Vegetation landscape analysis due to land use changes on arid lands

摘要

Fast land use changes have strongly affected arid and semi-arid regions at a global scale, affecting food security of the inhabitants of these regions. This study evaluated the fragmentation degree in the Chihuahua's desert region of Mexico by using data from the Landsat TM sensor. Nine scenes, taken with Landsat TM5 sensor from the years 1990, 2000, and 2012, were used for the analysis. The coverage of seven land uses (grasslands, shrubland, croplands, sandy desert vegetation, forest, water bodies, and urban areas) was obtained under supervised classification techniques and the accuracy level was evaluated through the Kappa multi-varied discrete index. The classification showed a good reliance level having global accuracies of 93, 93.2 and 90.3% for the years 1990, 2000 and 2012, respectively. The fragmentation analysis showed an increase in the number of patches, an indicator of the ecosystem degradation process. The patches number increased from 8,354.23 in 1990 to 9,658.36 in 2000 and to 11,469 in 2012. Simpson and Shannon diversity indexes proved a clear fragmentation process. During the period of 1990-2012, grasslands were the most affected vegetation type with a reduction of 30.7% in its area. Such reduction was mainly attributed to invasions of shrubland communities and to an increase in cropland areas.