش، اقتصادی- اجتماعی و تکنولوژی و شاخص‌ها و زیرشاخص‌های تأثیر‌گذار در بیابان‌زایی شناسایی شد. سپس با در نظر گرفتن این معیارها و شاخص‌ها و با کمی کردن آنها در مناطق خشک، نیمه‌خشک و خشک نیمه‌مرطوب، نقشهی شدت بیابانزایی تهیه شد؛ به گونهای ‌که نتایج حاصل از برآورد این مدل در مقیاس کشور نشان داد که در شرایط موجود 73/ 88 درصد از مساحت کشور معادل 6/ 143365238 هکتار، تحتتأثیر پدیدهی بیابان‌زایی قرار دارد. از مساحت کل کشور، سطحی بالغ بر 3/49425703 هکتار معادل 59/30 درصد کل کشور در کلاس بیابان‌زایی کم، مساحتی بالغ بر 6/ 93567913 هکتار معادل 91/57 درصد در کلاس II یا متوسط و سطحی حدود 8/371621 هکتار معادل 23/0 در صد در کلاس III یا شدید قرار می‌گیرد. همچنین کلاس IV بیابان‌زایی یا وضعیت بسیار شدید بیابان‌زایی با توجه به چارچوب محاسباتی مدل (IMDPA)، تحتتأثیر معیارهای هشت‌گانه حذف شده و عملاً مناطق کویرهای طبیعی که سطح آنها معادل 3/ 15624274 هکتار یا 67/9 درصد سطح کشور است، فراتر از این کلاس قرار دارد.   <div dir="RTL">Extended abstract 1-Introduction Desertification means land degradation in the arid, semi-arid and dry sub-humid regions because of natural or anthropogenic factors. Desertification is accounted as the third most important global challenge after the crisis of water shortage and drought in the 21st century. Desertification is a problem for many countries, especially the developing countries. Identifying the regions exposed to desertification is so important for combating desertification and leads to better planning. Also the awareness of inappropriate management practices can reduce the intensity of this phenomenon, and prevent its development. There are many models for preparing desertification maps in the world that the most common of which includes UNEP-FAO, ASSOD, GLASSOD, LADA, and MEDALUS. Also in Iran ICD, MICD and recently, IMDPA models have been presented. IMDPA model includes some criteria affecting desertification, and some indicators for the quantitative assessment of the criteria. In this research IMDPA model was used for the assessment of Iranian desertification condition. 2-Methodology IMDPA model have 8 criteria which are called desertification criteria and their indicators are used for quantifying them. At first 130 indicators were selected for all 9 criteria but on the one hand it wasn’t possible to prepare information of all of them for the whole of country and on the other hand it was costly and time consuming. So for each criterion, up to 4 key indicators were identified. Indicators related to each criterion are as follows: <ul> <li dir="LTR">Climate: drought, aridity index, rainfall amount.</li> <li dir="LTR">Geomorphology: land use, rock sensitivity and physiography.</li> <li dir="LTR">Water: negative balance of water, groundwater depletion, EC and SAR.</li> <li dir="LTR">Soil: EC, texture, depth, gravel percentage.</li> <li dir="LTR">Vegetation cover: coverage status, coverage utilization and vegetation cover rehabilitation.</li> <li dir="LTR">Erosion: water erosion (vegetation cover density, land use and water erosion density and type) and wind erosion (days with dust storm index, vegetation cover, non-living cover density and erosion faces appearance).</li> <li dir="LTR">Socio-economic: socio-cultural factors, organization and participation, awareness, experience and native knowledge.</li> </ul> </div>   <ul> <li>Urban or technology development: mine and road density, converting forests and rangelands to urban and industrial areas, improper agriculture, converting garden lands to residential-industrial regions and amount of green space per person.</li> </ul> In this study each index received a weight (1 to 4) according to expert opinions and each criterion was obtained based on its indicators’ geometric mean according to the formula below:   <img alt="" height="26" src="file:///C:/Users/EcoMan/AppData/Local/Temp/msohtmlclip1/01/clip_image002.png" width="420" >                                                                 Index X: each criterion Layer: indicators related to each criterion N: number of indicators related to each criterion Weighted averages of indicators related to each criterion were determined and finally desertification intensity was gained based on the geometric mean of all criteria according to the formula below:   <img alt="" height="22" src="file:///C:/Users/EcoMan/AppData/Local/Temp/msohtmlclip1/01/clip_image004.png" width="532" >               Then, final map of desertification intensity was determined using different layers and obtained maps related to each criterion and combination of layers and maps. So, the map of each criterion status was obtained from its own indicators. These maps can be used for the study of each index quality and its effect on desertification.  3- Results 3-1-Map of water and irrigation criterion The result of the quantitative value of this criterion that was determined using its indicators is shown in Figure (2). The zoning map of Iran plains based on Q3 is shown in Figure (3). Also this calculation result is shown in Table (2).  3-2-Map of vegetation cover criterion The map of Iran’s desertification condition based on vegetation cover or Q5 is shown in Figure (4). Table (3) shows all of its information. Also the zoning map of Iran’s plains based on Q5 is shown in Figure (5). 3-3-Status quo of Iran’s desertification Finally, the intensity map of Iran’s desertification was prepared and the calculation was done in order to determine the classes of desertification (Table 4).   4-Discussion and conclusion In this research IMDPA model was used in order to prepare Atlas of Iran’s desertification. In this model, there are 8 criteria which are regarded as desertification criteria and their indicators are used for quantifying them. At first, 130 indicators were selected for all the 9 criteria but on the one hand it wasn’t possible to prepare the information of all of them for the entire country, and on the other hand, it was costly and time consuming. So for each criterion, up to 4 key indicators were identified. The desertification intensity map of Iran was determined using these criteria and indices, and also, they were quantified in the arid, semi-arid and sub-humid regions.  The results showed that 88.73% of the country surface was affected by desertification which is equal to 143365238.6 hectares. The surface of more than 49425703.3 hectares equal to 30.59% of the total surface of the country was in the low desertification class, the surface of more than 935677913.6 hectares equal to 57.91% was in class II or medium, and a surface about 371621.7 hectares equal to 0.23% was in class III or intense. Class IV of the desertification or very intense was omitted regarding to IMDPA model and the 8 criteria, and the natural desert areas whose surface was equal to 15624274.3 hectares or 9.67% were beyond this class. اطلس بیابان‌زایی, ایران, معیارها و شاخص‌ها, مدل IMDPA Atlas of desertification, Iran, Criteria and indices, IMDPA model 21 38 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-66-3&slc_lang=fa&sid=1 gholamreza zehtabian غلامرضا زهتابیان ghzehtab@ut.ac.ir 10031947532846005018 10031947532846005018 No university of Tehran دانشگاه تهران hassan khosravi حسن خسروی hakhosravi@ut.ac.ir 10031947532846005019 10031947532846005019 Yes university of Tehran دانشگاه تهران hamed eskandari damaneh حامد اسکندری دامنه hamed.eskandari69@gmail.com 10031947532846005020 10031947532846005020 No university of Tehran دانشگاه تهران azam abolhasani اعظم ابوالحسنی زرجوع azamabolhasani67@yahoo.com 10031947532846005021 10031947532846005021 No university of Tehran دانشگاه تهران