The model BLUE (Bookeeping of Land Use Emissions)

BLUE (Bookkeeping of Land Use Emissions) is a carbon model for quantifying CO₂ fluxes from human land use and land-use changes (LULUC). Every year, BLUE contributes simulations to estimate land-use change emissions for the Global Carbon Budget. BLUE is a spatially explicit semi-empirical model: it combines spatially explicit datasets on land-use changes (such as deforestation, reforestation) or land management (such as wood harvest) with empirical data on soil and vegetation carbon densities to estimate the resulting carbon fluxes. BLUE is characterized by its ability to account for successive LULUC events and their interactions, model time-delayed fluxes resulting from past land-use changes, and track fluxes over time, which makes it possible to track the contribution of past LULUC events on current carbon fluxes. BLUE's flexible design also allows it to be used in conjunction with various historical land-use datasets, including LUH2 and HILDA+. A detailed description of BLUE is available in Hansis et al. (2015).

Our chair is continuously developing BLUE to expand its range of application. To better reflect the effects of changing environmental conditions, carbon densities from dynamic global vegetation models (DGVMs) have recently been integrated into BLUE (Dorgeist et al., 2024). Thanks to this enhancement, BLUE can quantify emissions from land-use change more realistically, and the model is now also able to quantify the natural CO₂ uptake by terrestrial ecosystems. As part of the NextGenCarbon project, we are working on integrating the effects of natural disturbances (e.g., windthrow, forest fires, insect outbreaks) into BLUE and refining its growth curves for forests. Together, these improvements will contribute to more realistic estimates of carbon uptake through forest regrowth.