Spatiotemporal Analysis of Drought and Vegetation Changes in Northern Afghanistan (2000–2023)

تحلیل زمانی–مکانی خشکسالی و تغییرات پوشش گیاهی در شمال افغانستان (۲۰۰۰–۲۰۲۳)

Abstract

Drought in northern Afghanistan is associated with declining water availability, reduced agricultural production, and pressure on rural livelihoods. However, the scarcity of regular ground observations complicates long-term monitoring. This study analyzed the spatiotemporal patterns of drought and vegetation change across Balkh, Jawzjan, Sar-e Pol, and Samangan provinces from 2000 to 2023. Monthly standardized precipitation evapotranspiration index (SPEI) data at 1-, 3-, 6-, and 12-month accumulation scales and 16-day enhanced vegetation index (EVI) observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) were processed in Google Earth Engine and the Arc Geographic Information System (ArcGIS). For interannual comparison, regional annual means were computed, and relationships were evaluated with Pearson’s correlation coefficient (r) across 24 paired years using two-tailed probability values (p). Drought patterns differed by accumulation scale: short-term SPEI emphasized monthly variability, whereas 6- and 12-month SPEI more clearly represented event persistence. The years 2001, 2008, 2011, 2018, and 2021 were prominent dry periods at multiple scales. Long-term spatial patterns indicated relatively drier conditions in Jawzjan, northern Balkh, and northwestern Sar-e Pol, and relatively wetter conditions in Samangan and the southern parts of the study area. Strong vegetation cover occupied only a small proportion of the region, with the lowest EVI values in 2001 and 2008. All EVI–SPEI correlations were positive but statistically nonsignificant; the largest coefficient occurred for the 12-month SPEI (r = 0.213, p = 0.317). Some dry years coincided with reduced EVI, but the analysis did not establish a causal or uniform vegetation response to drought. The findings highlight the need for seasonal and lagged analyses, field validation, and explicit separation of irrigation and land-use effects.