Editing IPCC:AR6/WGII/Chapter-9 (section)

==== 9.6.2.1 Projected Biome Distribution ====

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The geography of African biomes is projected to shift due to changes in atmospheric CO 2 concentrations and aridity (Figure 9.18). Grassland expansion into the desert, woody expansion into grasslands and forest expansion into savannas are projected for areas of reduced aridity, caused by reduced moisture stress from CO 2 fertilisation under medium (RCP4.5) and high (SRES A2) emissions scenarios ( [[#Heubes--2011|Heubes et al., 2011]] ; [[#Moncrieff--2016|Moncrieff et al., 2016]] ). This greening trend may slow or reverse with continued temperature increase and/or in areas of increased aridity ( [[#Berdugo--2020|Berdugo et al., 2020]] ). The net impact of these effects on vegetation is highly uncertain ( [[#Trugman--2018|Trugman et al., 2018]] ; [[#Cook--2020a|Cook et al., 2020a]] ; [[#Martens--2021|Martens et al., 2021]] ). The maintenance or re-establishment of natural fire and large mammal herbivory processes can mitigate projected CO 2 and climate-driven changes ( [[#Scheiter--2016|Scheiter and Savadogo, 2016]] ; [[#Stevens--2016|Stevens et al., 2016]] ). Expansion of croplands and pastures will reduce ecosystem carbon storage in Africa, potentially reversing climate- and CO 2 -driven greening in savannas ( [[#Aleman--2018|Aleman et al., 2018]] ; [[#Quesada--2018|Quesada et al., 2018]] ).

Vegetation growth simulated by dynamic vegetation models is often highly sensitive to CO 2 fertilisation. These models project the African tropical forest carbon sink to be stable or strengthened under scenarios of future climate change ( [[#Huntingford--2013|Huntingford et al., 2013]] ; [[#Martens--2021|Martens et al., 2021]] ). In contrast, statistical modelling suggests it has begun to decline and will weaken further, decreasing from current estimates of 0.66 tonnes of carbon removed from the atmosphere per hectare per year to 0.55 tonnes of carbon ( [[#Hubau--2020|Hubau et al., 2020]] ). Increasing rainfall seasonality and aridity over central Africa ( [[#Haensler--2013|Haensler et al., 2013]] ) threatens the massive carbon store in the Congo Basin’s Cuvette Centrale peatlands, estimated at 30.6 billion tonnes ( [[#Dargie--2019|Dargie et al., 2019]] ).

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