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

Kim André Vanselow,Cyrus Samimi,Harald Zandler

doi:10.3390/rs13193951

Kim André Vanselow, Cyrus Samimi + Show 1 more

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https://doi.org/10.3390/rs13193951

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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.

Highlights

Knowledge of land cover and vegetation dynamics is crucial for comprehending changes in ecosystem structure, functions, and services and for revealing the underlying drivers of change [1,2]
To contribute to research on these poorly studied regions, we focus on greening and browning trends in the Western Pamirs, a dry mountain area in Central Asia characterized by high biodiversity [48,49]
We investigate whether we are able to detect and quantify land cover changes in terms of greening and browning with remote sensing imagery, and if so, whether these changes possibly stand in relation to the development of temperature, precipitation, or population or livestock numbers

Summary

Introduction

Knowledge of land cover and vegetation dynamics is crucial for comprehending changes in ecosystem structure, functions, and services and for revealing the underlying drivers of change [1,2]. Other regions across the planet have attracted attention, such as the mid-latitudes [22]; the subtropics [23]; the tropics [24]; arid and semi-arid areas of the southern hemisphere [25]; and mountains—the Tibetan Plateau [26,27,28]. Anthropogenic factors, such as fertilization and irrigation, are the drivers with the highest impact on greening and by far outweigh the effect of climate change [4,13,29]

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