پایش تغییرات پوشش سطح زمین در راستای تخریب سرزمین (Modis Land Cover Product 2001-2013): محدوده‌ی جغرافیایی استان ایلام

مسئله ی تخریب سرزمین یکی از مهم ترین مشکلات زیست محیطی در سراسر جهان است. روش مطالعه بر پایه مطالعات میدانی و تجزیه و تحلیل تولیدات (mcd12q1)modis landcover-500m از سال 2001 تا 2013 با هدف پایش تغییرات پوشش سطح زمین در‌ راستای تخریب سرزمین در استان ایلام صورت گرفته است. نتایج نشان می‌دهد که (کد‌های2، 3، 4، 11، 14 و 255)، در طول دوره زمانی 13 ساله در محدوده مورد مطالعه هیچ پیکسلی به خود اختصاص نداده‌اند. همچنین (کد های1، 5، 6، 8 و 9) در کل دوره حداقل مقادیر سطوح پوششی و پیکسلی یعنی به ترتیب 3، 6، 36، 23 و 13 پیکسل به خود اختصاص داده‌اند. همچنین سطوح آبی (کد صفر) در محدوده مورد مطالعه از سال 2001 تا 2013 دستخوش تغییرات افزایشی بسیار کمی بوده است. سطوح مربوط به مناطق شهری و مسکونی (کد13) هیچگونه تغییری در آن مشاهده نشد. در نهایت کدهای (7و10و12و15) به ترتیب هر کدام 564424، 8953، 47030 و443520 پیکسل یعنی 99.78 درصد از سطح منطقه را پوشش داده‌اند. به طوری که جنگل‌های درختچه‌ای باز با مقدار 564424 پیکسل و مناطق فاقد پوشش‌گیاهی با 443520 پیکسل، بیشترین مقدار پوشش سطح زمین را در منطقه به خود اختصاص داده‌اند. به طورکلی روند تغییرات سطوح بدون پوشش‌گیاهی در طول 13 سال یک روند افزایشی را نشان می‌دهد. و این می‌تواند یک موضوع نگران کننده به لحاظ تخریب سرزمین ‌باشد. که باید با جدیت مورد توجه قرار گیرد. در مقابل روند تغییرات پهنه‌های جنگلی درختچه‌های باز در طول دوره مورد مطالعه یک روند کاهشی (وسعت 53%) را نشان می‌دهد. که در مقایسه با روند افزایشی سطوح فاقد پوشش‌گیاهی (41.60%) یعنی تخریب سرزمین در منطقه صورت گرفته است.

Monitoring land cover changes in line with land degradation (MODIS land cover croduct 2001-2013): Ilam province geographical range

IntroductionLand degradation is a global challenge that results in reduced soil fertility and eventually becomes one of the major environmental issues worldwide. The issue of land use and land cover changes by mankind is one of the most important factors of environmental change at the local and global scale which has significant implications for ecosystem health, water quality and sustainable land management (Foley et al., 2005; Lubchenco, 1998). The problem of land degradation in the Ilam province is affected by a combination of natural and anthropogenic factors, including deforestation, drought, overgrazing, intensive agriculture, increased sediment performance due to soil erosion, evaporation, dam construction and drought. These environmental problems are ultimately linked to changes in land cover and land use. Therefore, it is important to consider land cover and landuse changes to monitor environmental changes and sustainable resource management plans for fragile ecosystems such as Ilam province and provide results to area managers and planners for restoration and prevention.Materials and methodsIn this study, we used MODIS Terra Satellite Land Cover Products (MCD12Q1) to study the monitoring of land cover changes in the Ilam province for the period of 2001 to 2013. All data for the study area were mosaicked and sampled with the UTM Global Coordinate System, using the nearest neighbor sampling method. Then they were Georeferenced and finally, on GisEnvi software correction operations (geometric, radiometric and atmospheric) were run and then the study area was clipped. The method initially classified the images into 17 classes and then calculated the number of pixels (zeros up to 255) of each class for the duration of 13 years and mapped the trends and percentages of changes occurring to each class.Results and discussionShrub forests have begun to grow in size since 2009 and their numbers appear to have increased in the coming years. Conversely, forestsavannahs and savannas in 20012007 had a small area (34 pixels in total) of their own, and since 2007 species of this type have become extinct and are not observed at all, in the studied level. The water levels (code zero) in the study area underwent very little change from 2001 to 2013, and only from 2004 to 2008 did the extent of the water levels show greater values than other years. The maximum amount of water in 2005 was 29 pixels (that means, 7250000 m = 500*500*29), which is mostly related to the Karkheh and several pixels of the Simare River in the south and east of the border. But water levels appear to have increased since 2013 due to the construction of several dams in the study area. Also, the levels for urban and residential areas (Code 13) from 2001 to 2013 are consistently 159 pixels per year across the study area, and we don’t see any increase or decrease in it. Finally (code 7, 10, 12 and 15), respectively, each are 564.424 and 8.953 and 47.030 and 443.520 pixels for 13 years. That is %99.78 of the area covered. Among these areas, open forest shrubs with 564,424 pixels and no vegetation areas with 443,520 pixels had the highest amount of land cover (%94.5) in the area.ConclusionAccording to the extracted map (Map No. 2) the story lacking vegetation named Code 15 which is marked yellow in the map, is mostly located in the west and southwest of the study area, including the lowland basins, namely Western Abbas plain, Eastern Abbas plain, Chenane, Abadan, Mehran, Dehloran, Salehabad, and Sumar. In some years, due to the increasing trend of land degradation, it is advancing toward the center and east of the region. Overall, the trend of changes in the amount of no vegetation levels over the past 13 years show an increase, and this can be a concerning issue in terms of land degradation. This should be seriously taken into consideration. As the maps show, there is a decreasing inclination in the trend of open shrub forest zones during the study period as well.