Assessment of the long-term effects of climate on vegetation in 25 watersheds in dry and semi-dry areas, Algeria

It is necessary to understand vegetation evolution and its sensitivity to the global climate, particularly with regard to ecosystems and environmental balance. 25 watersheds were selected in Algeria for this study. Here, the vegetation index (NDVI) and climatic variables (precipitation and temperature) were used to verify the temporal-spatial patterns and impact of the time difference from 1981 to 2021 by applying the correlation coefficient and time delay analysis. The NDVI showed a significant decline, especially in recent years, and spatial differences in NDVI in all areas of study were narrow (slope values from 0.0005 to 0.04), decrease in surface water area from year to year was observed in all regions. The vegetation index was negatively associated with low rainfall and high temperatures. The vegetation's reaction to temperature has been greater than that too rainfall. In general, a time lag in the vegetation response was found over a time period of at least 1 month. This study provided new insights into variations in vegetation change and the importance of vegetation recovery.