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Proc Natl Acad Sci U S A. 2016 Oct 11;113(41):11471-11476. Epub 2016 Sep 26.

Green and blue water demand from large-scale land acquisitions in Africa.

Author information

1
Department of Physical Geography and Ecosystem Science, Lund University, Lund SE-223 62, Sweden; emma.johansson@nateko.lu.se.
2
International Centre for Water Resources and Global Change (UNESCO), Federal Institute of Hydrology, 56002 Koblenz, Germany; Institut Méditerranéen de Biodiversité et d'Ecologie Marine et Continentale, Technopôle Arbois-Méditerranée, F-13545 Aix-en-Provence cedex 04, France.
3
Department of Physical Geography and Ecosystem Science, Lund University, Lund SE-223 62, Sweden.
4
Centre for Sustainability Studies, Lund University, Lund SE-221 00, Sweden.

Abstract

In the last decade, more than 22 million ha of land have been contracted to large-scale land acquisitions in Africa, leading to increased pressures, competition, and conflicts over freshwater resources. Currently, 3% of contracted land is in production, for which we model site-specific water demands to indicate where freshwater appropriation might pose high socioenvironmental challenges. We use the dynamic global vegetation model Lund-Potsdam-Jena managed Land to simulate green (precipitation stored in soils and consumed by plants through evapotranspiration) and blue (extracted from rivers, lakes, aquifers, and dams) water demand and crop yields for seven irrigation scenarios, and compare these data with two baseline scenarios of staple crops representing previous water demand. We find that most land acquisitions are planted with crops that demand large volumes of water (>9,000 m3⋅ha-1) like sugarcane, jatropha, and eucalyptus, and that staple crops have lower water requirements (<7,000 m3⋅ha-1). Blue water demand varies with irrigation system, crop choice, and climate. Even if the most efficient irrigation systems were implemented, 18% of the land acquisitions, totaling 91,000 ha, would still require more than 50% of water from blue water sources. These hotspots indicate areas at risk for transgressing regional constraints for freshwater use as a result of overconsumption of blue water, where socioenvironmental systems might face increased conflicts and tensions over water resources.

KEYWORDS:

LPJmL; irrigation; land grabbing; water footprints; water scarcity

PMID:
27671634
PMCID:
PMC5068327
DOI:
10.1073/pnas.1524741113
[Indexed for MEDLINE]
Free PMC Article

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