Preprints
https://doi.org/10.5194/egusphere-2023-529
https://doi.org/10.5194/egusphere-2023-529
05 Apr 2023
 | 05 Apr 2023

High resolution data reveal a surge of biomass loss from temperate and Atlantic pine forests, seizing the 2022 fire season distinctiveness in France

Lilian Vallet, Martin Schwartz, Philippe Ciais, Dave van Wees, Aurelien de Truchis, and Florent Mouillot

Abstract. The frequency and intensity of summer droughts and heat waves in Western Europe have been increasing, raising concerns about the emergence of fire hazard in less fire prone areas. This exposure of old-growth forests hosting unadapted tree species may cause disproportionately large biomass losses compared to those observed in frequently burned Mediterranean ecosystems. Therefore, analyzing fire seasons from the perspective of exposed burned areas alone is insufficient, we must also consider impacts on biomass loss. In this study, we focus on the exceptional 2022 summer fire season in France and use very high-resolution (10 m) satellite data to calculate the burned area, tree height at the national level, and the subsequent ecological impact based on biomass loss during fires. Our high resolution semi-automated detection estimated 42,520 ha of burned area, compared to the 66,393 ha estimated by the European automated remote sensing detection system (EFFIS), including 48,330 ha actually occurring in forests. We show that Mediterranean forests had a lower biomass loss than in previous years, whereas there was a drastic increase in burned area and biomass loss over the Atlantic pine forests and temperate forests. High biomass losses in the Atlantic pine forests were driven by the large burned area (28,600 ha in 2022 vs. 494 ha yr−1 in 2006–2021 period) but mitigated by a low exposed tree biomass mostly located on intensive management areas. Conversely, biomass loss in temperate forests was abnormally high due to both a 15-fold increase in burned area compared to previous years (3,300 ha in 2022 vs. 216 ha in the 2006–2021 period) and a high tree biomass of the forests which burned. Overall, the biomass loss (i.e. wood biomass dry weight) was 0.25 Mt in Mediterranean forests and shrublands, 1.74 Mt in the Atlantic pine forest, and 0.57 Mt in temperate forests, amounting to a total loss of 2.553 Mt, equivalent to a 17 % increase of the average natural mortality of all French forests, as reported by the national inventory. A comparison of biomass loss between our estimates and global biomass/burned areas data indicates that higher resolution improves the identification of small fire patches, reduces the commission errors with a more accurate delineation of the perimeter of each fire, and increases the biomass affected. This study paves the way for the development of low-latency, high-accuracy assessment of biomass losses and fire patch contours to deliver a more informative impact-based characterization of each fire year.

Journal article(s) based on this preprint

20 Sep 2023
| Highlight paper
High-resolution data reveal a surge of biomass loss from temperate and Atlantic pine forests, contextualizing the 2022 fire season distinctiveness in France
Lilian Vallet, Martin Schwartz, Philippe Ciais, Dave van Wees, Aurelien de Truchis, and Florent Mouillot
Biogeosciences, 20, 3803–3825, https://doi.org/10.5194/bg-20-3803-2023,https://doi.org/10.5194/bg-20-3803-2023, 2023
Short summary Co-editor-in-chief

Lilian Vallet et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-529', Anonymous Referee #1, 02 Jun 2023
    • AC1: 'Reply on RC1', Lilian Vallet, 21 Jun 2023
  • RC2: 'Comment on egusphere-2023-529', Anonymous Referee #2, 06 Jun 2023
    • AC2: 'Reply on RC2', Lilian Vallet, 21 Jun 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-529', Anonymous Referee #1, 02 Jun 2023
    • AC1: 'Reply on RC1', Lilian Vallet, 21 Jun 2023
  • RC2: 'Comment on egusphere-2023-529', Anonymous Referee #2, 06 Jun 2023
    • AC2: 'Reply on RC2', Lilian Vallet, 21 Jun 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Publish subject to minor revisions (review by editor) (25 Jun 2023) by David McLagan
AR by Lilian Vallet on behalf of the Authors (26 Jun 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (29 Jun 2023) by David McLagan
AR by Lilian Vallet on behalf of the Authors (18 Jul 2023)

Journal article(s) based on this preprint

20 Sep 2023
| Highlight paper
High-resolution data reveal a surge of biomass loss from temperate and Atlantic pine forests, contextualizing the 2022 fire season distinctiveness in France
Lilian Vallet, Martin Schwartz, Philippe Ciais, Dave van Wees, Aurelien de Truchis, and Florent Mouillot
Biogeosciences, 20, 3803–3825, https://doi.org/10.5194/bg-20-3803-2023,https://doi.org/10.5194/bg-20-3803-2023, 2023
Short summary Co-editor-in-chief

Lilian Vallet et al.

Data sets

Aboveground biomass loss (AGB-L) by fire over 2020-2022 period Vallet, Lilian; Schwartz, Martin; Ciais, Philippe; van Wees, Dave; de Truchis, Aurélien; Mouillot, Florent https://doi.org/10.15148/3db37fdf-46b1-4e7a-bd86-ca4fb93307e1

Lilian Vallet et al.

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Latest update: 20 Sep 2023
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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.

The study covers a relevant contemporary topic (wildfire) and focusses on the recent major European summer of wildfires. The authors demonstrate that the assessment of burned area alone is not enough to fully characterize the impact of fires. Novel methods to assess burned area and above ground biomass losses are described to provide a more informative impact-based characterization of fires.
Short summary
This study analyzes the ecological impact of the 2022 summer fire season in France by using high-resolution satellite data. The total biomass loss was 2.553 Mt, equivalent to a 17 % increase of the average natural mortality of all French forests. While Mediterranean forests had a lower biomass loss, there was a drastic increase in burned area and biomass loss over the Atlantic pine forests and temperate forests. This result revisits the 2022 fire season distinctiveness.