Verbiest, W.,  Ewango, C.,  Makana, J-R.,  Lewis, S.,  Fayolle, A.,  Gorel, A-P.,  Bastin, J-F.,  Meunier, F.,  Sitch, S.,  Friedlingstein, P.,  Smallman, L. & Hubau, W. 2024. ‘Synthesis of national carbon fluxes of African rainforest countries’. Ghent Africa Plateform Symposium (GAPSYM17). Book of abstracts.

Résumé de colloque

African tropical ecosystems possess great potential for nature-based solutions in mitigating anthropogenic greenhouse gas emissions and biodiversity loss. However, past studies mostly focused on pan-continental carbon balance quantification, often ignoring regional differences. Remarkably, few science-informed attempts have been made to refine national-level carbon flux estimates within African rainforest countries. Yet, such refined estimates are essential to improving the quantification of Nationally Determined Contributions for the United Nations Framework Convention on Climate Change. Here, we present preliminary results on quantifying national carbon budgets for African rainforest countries, disentangling four major carbon fluxes for 2003-2019: (1) the net carbon uptake in intact tropical terrestrial ecosystems, (2) land-use change fluxes, 3) CO2 outgassing in inland waters, and (4) fossil fuel emissions. The net carbon uptake in intact terrestrial ecosystems is based on Dynamic Global Vegetation Models TRENDY v111,2 (DGVMs), ground-based data (AfriTRON3 ), CARDAMOM4 , and remote sensing data products of Net Primary Productivity5 and soil heterotrophic respiration6-7. Land-use change emissions are calculated using bookkeeping models (BLUE8 , H&N20179 , OSCAR10), DVGMs1,2, and CARDAMOM4 . Additionally, we estimate carbon emissions from land-use change by analyzing various satellite images and related products providing data on land-use change11–12, soil and tree carbon stocks13–18, fire emissions19–20, and carbon recovery in regrowing forests21–22 in tropical Africa. We also quantify carbon emissions from CO2 outgassing in estuaries23 and inland waters24-25. National carbon balances are completed by using data on fossil fuel emissions from the Global Carbon Project2 . Besides calculating national-level net carbon fluxes using a bottom-up approach by summing individual carbon fluxes, we quantify the net carbon flux using a top-down approach based on atmospheric inversion models (GCP-GridFED26, CAMS27, Jena CarboScope28 , MIROC4-ACTM29, NISMON-CO2 30). We reveal that carbon balances of African rainforest countries remain highly uncertain. Our bottom-up estimates show that Congo Basin countries are net carbon sinks, while most West-African countries are net carbon sources. In contrast, our top-down estimates of net carbon fluxes indicate that African rainforest countries are net carbon sources. Overall, tropical terrestrial ecosystems have played an important role in mitigating anthropogenic carbon emissions in African rainforest countries. Our insights into nation-level carbon fluxes will be crucial for informing African rainforest countries, guiding climate policies to help stay on track to keep global warming well below 2°C.