Time Series Analysis of Land Cover Change in Dry Mountains: Insights from the Tajik Pamirs

Abstract

Greening and browning trends in vegetation have been observed in many regions of the world in recent decades. However, few studies focused on dry mountains. Here, we analyze trends of land cover change in the Western Pamirs, Tajikistan. We aim to gain a deeper understanding of these changes and thus improve remote sensing studies in dry mountainous areas. The study area is characterized by a complex set of attributes, making it a prime example for this purpose. We used generalized additive mixed models for the trend estimation of a 32-year Landsat time series (1988–2020) of the modified soil adjusted vegetation index, vegetation data, and environmental and socio-demographic data. With this approach, we were able to cope with the typical challenges that occur in the remote sensing analysis of dry and mountainous areas, including background noise and irregular data. We found that greening and browning trends coexist and that they vary according to the land cover class, topography, and geographical distribution. Greening was detected predominantly in agricultural and forestry areas, indicating direct anthropogenic drivers of change. At other sites, greening corresponds well with increasing temperature. Browning was frequently linked to disastrous events, which are promoted by increasing temperatures.

The Spatiotemporal Change in Land Cover and Discrepancies within Different Countries on the Qinghai–Tibet Plateau over a Recent 30-Year Period

“…Furthermore, increased population and economic activities have accelerated the conversion of forest and agricultural land to pasture, construction land, and horticultural land in the area [35]. Grassland expansion and degradation coexist in the western Pamirs of Tajikistan, where grassland expansion is dominant [36]. Although some studies [15,18] have analyzed spatiotemporal changes in land cover on the Qinghai-Tibet Plateau through long-term series data, investigations that compare spatiotemporal characteristics of land cover change across the whole plateau as well as in different countries within the plateau are relatively lacking.…”