Lilian Vallet

So proud to be part of this amazing team. A lot of projects going on and even more coming in the future, stay tuned! 🌳🔥🛰️

Vous souhaitez en apprendre plus sur la vulnérabilité des forêts et zones agricoles face aux incendies ? 🔥🌳
Mais, vous n'avez pas le temps de lire les 250 pages que compose ma thèse ?
Ça tombe bien, l'académie d'Agriculture vient d'en faire une synthèse 👇
Merci à Yves Birot pour son analyse

Regardons la communauté des followers de @cnrsecologie.bsky.social , qui étudie l'environnement
On distingue 5 communautés

Soil smoldering in temperate forests: a neglected contributor to fire carbon emissions revealed by atmospheric mixing ratios Abstract. Fire is regarded as an essential climate variable, emitting greenhouse gases in the combustion process. Current global assessments of fire emissions traditionally rely on coarse remotely sen...

link to the study : bg.copernicus.org/articles/22/...
@ird-fr.bsky.social @fireurisk.eu @cnrs.bsky.social @cnrsecologie.bsky.social @umontpellier.bsky.social @lsce-ipsl.bsky.social @copernicusecmwf.bsky.social @ecmwf.bsky.social @icos-ri.eu

We need to adapt global models to regional conditions to ensure accurate estimation of the processes that will be transformed by future climate conditions.

Climate change seems bound to push fires further north, towards temperate forests.
This process should increase the C emissions balance to significant levels (here : 2% of the national balance, 30% of annual sequestration by forests).

As a result, the total carbon footprint for the 2022 fire season in France amounts to 7.95 million tonnes of CO2 equivalent.
Global models, which did not take into account the underground parts of temperate forests, predicted a balance 2 times lower (4.18 MtCo2e).

It is estimated that 1.15 million tonnes of CO were emitted by fires in 2022.

For this molecule, underground compartments are becoming the dominant source!

Our model estimates that 6.15 million tonnes of CO2 were emitted by the fires.
In terms of this molecule, soil and aerial parts account for an equal share.
The Landes region dominates this assessment (large surface area burned, high concentration of C in the soil).

In total, it is estimated that 4.5 million tonnes (dry mass) will be combusted in 2022, all compartments combined.

Subterranean compartments, in particular soil and lignite, play an important role in this balance.

We have thus built a new fire emission model, with aerial compartments (trees, shrubs, herbaceous plants, litter) and underground compartments (soil, peat bogs, lignite).
This 10m-resolution model is calibrated with data from the Atmospheric towers.

We have observed that this type of combustion can be favored by various factors: a high carbon density in the soil, the presence of peat bogs or lignite, low fire propagation speed, high fire intensity, etc.

Smoldering combustion can occur in various ecosystem compartments (e.g. wood), but such high values are generally associated with combustion in the subterranean soil layers. This corroborates evidence of fumaroles and deep combustion (Landes).

When a large quantity of carbon monoxide (CO) is released relative to dioxide (CO2), this is considered to be smoldering combustion (absence of O).
Here, we sometimes observe MCEs of 0.75, i.e. a quantity of CO emitted for only 3 of CO2!

The quantities of CO and CO2 vary from site to site:
In the Mediterranean (OHP), the signal corresponds to normal surface combustion (low CO).
In the Landes (BIS) and Brittany (ROC), very high CO values are obtained at times

*MCE=CO2/(CO2+CO)

We had to retrace the path of the molecules from the fire, in the atmosphere and thus obtain the points of intersection with the atmospheric towers (including @icos-ri.eu towers)

This work was carried out by colleagues from @universitereims.bsky.social (C.Abdallah, T. Lauvaux & L.Joly)🙏

In 🔵⚪🔴, we have a nationwide network of atmospheric towers, which measure molecule quantities in real time.
We have taken advantage of the proximity of certain towers (OHP, ROC, BIS) to wildfires to analyze changes in CO2 and CO

How does this redistribution to the North affect the carbon balance of fires?
What role does soil combustion play in these ecosystems?
Do global models and inventories correctly estimate these emissions?

While fires affect ecosystems with low biomass in the Mediterranean (garrigue, low forest), this redistribution of occurrence to temperate forests increases the amount of biomass affected 🌳

Total: 2.55 million tonnes of vegetation affected in 2022

In 2022, the area burnt in France amounts to 42,500 hectares 🔥
Very large fires in the Landes (26,800 ha vs. 494 ha/year over 2006-2021)
Numerous fires in temperate forests (7,800 ha vs. 216 ha/year)
Surface burned within norms in the Mediterranean (7,900 ha)

🚨NEW SCIENTIFIC STUDY🚨

8 million tonnes of CO2
~ 2% of french greenhouse gas emissions 🔵⚪🔴
~ 30% of the national sequestration capacity of the forest🌳

That's the carbon emissions from fires in 2022! 🔥

⚠️Predominant effect of soil combustion

🧵👇

The scars of the fires encircling Los Angeles as seen by Sentinel-2 (SWIR) on January 12 🛰🔥