Abstract
Across savanna landscapes of southern Africa, people are strongly tied to the environment, meaning alterations to the landscape would impact livelihoods and socioecological development. Given the human–environment connection, it is essential to further our understanding of the drivers of savanna vegetation dynamics, and under increasing climate variability, to better understand the vegetation–climate relationship. Monthly time series of Advanced Very High-Resolution Radiometer (AVHRR)- and Moderate Resolution Imaging Spectroradiometer (MODIS) derived vegetation indices, available from as early as the 1980s, holds promise for the large-scale quantification of complex vegetation–climate dynamics and regional analyses of landscape change as related to global environmental changes. In this work, we employ time series based analyses to examine landscape-level vegetation greening patterns over time and across a significant precipitation gradient. In this study, we show that climate induced reductions in Normalized Difference Vegetation Index (NDVI; i.e., degradation or biomass decline) have had large spatial and temporal impacts across the Kwando, Okavango, and Zambezi catchments of southern Africa. We conclude that over time there have been alterations in the available soil moisture resulting from increases in temperature in every season. Such changes in the ecosystem dynamics of all three basins has led to system-wide changes in landscape greening patterns.
Highlights
Savanna landscapes, which cover about a fifth of the Earth’s surface, are representative of an intermittent ecosystem with a patchy mosaic composed of grasslands, scattered woody vegetation, and in some regions, closed woodland [1,2]
While precipitation is most commonly noted in the literature as the driving force of spatial heterogeneity across the landscape recent studies have emphasized the impact of temperature, in terms of constraining greening processes [19,20]
While both variables are highly influential in their own right, it is the cumulative impact of changing climate regimes that is driving landscape processes across savanna landscapes
Summary
Savanna landscapes, which cover about a fifth of the Earth’s surface, are representative of an intermittent ecosystem with a patchy mosaic composed of grasslands, scattered woody vegetation, and in some regions, closed woodland [1,2]. The authors of [6] illustrated that, globally, savanna function and drivers of spatial heterogeneity differ from continent to continent. There is consensus that the availability of resources (e.g., water, nutrients) and disturbance regimes (e.g., fire, herbivory) are the most important drivers regulating savanna vegetation [7]. In such complex ecosystems, further complicated by human utilization of the landscape, there are undoubtedly overlapping and/or interacting drivers of environmental change. A sound understanding of ecosystem variability and drivers of heterogeneity is needed, especially in savannas, which have long been deemed to exist in a non-equilibrium state
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