Preprints
https://doi.org/10.5194/egusphere-2024-710
https://doi.org/10.5194/egusphere-2024-710
21 Mar 2024
 | 21 Mar 2024

Global and Regional Hydrological Impacts of Global Forest Expansion

James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin

Abstract. Large-scale reforestation, afforestation, and forest restoration schemes have gained global support as climate change mitigation strategies due to their significant carbon dioxide removal (CDR) potential. However, there has been limited research into the unintended consequences of forestation from a biophysical perspective. In the Community Earth System Model version 2 (CESM2), we apply a global forestation scenario, within a Paris Agreement-compatible warming scenario to investigate the land surface and hydroclimate response. Compared to a control scenario where land use is fixed to present-day levels, the forestation scenario is up to 2 °C cooler at low latitudes by 2100, driven by a 10 % increase in evaporative cooling in forested areas. However, afforested areas where grassland or shrubland are replaced lead to a doubling of plant water demand in some tropical regions, causing significant decreases in soil moisture (~5 % globally, 5–10 % regionally) and water availability (~10 % globally, 10–15 % regionally) in regions with increased forest cover. While there are some increases in low cloud and seasonal precipitation over the expanded tropical forests, with enhanced negative cloud radiative forcing, the impacts on large-scale precipitation and atmospheric circulation are limited. This contrasts with the precipitation response to simulated large-scale deforestation found in previous studies. The forestation scenario demonstrates local cooling benefits without major disruption to global hydrodynamics beyond those already projected to result from climate change, in addition to the cooling associated with CDR. However, the water demands of extensive forestation, especially afforestation, have implications for its viability given uncertainty in future precipitation changes.

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Journal article(s) based on this preprint

03 Sep 2024
| Highlight paper
Global and regional hydrological impacts of global forest expansion
James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin
Biogeosciences, 21, 3883–3902, https://doi.org/10.5194/bg-21-3883-2024,https://doi.org/10.5194/bg-21-3883-2024, 2024
Short summary Co-editor-in-chief
James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-710', Anonymous Referee #1, 27 Apr 2024
    • AC1: 'Reply on RC1', James A. King, 30 May 2024
  • RC2: 'Comment on egusphere-2024-710', Anonymous Referee #2, 03 May 2024
    • AC2: 'Reply on RC2', James A. King, 30 May 2024

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-710', Anonymous Referee #1, 27 Apr 2024
    • AC1: 'Reply on RC1', James A. King, 30 May 2024
  • RC2: 'Comment on egusphere-2024-710', Anonymous Referee #2, 03 May 2024
    • AC2: 'Reply on RC2', James A. King, 30 May 2024

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Reconsider after major revisions (05 Jun 2024) by Anja Rammig
AR by James A. King on behalf of the Authors (05 Jun 2024)  Author's response   Author's tracked changes   Manuscript 
ED: Reconsider after major revisions (19 Jun 2024) by Anja Rammig
ED: Referee Nomination & Report Request started (19 Jun 2024) by Anja Rammig
RR by Anonymous Referee #2 (02 Jul 2024)
ED: Publish as is (05 Jul 2024) by Anja Rammig
AR by James A. King on behalf of the Authors (11 Jul 2024)

Journal article(s) based on this preprint

03 Sep 2024
| Highlight paper
Global and regional hydrological impacts of global forest expansion
James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin
Biogeosciences, 21, 3883–3902, https://doi.org/10.5194/bg-21-3883-2024,https://doi.org/10.5194/bg-21-3883-2024, 2024
Short summary Co-editor-in-chief
James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin

Data sets

CESM2 land use data for study on hydrological impacts of large-scale forest expansion James A. King https://doi.org/10.5281/zenodo.10782834

CESM2 land output data for study on hydrological impacts of large-scale forest expansion James A. King https://doi.org/10.5281/zenodo.10797041

CESM2 atmosphere output data for study on hydrological impacts of large-scale forest expansion James A. King https://doi.org/10.5281/zenodo.10797083

CESM2 atmosphere output data for study on hydrological impacts of large-scale forest expansion James A. King https://doi.org/10.5281/zenodo.10797087

CESM2 atmosphere output data for study on hydrological impacts of large-scale forest expansion James A. King https://doi.org/10.5281/zenodo.10797092

James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Large-scale afforestation and reforestation are today seen as an important global climate mitigation strategy. The study investigates the climate feedbacks from afforestation and reforestation with a focus on hydrodynamic processes. The study shows that feedbacks on precipitation and local temperature are more complex and that is important to look beyond carbon cycle feedbacks when it comes to the implementation of climate mitigation strategies.
Short summary
Tackling climate change by adding, restoring, or enhancing forests is gaining global support. However, it’s important to investigate the broader implications of this. We used a computer model of the Earth to investigate a future where tree cover expanded as much as possible. We found that some tropical areas were cooler because of trees pumping water into the atmosphere, but this also led to soil and rivers drying. This is important because it might be harder to maintain the forests as a result.