ارزیابی آسیب پذیری سیمای سرزمین ناشی از شبکه جاده‌ای در استان لرستان

جاده ها نقش مهمّی در آسیب پذیری بوم سازگان های طبیعی و پایداری آن ها دارند. هدف از پژوهش حاضر ارائه روش نظام مند برای ارزیابی آسیب‌پذیری بوم شناختی به منظور استفاده در فرایند مکان یابی و ارزیابی آثار محیط زیستی جاده ها است. در نوشتار پیش رو فرایند ارزیابی آسیب پذیری شامل پنج مرحله تعیین شاخص های ابعاد آسیب پذیری، محاسبه و نقشه سازی شاخص ها، استانداردسازی شاخص ها، تعیین آسیب پذیری و تحلیل آسیب پذیری بوم شناختی است. استان لرستان به دلیل دارابودن شرایط خاص بوم شناختی و وجود شبکه جاده ای مهم در انتقال کالا و مسافر به منزله منطقه مورد بررسی انتخاب شد. برای کمّی سازی سه بُعد آسیب‌پذیری بوم شناختی شامل حسّاسیت، درمعرض تنش بودن و ظرفیت سازگاری از شاخص‌های خردشدگی سیمای سرزمین ناشی از جاده، بُعد فراکتال، همسایگی سکونت گاهی، صدای جاده، فرسایش، شاخص موقعیّت جغرافیایی، شاخص اتّصالات سیمای سرزمین و درجه غالبیت استفاده شده است. نتایج حاصل نشان داد که بیشترین میزان استرس ناشی از جاده بر زیست گاه های درختزار در محدوده ای به مساحت 157270 هکتار، وارد می شود؛ همچنین مناطق با حسّاسیت بالا در حدود 795132 هکتار (28.1%) از سطح استان را به خود اختصاص می دهند؛ افزون براین، نتایج مدل آسیب پذیری نشان داد که از کلّ منطقه مورد بررسی مناطق با آسیب‌پذیری خیلی پایین، پایین، متوسّط، بالا و خیلی بالا به ترتیب 2.5%، 52%، 42.1%، 3.1% و 0.3% از سطح استان را به خود اختصاص می دهند. براساس این، حدود نیمی از منطقه مورد مطالعه در پژوهش حاضر از شدّت آسیب پذیری متوسّط به بالا برخوردار است که این امر اهمّیت پژوهش درزمینه ارزیابی آسیب‌پذیری بوم شناختی در بررسی های محیط زیستی طرح ها و پروژه‌های توسعه ای را ضروری می سازد.

Vulnerability Assessment of the Landscape Made by Road Network in Lorestan Province

Roads, as the main artificial linear structures in any landscape, have an important role in the vulnerability of natural ecosystems and their sustainability. The purpose of this research is to introduce a systematic method for ecological vulnerability assessment to be used in road site selection and environmental impact assessment procedure. Five steps of the vulnerability assessment are involved in this study; like determining the indices of vulnerability dimensions, calculating and mapping the indices, standardization of the indices, determining the vulnerability index and analysis of local variability. Lorestan province was selected as the case study due to its ecological properties and the presence of important road network to transfer goods and passengers. Indices like infrastructure fragmentation index, fractal dimension, residential neighborhood index, road traffic noise, erosion, topographic position index, and landscape connectivity index and dominance degree have been applied to quantify sensitivity, exposure and adaptive capacity as major components of the vulnerability. The findings show that the highest tension of road events is on the woodland habitat in 157270 ha. Besides, the regions with a high degree of sensitivity cover 28/1% (795132 ha) of the total study area. Wetland and temperate grassland habitats have the least adaptive capacity. Furthermore, the vulnerability classes in very low, low, moderate, high, and very high cover 2/5%, 52%, 42/1%, 3/1% and 0/3% of the total study area respectively. Therefore, approximately half of the province has the vulnerability degree in over average. This study showed the importance of the ecological vulnerability evaluation in environmental impact studies of development projects.Extended Abstract1 IntroductionDespite the positive impact of roads on economic development, the roads can impose negative effects such as fragmentation, islanding and loss of habitats as well as a variety of contaminants on natural ecosystems. Considering the pressure on natural ecosystems, the road construction or their development are unavoidable and the most important of sequence is to increase the vulnerability of ecosystems. Vulnerability assessment increases objectivity in identifying the effects of human activities on the environment. The concept of landscape vulnerability is one way to study the effects of the road on structure and function of landscape. Ecosystems that are more sensitive and susceptible to road stress have limited the ability to adapt. Lorestan Province is one of the important provinces that contains valuable Zagros habitats which has also been pursuing transport development programs in recent years. The aim of this study was to identify and select the parameters affecting the vulnerability in interactions between road and landscape in the Lorestan province. Developing a systematic method to assess ecological vulnerability was another purpose which can be used to evaluate the environmental impacts and assess road network.2Materials and MethodsThe initial stage of data preparation was started using maps of land use, digital elevation model, road network, vehicle traffic volume and meteorological information. Using these data, three dimensions of ecological vulnerability including exposure, sensitivity, and adaptation capacity were determined. Landscape fragmentation, fractal dimension, residential neighborhood, and road traffic noise, as the indicators of exposure dimension, and the erosion topographic, position as sensitivity indicators, and indices of land surface connectivity and degree of dominance was used to calculate the adaptation capacity. Indicator maps were standardized to the same units to be used in the ecological vulnerability model. The map of three main dimensions of exposure, sensitivity and adaptation capacity were aggregated leading to create a map the ecological vulnerability.3Results and DiscussionBased on the results of the vulnerability model implementation using exposure maps, sensitivity and adaptive capacity, 2.5% of the study area had very low vulnerability level, about 51.7% low vulnerability, 42% moderate vulnerability, 3.2% severe vulnerability and 0.1% very severe vulnerability. Habitat fragmentation, residential proximity and road noise are in low level of intensity due to conformity to the roads network location and residential areas in the southeast and northwest of study area. Fractal dimension index is more intense in residential areas than other study area. The survey of the distribution of high severity class across the province showed that Khorramabad County with 32.7% had the highest value compared to other counties. Most of the environmentally sensitive areas that are most vulnerable are the Oshtrankuh Protected Area with an area of 18.8 km2, which is only 0.2% compared with the total area under the management of the EPA. Considering the high percentage of the study area with high sensitivity level, the road network analysis shows that approximately 1250 km (50.8%) of the total 2461 km of roads in this study, is in the high sensitivity level. In this study, vulnerability assessment quantification was done based on natural and manmade parameters related to the presence or absence of road network in Lorestan Province as the study area. Considering transportation network from EIA view point leads to select less indicators in comparison to previous studies. Based on this study, urban and rural areas, agricultural land and roadsides have most vulnerability degree. Fractal dimension, habitat fragmentation, traffic noise and distance from residential areas are most important pressure factors to natural habitat patches. In combination of exposure, sensitivity and adaptive capacity as vulnerability elements, the areas with high pressure are classified as most vulnerable and two others parameters have the least effect.4ConclusionThe findings from the study show indifferent condition of vulnerability in the study area. The pressure severity from roads and residential areas on natural resources is in converse with distance. Approaching natural areas, there is the potential pressure due to fractal dimension and border effect. In this study, habitat size is defined as most important booster of pressure on natural ecosystems. Therefore, wetland habitats suffer most stress due to their low area which makes them be unsuitable. Furthermore, the 75% of study area has high sensitivity because of its intrinsic essence as Zagross mountainous partial.