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.
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
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.
The codes used in the data analysis to calculate SeRGS as well as potentially related drivers are available at https://github.com/Frangi10ne/SeRGS.
Environment Management Group Global Drylands: A UN System-Wide Response (UN Department of Environment Management, 2011).
Gudka, M. et al. Conserving dryland biodiversity: a future vision of sustainable dryland development. Biodiversity 15, 143–147 (2014).
Millennium Ecosystem Assessment Ecosystems and Human Well-Being: Desertification Synthesis (World Resources Institute, 2005).
Cherlet, M. et al. World Atlas of Desertification (Publication Office of the European Union, 2018).
IPCC Special Report on Climate Change and Land (eds Shukla, P. R. et al.) (IPCC, 2019).
Ji, F., Wu, Z., Huang, J. & Chassignet, E. P. Evolution of land surface air temperature trend. Nat. Clim. Change 4, 462–466 (2014).
Huang, J., Guan, X. & Ji, F. Enhanced cold-season warming in semi-arid regions. Atmos. Chem. Phys. 12, 5391–5398 (2012).
Zhang, W., Brandt, M., Tong, X., Tian, Q. & Fensholt, R. Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel. Biogeosciences 15, 319–330 (2018).
Maestre, F. T. et al. Increasing aridity reduces soil microbial diversity and abundance in global drylands. Proc. Natl Acad. Sci. USA 112, 15684–15689 (2015).
Zhang, W. et al. Ecosystem structural changes controlled by altered rainfall climatology in tropical savannas. Nat. Commun. 10, 671 (2019).
Grimm, N. B. et al. The impacts of climate change on ecosystem structure and function. Front. Ecol. Environ. 11, 474–482 (2013).
Huang, J. et al. Dryland climate change: recent progress and challenges. Rev. Geophys. 55, 719–778 (2017).
Chen, C. et al. China and India lead in greening of the world through land-use management. Nat. Sustain. 2, 122–129 (2019).
Zhu, Z. et al. Greening of the Earth and its drivers. Nat. Clim. Change 6, 791–795 (2016).
Andela, N., Liu, Y. Y., van Dijk, A. I. J. M., de Jeu, R. A. M. & McVicar, T. R. Global changes in dryland vegetation dynamics (1988–2008) assessed by satellite remote sensing: comparing a new passive microwave vegetation density record with reflective greenness data. Biogeosciences 10, 6657–6676 (2013).
Abdi, A. M., Seaquist, J., Tenenbaum, D. E., Eklundh, L. & Ardö, J. The supply and demand of net primary production in the Sahel. Environ. Res. Lett. 9, 094003 (2014).
Darkoh, M. B. K. The nature, causes and consequences of desertification in the drylands of Africa. Land Degrad. Dev. 9, 1–20 (1998).
Pricope, N. G., Husak, G., Lopez-Carr, D., Funk, C. & Michaelsen, J. The climate–population nexus in the East African Horn: Emerging degradation trends in rangeland and pastoral livelihood zones. Glob. Environ. Change 23, 1525–1541 (2013).
Huang, J., Yu, H., Guan, X., Wang, G. & Guo, R. Accelerated dryland expansion under climate change. Nat. Clim. Change 6, 166–171 (2016).
De Boeck, H. J. & Grünzweig, J. M. Drivers and mechanisms of dryland ecosystem functioning emerging in more humid biomes under climate change. Present. 2018 American Geophysical Union Fall Meeting 2018 abstr. B12B-06 (2018).
Reiss, J., Bridle, J. R., Montoya, J. M. & Woodward, G. Emerging horizons in biodiversity and ecosystem functioning research. Trends Ecol. Evol. 24, 505–514 (2009).
Jax, K. Function and “functioning” in ecology: what does it mean? Oikos 111, 641–648 (2005).
Sprugel, D. G. Disturbance, equilibrium, and environmental variability: what is ‘natural’ vegetation in a changing environment? Biol. Conserv. 58, 1–18 (1991).
Fischer, R. A. & Turner, N. C. Plant productivity in the arid and semiarid zones. Annu. Rev. Plant Physiol. 29, 277–317 (1978).
Abel, C., Horion, S., Tagesson, T., Brandt, M. & Fensholt, R. Towards improved remote sensing based monitoring of dryland ecosystem functioning using sequential linear regression slopes (SeRGS). Remote Sens. Environ. 224, 317–332 (2019).
Ratzmann, G., Gangkofner, U., Tietjen, B. & Fensholt, R. Dryland vegetation functional response to altered rainfall amounts and variability derived from satellite time series sata. Remote Sens. 8, 1026 (2016).
De Keersmaecker, W. et al. Assessment of regional vegetation response to climate anomalies: a case study for Australia using GIMMS NDVI time series between 1982 and 2006. Remote Sens. 9, 34 (2017).
De Keersmaecker, W. et al. A model quantifying global vegetation resistance and resilience to short-term climate anomalies and their relationship with vegetation cover. Glob. Ecol. Biogeogr. 24, 539–548 (2015).
Seddon, A. W. R., Macias-Fauria, M., Long, P. R., Benz, D. & Willis, K. J. Sensitivity of global terrestrial ecosystems to climate variability. Nature 531, 229–232 (2016).
Abreu, R. C. R. et al. The biodiversity cost of carbon sequestration in tropical savanna. Sci. Adv. 3, e1701284 (2017).
Brandt, M. et al. Ground- and satellite-based evidence of the biophysical mechanisms behind the greening Sahel. Glob. Change Biol. 21, 1610–1620 (2015).
Schlaepfer, D. R. et al. Climate change reduces extent of temperate drylands and intensifies drought in deep soils. Nat. Commun. 8, 14196 (2017).
Song, X.-P. et al. Global land change from 1982 to 2016. Nature 560, 639–643 (2018).
Poulter, B. et al. Contribution of semi-arid ecosystems to interannual variability of the global carbon cycle. Nature 509, 600–603 (2014).
van Dijk, A. I. J. M. et al. The Millennium Drought in southeast Australia (2001–2009): natural and human causes and implications for water resources, ecosystems, economy, and society. Water Resour. Res. 49, 1040–1057 (2013).
Venter, Z. S., Cramer, M. D. & Hawkins, H.-J. Drivers of woody plant encroachment over Africa. Nat. Commun. 9, 2272 (2018).
Stafford, W. et al. The economics of landscape restoration: benefits of controlling bush encroachment and invasive plant species in South Africa and Namibia. Ecosyst. Serv. 27, 193–202 (2017).
Acharya, B. S., Kharel, G., Zou, C. B., Wilcox, B. P. & Halihan, T. Woody plant encroachment impacts on groundwater recharge: a review. Water 10, 1466 (2018).
Bond, W. J., Stevens, N., Midgley, G. F. & Lehmann, C. E. R. The trouble with trees: afforestation plans for Africa. Trends Ecol. Evol. 34, 963–965 (2019).
Lu, X., Wang, L. & McCabe, M. F. Elevated CO2 as a driver of global dryland greening. Sci. Rep. 6, 20716 (2016).
Keenan, T. F. et al. Increase in forest water-use efficiency as atmospheric carbon dioxide concentrations rise. Nature 499, 324–327 (2013).
Schimel, D., Stephens, B. B. & Fisher, J. B. Effect of increasing CO2 on the terrestrial carbon cycle. Proc. Natl Acad. Sci. USA 112, 436–441 (2015).
United Nations Department of Economic and Social Affairs World Population Prospects 2019: Highlights (UN, 2019).
Crist, E., Mora, C. & Engelman, R. The interaction of human population, food production, and biodiversity protection. Science 356, 260–264 (2017).
Ohana-Levi, N. et al. Time series analysis of vegetation-cover response to environmental factors and residential development in a dryland region. GISci. Remote Sens. 56, 362–387 (2019).
Baumann, M. & Kuemmerle, T. The impacts of warfare and armed conflict on land systems. J. Land Use Sci. 11, 672–688 (2016).
Hickler, T. et al. Precipitation controls Sahel greening trend. Geophys. Res. Lett. 32, L21415 (2005).
Brandt, M. et al. Changes in rainfall distribution promote woody foliage production in the Sahel. Commun. Biol. 2, 133 (2019).
Marinaro, S., Grau, H. R., Ignacio Gasparri, N., Kuemmerle, T. & Baumann, M. Differences in production, carbon stocks and biodiversity outcomes of land tenure regimes in the Argentine Dry Chaco. Environ. Res. Lett. 12, 045003 (2017).
Gasparri, N. I. & Grau, H. R. Deforestation and fragmentation of Chaco dry forest in NW Argentina (1972–2007). For. Ecol. Manage. 258, 913–921 (2009).
Ordway, E. M., Asner, G. P. & Lambin, E. F. Deforestation risk due to commodity crop expansion in sub-Saharan Africa. Environ. Res. Lett. 12, 44015 (2017).
Jew, E. K. K., Dougill, A. J. & Sallu, S. M. Tobacco cultivation as a driver of land use change and degradation in the Miombo woodlands of south-west Tanzania. Land Degrad. Dev. 28, 2636–2645 (2017).
Diffenbaugh, N. S. & Burke, M. Global warming has increased global economic inequality. Proc. Natl Acad. Sci. USA 116, 9808–9813 (2019).
IPCC Climate Change 2014: Impacts, Adaptation and Vulnerability (eds Field, C. B. et al.) (Cambridge Univ. Press, 2014).
Jain, H. K. Green Revolution: History, Impact and Future (Studium Press LLC, 2010).
Hodgson, D., McDonald, J. L. & Hosken, D. J. What do you mean, ‘resilient’? Trends Ecol. Evol. 30, 503–506 (2015).
Herrmann, S. M., Anyamba, A. & Tucker, C. J. Recent trends in vegetation dynamics in the African Sahel and their relationship to climate. Glob. Environ. Change 15, 394–404 (2005).
Nemani, R. R. et al. Climate-driven increases in global terrestrial net orimary production from 1982 to 1999. Science 300, 1560–1563 (2003).
Land Cover CCI: Product User Guide: Version 2.0 (ESA, 2017).
Zomer, A. & Trabucco, R. Global aridity index and potential evapotranspiration (ET0) climate database v2. Figshare https://doi.org/10.6084/m9.figshare.7504448.v3 (2019).
Vermote, E., Wolfe, R., NASA GSFC and MODAPS SIPS-NASA MOD09GQ MODIS and the Terra Surface Reflectance Daily L2G Global 250m SIN Grid V006 (NASA EOSDIS LP DAAC, accessed February 2020); http://doi.org/10.5067/MODIS/MOD09GQ.006
Vermote, E. MOD09A1 MODIS Surface Reflectance 8-Day L3 Global 500m SIN Grid V006 (NASA EOSDIS Land Processes DAAC, 2015).
Fensholt, R. & Proud, S. R. Evaluation of Earth Observation based global long term vegetation trends—comparing GIMMS and MODIS global NDVI time series. Remote Sens. Environ. 119, 131–147 (2012).
Tian, F. et al. Evaluating temporal consistency of long-term global NDVI datasets for trend analysis. Remote Sens. Environ. 163, 326–340 (2015).
Anyamba, A. & Tucker, C. J. Analysis of Sahelian vegetation dynamics using NOAA-AVHRR NDVI data from 1981–2003. J. Arid. Environ. 63, 596–614 (2005).
Olsen, J. L., Miehe, S., Ceccato, P. & Fensholt, R. Does EO NDVI seasonal metrics capture variations in species composition and biomass due to grazing in semi-arid grassland savannas? Biogeosciences 12, 4407–4419 (2015).
Tagesson, T. et al. Spatiotemporal variability in carbon exchange fluxes across the Sahel. Agric. For. Meteorol. 226–227, 108–118 (2016).
Multi-Sensor Vegetation Index and Phenology Earth Science Data Records Version 4.0 (Vegetation Index and Phenology Lab, The University of Arizona, accessed February 2020); https://lpdaac.usgs.gov/products/vipphen_ndviv004/
Zwart, S. J., Mishra, B. & Dembélé, M. Satellite rainfall for food security on the African continent: performance and accuracy of seven rainfall products between 2001 and 2016. In Remote Sensing and Hydrology Symposium (2018).
Beck, H. E. et al. Global-scale evaluation of 22 precipitation datasets using gauge observations and hydrological modeling. Hydrol. Earth Syst. Sci. 21, 6201–6217 (2017).
Burrell, A. L., Evans, J. P. & Liu, Y. The impact of dataset selection on land degradation assessment. ISPRS J. Photogramm. Remote Sens. 146, 22–37 (2018).
Beck, H. E. et al. MSWEP: 3-hourly 0.25° global gridded precipitation (1979–2015) by merging gauge, satellite, and reanalysis data. Hydrol. Earth Syst. Sci. 21, 589–615 (2017).
Copernicus Climate Change Service (C3S) (2019): C3S ERA5-Land reanalysis (Copernicus Climate Change Service, accessed February 2020); https://cds.climate.copernicus.eu/cdsapp#!/home
Giglio, L., Boschetti, L., Roy, D. P., Humber, M. L. & Justice, C. O. The Collection 6 MODIS burned area mapping algorithm and product. Remote Sens. Environ. 217, 72–85 (2018).
Center for International Earth Science Information Network - CIESIN - Columbia University Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11 (NASA Socioeconomic Data and Applications Center (SEDAC), accessed February 2020); https://doi.org/10.7927/H49C6VHW
Gross Domestic Product (GDP) (current US$) as of 2015 (World Bank, accessed July 2020); https://data.worldbank.org/indicator/NY.GDP.MKTP.CD
Zuur, A., Ieno, E. N. & Smith, G. M. Analyzing Ecological Data (Springer-Verlag, 2007).
Venter, O. et al. Last of the Wild Project, Version 3 (LWP-3): 2009 Human Footprint, 2018 Release (NASA Socioeconomic Data and Applications Center (SEDAC), accessed February 2020); https://doi.org/10.7927/H46T0JQ4
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).
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
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
Scientific Reports (2021)
Environmental Chemistry Letters (2021)