NDVI and Land Cover Change Analysis Using MODIS data in Tunisia

Abstract:

Desertification has been one of the global problems in respect of society, economy, and environment. However its cause and effect is diverse and complex, and yet not clearly identified. In order to understand and control desertification, monitoring using satellite images is a major and fundamental part. This study therefore aims to conduct time series analyses for Normalized Difference Vegetation Index (NDVI) and land cover change, and to analyse their area distribution between two different years targeted in Tunisia. NDVI and land cover map are obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), which includes 17 land cover types. First, the time series analysis was conducted every three years from 2002 to 2011. Second, we compared area distribution of NDVI and land cover between 2002 and 2011. We defined that there was ‘severe’ desertification if NDVI was under 0.24 and classified the severe area within the two images respectively. The extracted area undergone severe desertification in 2011 was then overlaid on the NDVI map of 2002 to see the change. Barren or sparsely vegetated area of 2011 was also extracted first and overlaid on the land cover map of 2002 to observe how the land cover type had been changed from the past. It is estimated that desertification has been expanded in Tunisia as low NDVI value increases and barren or sparsely vegetated area expands while water or forest area decreases. In addition, the NDVI value of 2002 was higher and there was a little distribution of barren and sparsely vegetated area compared to 2011. Based on the result, this study is useful to realize the current state of affairs and the necessity of land planning in Tunisia. The result of the study is expected to be used to cope with desertification and land degradation, and further provides base data for establishing policies. This study was carried out with the support of ‘Forest Science & Technology Projects (Project No. S211214L030320)’ provided by Korea Forest Service.