بررسی تغییرات کاربری اراضی و اثرهای آن بر فرسایش خاک در شهرستان مشکین‌شهر

فرسایش خاک از مهم‌ترین چالش‌های زیست‌محیطی است که تغییرات کاربری اراضی یکی از عوامل اصلی افرایش پتانسیل آن است. شهرستان مشکین‌شهر به‌دلیل ویژگی‌های محیطی از دیرباز تحت‌تاثیر وقوع فرسایش بوده و در طی سال‌های اخیر با توجه به رشد جمعیت و تغییرات غیراصولی، کاربری اراضی پتانسیل رخداد این مخاطره در‌سطح شهرستان افزایش یافته است. بر این اساس، محققان در پژوهش حاضر به‌دنبال ارزیابی اثر تغییرات کاربری اراضی بر فرسایش خاک در شهرستان مشکین‌شهر هستند. در راستای دستیابی به هدف‌های پژوهش نقشۀ کاربری اراضی با استفاده از روش شیءمبنا برای دو سال 2002 و 2024 استخراج و در مرحلۀ بعد لایه‌های اطلاعاتی سایر عوامل موثر بر فرسایش در محیط سیستم اطلاعات جغرافیایی تهیه شد. در‌نهایت، برای پهنه‌بندی خطر فرسایش، استانداردسازی لایه‌ها با استفاده از تابع فازی، وزن‌دهی معیارها با بهره‌گیری از روش کریتیک و مدل‌سازی با استفاده از الگوریتم چندمعیارۀ ویکور صورت پذیرفت. براساس نتایج حاصل از تحلیل تغییرات کاربری اراضی در هر دو دورۀ زمانی مطالعه‌شده کاربری‌های مراتع ضعیف و زراعت دیم بیشترین مساحت شهرستان را پوشش می‌دهند. با نظر به نقشۀ پهنه‌‌بندی فرسایش نیز در سال 2002 مساحت طبقۀ بسیار پرخطر و پرخطر 88/10 و 55/26درصد بوده است که مقدار این طبقات خطر در سال 2024 به‌ترتیب به 14/14 و 33/27 درصد افزایش یافته است. به‌طور کلی، با توجه به نتایج پژوهش می‌توان کاهش سطح مراتع، باغ‌ها و پوشش جنگلی و در‌مقابل افزایش کاربری‌های زراعی (آبی و دیم) و مسکونی را از دلایل اصلی افزایش پتانسیل فرسایش خاک شهرستان مشکین‌شهر دانست.

investigating land use changes and their effects on soil erosion in meshkinshahr county

abstractsoil erosion represents a critical environmental challenge, with land use changes being the primary factors that exacerbate its potential. meshkinshahr county has long been susceptible to erosion due to its environmental characteristics, while population growth and unprincipled land use changes have further heightened this risk at the county level in recent years. this study aims to evaluate the impact of land use changes on soil erosion in meshkinshahr county. to achieve the research objectives, land use maps for the years 2002 and 2024 were generated using an object-oriented approach. subsequently, additional layers of factors influencing erosion were prepared using geographic information systems (gis). erosion zoning was then conducted by standardizing these layers with a fuzzy function, weighting the criteria using the critic method, and modeling with the vikor multi-criteria decision-making algorithm. the analysis of land use changes revealed that, in both time periods, poor pastures and dryland agriculture occupied the largest areas within the county. according to the erosion zoning map, in 2002, the areas classified as very high-risk and high-risk constituted 10.88 and 26.55%, respectively. by 2024, these figures increased to 14.14 and 27.33%. overall, the study indicated that the reduction of pastures, gardens, and forest cover combined with the increase in agricultural (both irrigated and dryland) and residential land uses were the primary drivers behind the heightened potential for soil erosion in the county. keywords: land use, erosion, object-based method, multi-criteria analysis. introductionsoil is one of a country’s most vital natural resources and erosion is a significant factor contributing to the degradation and loss of soil fertility (motamedirad et al., 2023, p. 147). in recent years, ongoing changes in land use driven by the need to meet the diverse demands of the growing global population have become a crucial aspect of environmental change (taloor et al., 2020, p. 38; qingge et al., 2020, p. 147; hussain et al., 2020, p. 2). inadequate management practices related to land use changes can exacerbate adverse effects on soil properties, increasing its vulnerability to erosion (samie et al., 2022, p. 60; costea et al., 2022, p. 2). meshkinshahr county has long been susceptible to erosion due to its environmental characteristics. recently, however, population growth and unprincipled land use changes have heightened the risk of this hazard at the county level. therefore, this study aimed to evaluate the impact of land use changes on soil erosion in meshkinshahr county. materials & methodsin this study, we investigated land use changes by utilizing landsat satellite images from the us geological survey, specifically from the oli-tm sensors for the years 2002 and 2024. to prepare these images, we applied geometric and atmospheric corrections using envi 5.3 software. next, we extracted land use maps for the two study periods by employing an object-based classification method and the nearest neighbor algorithm in ecognition software. following this, we identified the factors influencing erosion in the region, which included land use, slope, lithology, soil type, distance from communication roads, distance from rivers, and precipitation. information layers were prepared for each criterion in the geographic information system (gis). the evaluation and standardization of these layers were conducted using the fuzzy membership function and the criteria were weighted using the critic method. finally, the analysis and modeling were carried out using the vikor multi-criteria analysis method. research findingsthe analysis of land use changes revealed that, in both study periods, poor pastures and rainfed agriculture accounted for the largest areas within the county. conversely, irrigated lands and snow-covered areas represented the smallest portions of the total county area in both 2002 and 2024. throughout the study period, there was an increase in irrigated agriculture, rainfed agriculture, and residential areas, while the extent of gardens, forested lands, good pastures, poor pastures, and snow-covered lands had decreased. notably, the most significant land use change in the county was the conversion of poor pastures to rainfed agriculture. by 2024, approximately 452.02 km2 of poor pastureland had been converted to rainfed agriculture compared to 2002.in terms of the weight coefficients of the criteria, in 2002, the most influential factors were slope, land use, lithology, and soil; while in 2024, the order had shifted slightly to land use, slope, lithology, and soil. according to the erosion zoning map, in 2002, the areas classified as very high-risk and high-risk had encompassed 422.14 and 1,030.03 km2, respectively. by 2024, these figures had increased to 548.58 and 1,060.36 km2. furthermore, the erosion maps for both study periods indicated that the areas classified as very high-risk and high-risk were predominantly located within agricultural zones (both rainfed and irrigated), as well as in poor pastures and residential areas. discussion of results & conclusionthe results indicated that meshkinshahr county exhibited a very high potential for erosion due to various environmental factors, including loose soils, sensitive and erodible formations, steep slopes, significant rainfall, and the presence of numerous waterways. moreover, the decline in both good and poor pasture areas, alongside reductions in orchards and forest cover, had exacerbated the potential for soil erosion as agricultural land use (both irrigated and dryland) and residential developments had increased. in light of these findings, several recommendations are proposed to manage land in accordance with sustainable development principles. these include converting low-yield rainfed lands into forage and medicinal plant areas, strengthening and restoring rangeland vegetation, preventing overgrazing, and alleviating the pressure on rangelands by creating alternative job opportunities. additionally, raising public awareness about the consequences of unsustainable land use practices, delegating the management of rainfed lands to local communities, and educating farmers on conservation measures are crucial emergency actions to protect and sustainably utilize water and soil resources. it is anticipated that the land use change map and erosion risk zoning map generated in this study will serve as valuable resources for managers and planners. these tools will provide essential insights into the status of land use changes and soil erosion potential in the county, facilitating the implementation of effective control and management measures to mitigate erosion in high-risk areas.