Preprints
https://doi.org/10.5194/egusphere-2025-1800
https://doi.org/10.5194/egusphere-2025-1800
05 May 2025
 | 05 May 2025

Shifts in global atmospheric oxidant chemistry from land cover change

Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer

Abstract. Human activities have profoundly altered natural vegetation, primarily by converting pristine land for agriculture and grazing. Land cover change (LCC) influences the Earth system through modifications of surface albedo, roughness length, evapotranspiration, and atmospheric composition. This work investigates how LCC-driven changes in BVOC fluxes, anthropogenic surface emissions, natural soil NO emissions, and O3 deposition fluxes affect atmospheric chemistry. The chemistry–climate model EMAC was used to compare: (1) present-day land cover, which includes areas deforested for crops and grazing, with the potential natural vegetation (PNV) cover simulated by the model, and (2) an extreme reforestation scenario where grazing land is restored to natural vegetation. Our results show that the expansion of agricultural land reduces global BVOC emissions, leading to lower annual average surface OH concentrations (−5.7 %) and CO mixing ratios (−6.2 %), despite increased CO from agricultural burning. Meanwhile, NOx mixing ratios increase (+7.8 %) due to enhanced anthropogenic and natural soil sources. While regional ozone responses vary, global ozone production sensitivity shifts from a NOx- to a VOC-sensitive regime. These changes influence radiative forcing: reductions in tropospheric O3 and CH4 lifetimes exert a combined net cooling of −60 mW m−2, partially offset by warming from reduced BVOC-driven SOA formation. Reforestation of grazing areas reverses these trends to some extent, though with a weaker response.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Journal article(s) based on this preprint

05 Sep 2025
Changes in global atmospheric oxidant chemistry from land cover conversion
Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer
Atmos. Chem. Phys., 25, 9885–9904, https://doi.org/10.5194/acp-25-9885-2025,https://doi.org/10.5194/acp-25-9885-2025, 2025
Short summary
Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1800', Anonymous Referee #1, 01 Jun 2025
  • RC2: 'Comment on egusphere-2025-1800', Anonymous Referee #2, 06 Jun 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1800', Anonymous Referee #1, 01 Jun 2025
  • RC2: 'Comment on egusphere-2025-1800', Anonymous Referee #2, 06 Jun 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Ryan Vella on behalf of the Authors (18 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (27 Jun 2025) by Radovan Krejci
AR by Ryan Vella on behalf of the Authors (29 Jun 2025)

Journal article(s) based on this preprint

05 Sep 2025
Changes in global atmospheric oxidant chemistry from land cover conversion
Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer
Atmos. Chem. Phys., 25, 9885–9904, https://doi.org/10.5194/acp-25-9885-2025,https://doi.org/10.5194/acp-25-9885-2025, 2025
Short summary
Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer
Ryan Vella, Sergey Gromov, Clara M. Nussbaumer, Laura Stecher, Matthias Kohl, Samuel Ruhl, Holger Tost, Jos Lelieveld, and Andrea Pozzer

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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.

Short summary
We evaluated how replacing forests with farmland and grazing areas affects atmospheric composition. Using a global climate-chemistry model, we found that deforestation reduces BVOCs, increases farming pollutants, and shifts ozone chemistry. These changes lead to a small cooling effect on the climate. Restoring natural vegetation could reverse some of these effects.
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