Quantitative assessment of 2014–2015 land-cover changes in Azerbaijan using object-based classification of LANDSAT-8 timeseries

Abstract

The main goals of this study are the object-based land-cover classification of LANDSAT-8 satellite imagery of 2014 and 2015, the quantitative assessment of gross and net changes of agricultural land, built-up areas, forest, bare soil and forest between 2014 and 2015, the quantification of the Normalized Difference Vegetation Index (NDVI) rates within these land-cover classes, and the change detection analysis between the NDVIs. The achieved overall accuracies of object-based classification for the 2014 and the 2015 land-cover maps were 82 and 87 %, respectively. Therefore, the achieved accuracies were considered to be acceptable for quantified change detection analyses. For the gross areas of agricultural land, forest and built-up areas an increase was observed. The agricultural gross area was 30,911 km2 in 2014 and 31,999 km2 in 2015. The gross area of the built-up land increased from 12,550 to 13,548 km2. The gross area of forest land changed from 8211 to 9175 km2. A decrease was observed in the gross area of grassland from 28,229 to 24,925 km2. This was primarily related to the land-cover shifts driven by agricultural activities. The gross areas of bare soil and water bodies did not change significantly. The net change analysis, however, revealed significant differences in comparison to gross change areas for both gains and losses of the land-cover classes. The net change analysis revealed positive net changes of 7229, 5576, 1337, 399, 951 km2 for agricultural land, forest, built-up areas, bare soil and water bodies, correspondingly. A negative net change of 2198 km2 was observed for grassland. This allows to conclude that the negative net change of grassland was related with the significant changes of grassland into agricultural land. No significant net changes were observed for the bare soil land-cover class. The classification of NDVIs derived from 2014 to 2015 LANDSAT-8 OLI satellite images showed that the vegetation cover of agricultural and built-up land-cover increased for the low (0.1–0.2) and medium (0.2–0.3) and decreased for the high NDVI values (0.3–1). The area of high (0.3–1) NDVIs in the forest land-cover was observed to be higher in 2015 than in 2014. A reduction in the low (0.1–0.2), medium (0.2–0.3) and high NDVI values (0.3–1) was observed for the grasslands land-cover. The reductions of the high NDVI rates (0.3–1) observed for agricultural, build-up and grasslands land-cover types may be related to agricultural and industrial activities and also to climate change impacts. For the entire coverage of Azerbaijan, positive and negative NDVI changes of 3170 and 3859 km2 respectively were observed.