Satellite-based mapping of canopy fuels at the pan-European scale

Canopy base height (CBH) and canopy bulk density (CBD) are forest canopy fuel parametersthat are key for modeling the behavior of crown wildfires. In this work, we map them at a pan-European scale for the year 2020, producing a new dataset consisting of two raster layerscontaining both variables at an approximate resolution of 100 m. Spatial data from Earthobservation missions and derived down-stream products were retrieved and processed usingartificial intelligence to first estimate a map of aboveground biomass (AGB). Allometric modelswere then used to estimate the spatial distribution of CBH using the canopy height values asexplanatory variables and CBD using AGB values. Ad-hoc allometric models were defined forthis study. Data provided by FIRE-RES project partners and acquired through field inventorieswas used for validating the final products using an independent dataset of 804 ground-truthsample plots. The CBH and CBD raster maps have, respectively, the following accuracy regard-ing specific metrics reported from the modeling procedures: (i) coefficient of correlation (R) of0.445 and 0.330 (p-value < 0.001); (ii) root mean square of error (RMSE) of 3.9 m and 0.099kg m−3; and (iii) a mean absolute percentage error (MAPE) of 61% and 76%. Regarding CBD, theaccuracy metrics improved in closed canopies (canopy cover > 80%) to R = 0.457, RMSE = 0.085,and MAPE = 59%. In short, we believe that the degree of accuracy is reasonable in the resultingmaps, producing CBH and CBD datasets at the pan-European scale to support fire mitigationand crown fire simulations