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Economic efficiency and targeting of the African Great Green Wall

Abstract

Land degradation in the Sahel threatens livelihoods and food security. The Great Green Wall programme is a colossal initiative to restore 100 million hectares of degraded ecosystems across 11 countries in the region, which started in 2007 to also promote sustainable development and climate change mitigation. We evaluated the economic costs and benefits of future land restoration projects under this programme. We applied different scenarios that account for both market-priced and non-market benefits from restored ecosystems and consider the heterogeneity of local decision-making contexts in terms of investment planning horizons, discount rates, and the time needed for the restored ecosystems to start yielding their benefits in full. The results show that every US dollar invested into land restoration yields on average US$1.2 under the base scenario, ranging from US$1.1 to US$4.4 across the scenarios. At most, ten years are needed for land restoration activities to break even from the social perspective, accounting for both market-priced and non-market ecosystem benefits. To fund all proposed land restoration activities, an investment of US$44 billion is needed under the base scenario (US$18–70 billion across scenarios). Violent conflicts in the Sahel are estimated to reduce the accessibility to these degraded ecosystems from 27.9 million hectares to 14.1 million hectares. The study highlights activities and locations where land restoration is both economically attractive and ecologically sustainable, even after accounting for lower survival rates of planted trees and grasses, persistence of land degradation drivers and the growing number of violent conflicts hindering land restoration in the Sahel. This information can help improve the targeting of future land restoration activities in the region.

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Fig. 1: Trends in the economic values of land ecosystem services in the Sahel.
Fig. 2: The costs of land degradation and benefits from land improvement (2001–2018).
Fig. 3: Benefit/cost ratios of land restoration under S1.

Data availability

The data generated by the current study are available in the paper and Supplementary Materials. The citations to the external data sources used by the study are given in the references and Supplementary Materials. All correspondence and requests for materials should be addressed to the corresponding author.

Code availability

The codes used in the analysis are available at Open Science framework (https://osf.io/7kaer/).

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Acknowledgements

The collaboration and support of the Pan-African and National agencies of the Great Green Wall are acknowledged. We also thank J. von Braun for comments and suggestions on the earlier versions of the paper. This study was conducted under Action Against Desertification, an initiative of the Organisation of African, Caribbean and Pacific States (OACPS), implemented by the United Nations’ Food and Agriculture Organization and funded by the European Union (GCP/INT/157/EC).

Author information

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Contributions

A.Mirzabaev conceived and designed the analysis, planned and supervised the work, collected the data, implemented the analysis, interpreted the data and wrote the manuscript. M.S. planned and supervised the work and contributed to data interpretation and writing of the manuscript. F.M. collected the data, contributed to data analysis and produced the maps. A.S. collected the data and contributed to data interpretation and preparation of Supplementary Materials. A.Martucci contributed to data analysis and produced the maps.

Corresponding author

Correspondence to A. Mirzabaev.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Sustainability thanks Jacob Hochard and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Median values of ecosystem services in the Sahel region (USD per hectare).

Source: estimated by the authors based on the references indicated in Supplementary Material 8.

Extended Data Fig. 2 Assumptions for land restoration activities.

Note: The assumptions imply that restored forests, woodlands, shrublands and wetlands do not start yielding their all ecosystem benefits immediately but reach their full potential gradually.

Extended Data Fig. 3 Country-specific benefit cost ratios of restoring degraded biomes across the scenarios.

Note: The ranges signify minimum and maximum returns (in USD) for each USD invested for restoration across the scenarios.

Extended Data Fig. 4 Regional benefit-cost ratios of restoring degraded biomes under each scenario.

Note: S-Scenario. The numbers signify the average returns (in USD) at the regional level for each USD invested for restoring each biome.

Extended Data Fig. 5 Locations suitable for land restoration after accounting for conflicts.

Note: The underlying analysis assumes that land restoration is not possible in areas which are within 50 km of violent conflict spots. The map shows the findings for the base scenario 1. Source: the authors.

Extended Data Fig. 6 Locations of violent conflicts across the Sahel region.

Note: The map shows the locations of incidences of violent conflicts and one-sided violence since 2015 exceeding 25 fatalities a year. Source: produced by the authors based on Uppsala Conflict Data Program (UCDP) database.

Supplementary information

Supplementary Information

Supplementary Materials 1–8.

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Mirzabaev, A., Sacande, M., Motlagh, F. et al. Economic efficiency and targeting of the African Great Green Wall. Nat Sustain 5, 17–25 (2022). https://doi.org/10.1038/s41893-021-00801-8

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