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The human–environment nexus and vegetation–rainfall sensitivity in tropical drylands

Abstract

Global climate change is projected to lead to an increase in both the areal extent and degree of aridity in the world’s drylands. At the same time, the majority of drylands are located in developing countries where high population densities and rapid population growth place additional pressure on the ecosystem. Thus, drylands are particularly vulnerable to environmental changes and large-scale environmental degradation. However, little is known about the long-term functional response of vegetation to such changes induced by the interplay of complex human–environmental interactions. Here we use time series of satellite data to show how vegetation productivity in relation to water availability, which is a major aspect of vegetation functioning in tropical drylands, has changed over the past two decades. In total, one-third of tropical dryland ecosystems show significant (P < 0.05) changes in vegetation–rainfall sensitivity with pronounced differences between regions and continents. We identify population as the main driver of negative changes, especially for developing countries. This is contrasted by positive changes in vegetation–rainfall sensitivity in richer countries, probably resulting from favourable climatic conditions and/or caused by an intensification and expansion of human land management. Our results highlight geographic and economic differences in the relationship between vegetation–rainfall sensitivity and associated drivers in tropical drylands, marking an important step towards the identification, understanding and mitigation of potential negative effects from a changing world on ecosystems and human well-being.

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Fig. 1: Significant positive and negative trends in vegetation–rainfall sensitivity (Mann–Kendall test, P < 0.05) across continents and their distribution per continent (and globally) in %.
Fig. 2: Main driver combinations of significant trends (Mann–Kendall test, P < 0.05) in vegetation–rainfall sensitivity per pixel at 0.25° spatial resolution.
Fig. 3: Driver combinations and contribution to changes in vegetation–rainfall sensitivity.
Fig. 4: Changes in ecosystem functioning in relation to economic strength.

Data availability

The datasets analysed in this study are publicly available as referenced within the article. The data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.

Code availability

The codes used in the data analysis to calculate SeRGS as well as potentially related drivers are available at https://github.com/Frangi10ne/SeRGS.

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Acknowledgements

This research is part of the project entitled title ‘Greening of drylands: Towards understanding ecosystem functioning changes, drivers and impacts on livelihoods’, which is financed by the Danish Council for Independent Research (DFF, Grant ID: DFF-6111‐00258). S.H. acknowledges the funding from the Belgian Federal Science Policy Office (Grant SR/00/339) and T.T. from the Swedish national Space board (SNSB Dnr 95/16). A.W.R.S. is partly funded on the ERC-2016-ADG HOPE project, W.D.K. on the eScience RETURN project, and A.M.A. was supported by the Swedish Research Council (Grant# 2018-00430).

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C.A., S.H., T.T. and R.F. designed the study. C.A. conducted the analyses with support from S.H., T.T., W.D.K., A.W.R.S. and A.M.A.; C.A. drafted the manuscript with contributions by all authors.

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Correspondence to Christin Abel.

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Abel, C., Horion, S., Tagesson, T. et al. The human–environment nexus and vegetation–rainfall sensitivity in tropical drylands. Nat Sustain 4, 25–32 (2021). https://doi.org/10.1038/s41893-020-00597-z

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