Carbon balance of tropical forests at the largest scale

The aim of Pillar 2 is to produce a synthesis of CO₂ and CH₄ flux balances for Central African forests, by integrating data from Pillar 1 and Pillar 3, and to make a strategic contribution to improving existing and future flux measurement observation systems based on flux towers and atmospheric concentration measurements established with the OFVi partnership countries and international scientific partners. Flow towers enable continuous monitoring of greenhouse gas and energy exchanges at the level of representative forest canopies, in order to understand processes such as the response to drought. These local measurements can be combined with satellite data and climate variables to map fluxes on a larger scale, and are also used to evaluate satellite data on primary productivity fluxes. The network of flux towers is especially incomplete for the Central African region. Atmospheric measurements of carbon dioxide are collected from ground stations, airborne profiles, ground-based remote sensing instruments that measure the abundance of concentrations in the air column and satellite data. In Central Africa, there are as yet no continuous observatories for monitoring atmospheric concentrations, and it is important to be able to install new stations as part of international collaborations. Inversions can be used to diagnose flux balances over large regions, but require observations to be accurate. Inversions provide an overall constraint on all greenhouse gas emissions and absorptions in a region, and must be supplemented by ground measurements, or by the results of vegetation models to attribute net balances to different causes, such as deforestation, degradation and forest regrowth. The only region where scientists have sufficiently dense in-situ data to estimate the global net carbon balance is the Brazilian Amazon, using repeated measurements of CO2 collected by aircraft and data from flux measurement towers. Pillar 2 involves one-off campaigns and a strategic contribution to existing observation schemes aimed at developing similar measurements for tropical forests in Central Africa. This net carbon and methane balance is an essential requirement for all mapping activities and provides an independent assessment of net carbon emissions from the land sector. These data should eventually be integrated across the Amazon, Central Africa and tropical Asia.

Publications :

Ernst, Y., Archibald, S., Balzter, H., Chevallier, F., Ciais, P., Fischer, C. G., ... & Scholes, R. J. (2024). The African regional greenhouse gases budget (2010–2019). Global Biogeochemical Cycles, 38(4), e2023GB008016. https://doi.org/10.1029/2023GB008016

Mostefaoui, M., Ciais, P., McGrath, M. J., Peylin, P., Patra, P. K., & Ernst, Y. (2024). Greenhouse gas emissions and their trends over the last 3 decades across Africa. Earth System Science Data, 16(1), 245-275. https://doi.org/10.5194/essd-16-245-2024.