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Global spatial assessment of potential for new peri-urban forests to combat climate change

Nature Cities volume 1, pages 286–294 (2024)Cite this article

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Abstract

Forests hold and remove vast quantities of carbon dioxide from the atmosphere. Given the challenges of reducing emissions quickly enough and the stakes involved, planting new trees is therefore crucial in the broader battle against climate change. Accordingly, the proposal from the G20 summit of November 2021, to fight the climate crisis by planting 1 trillion trees by 2030, has been accepted, elevating tree restoration as an emissions-reduction strategy. At the same time, increasing urbanization has rendered more and more forested areas to the periphery of cities. Here we show that, globally, between 141 and 322 Mha are potentially available for tree restoration in such peri-urban areas. New forests around cities could provide crucial ecosystem services, improving air quality, mitigating temperatures, reducing heat islands and removing greenhouse gases as well as other pollution from the atmosphere. We constructed a 500-m-resolution global map of the peri-urban areas suitable for tree restoration. We found that these areas may host between 241 and 106 billion trees, depending on different land-availability scenarios, and between 101 and 34 billion trees when excluding areas that currently serve as croplands. Almost 80% of such trees could be hosted in just 20 countries. Although forest restoration activities such as tree planting cannot replace reducing carbon emissions, incrementing peri-urban forests can play a crucial role in the fight against climate change. Our results and the maps we constructed may help decision-makers to come to more informed decisions about where to focus reforestation efforts.

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Fig. 1: Infographic summarizing the data used and the methods implemented in this study.
Fig. 2: Land cover of peri-urban areas and available areas for forest restoration activities under the three scenarios.
Fig. 3
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Data availability

To ensure the full reproducibility and transparency of our research, we provide all of the data used in our analysis at https://code.earthengine.google.com/?accept_repo=users/sfrancini/urban. Raw data are available in the Google Earth Engine catalog at https://developers.google.com/earth-engine/datasets. The GAIA dataset is available at https://developers.google.com/earth-engine/datasets/catalog/Tsinghua_FROM-GLC_GAIA_v10. The PDB is available at https://developers.google.com/earth-engine/datasets/catalog/OpenLandMap_PNV_PNV_BIOME-TYPE_BIOME00K_C_v01. The WorldCover map is available at https://developers.google.com/earth-engine/datasets/catalog/ESA_WorldCover_v100. The JAXA forest mask is available at https://developers.google.com/earth-engine/datasets/catalog/JAXA_ALOS_PALSAR_YEARLY_FNF.

Code availability

The Google Earth Engine codes used to obtain final and intermediate products can be accessed at the Google Earth Engine repository at https://code.earthengine.google.com/?accept_repo=users/sfrancini/urban. To access the repository a Google Earth Engine account is needed. If readers need support in executing the codes or in downloading final and intermediate products please ask for support to saverio.francini@unifi.it

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Acknowledgements

This study was supported by the following projects: PNRR, funded by the Italian Ministry of University and Research, Missione 4 Componente 2, ‘Dalla ricerca all’impresa’, Investimento 1.4, Project CN00000033; MULTIFOR ‘Multi-scale observations to predict Forest response to pollution and climate change’ PRIN 2020 Research Project of National Relevance funded by the Italian Ministry of University and Research (prot. 2020E52THS); SUPERB ‘Systemic solutions for upscaling of urgent ecosystem restoration for forest related biodiversity and ecosystem services’ H2020 project funded by the European Commission, number 101036849 call LC-GD-7-1-2020; EFINET ‘European Forest Information Network’ funded by the European Forest Institute, Network Fund G-01-2021; and FORWARDS: the forestward observatory to secure resilience of european forests (Project 101084481). We thank N. Gorelick, one of the founders of Google Earth Engine, for the continuous support he has given us.

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Authors and Affiliations

  1. Fondazione per il Futuro delle Città, Florence, Italy

    Saverio Francini, Gherardo Chirici, Leonardo Chiesi, Guido Caldarelli & Stefano Mancuso

  2. Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali, Università degli Studi di Firenze, Florence, Italy

    Saverio Francini & Gherardo Chirici

  3. Dipartimento di Scienze Politiche e Sociali, Università degli Studi di Firenze, Florence, Italy

    Leonardo Chiesi & Paolo Costa

  4. DSMN, Ca’ Foscari University of Venice, Venice, Italy

    Guido Caldarelli

  5. CNR-ISC, Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy

    Guido Caldarelli

  6. London Institute for Mathematical Sciences, Royal Institution, London, UK

    Guido Caldarelli

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Contributions

S.M., S.F., and G. Chirici conceived the idea. S.F., G. Chirici and S.M. designed the methodology. S.F. performed the analysis and wrote the Google Earth Engine codes. S.F. wrote the paper with contributions from G. Chirici, L.C., P.C., G. Caldarelli and S.M.

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Correspondence to Saverio Francini.

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Nature Cities thanks Paloma Carinanos, Cynnamon Dobbs, Sophia Ratcliffe and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1 and 2.

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Supplementary Data 1

Accuracy assessment of predicted areas available for forest restoration activities.

Supplementary Data 2

Comparison between restoration areas committed by countries within the Bonn Challenge and the available peri-urban areas we identified under the three scenarios.

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Francini, S., Chirici, G., Chiesi, L. et al. Global spatial assessment of potential for new peri-urban forests to combat climate change. Nat Cities 1, 286–294 (2024). https://doi.org/10.1038/s44284-024-00049-1

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