Uncertainties of climate and CO2 impacts on carbon stocks and biome distribution in Africa

Abstract

<p>Climate change is expected to cause vegetation change in Africa, with profound impacts on ecosystems and biodiversity. Projections of future ecosystem states are constrained by uncertainties regarding relative impacts of climate change and CO<sub>2</sub> fertilisation effects. Rising atmospheric CO<sub>2</sub> drives climate change, but also directly affects plant physiological functions via carbon uptake, carbon allocation, water use efficiency, and growth. We use the adaptive Dynamic Global Vegetation Model (aDGVM) to quantify uncertainties in projected African vegetation until 2099. High-resolution climate forcing for the aDGVM, was generated by regional climate modelling. An ensemble of 24 aDGVM simulations based on six downscaled General Circulation Models (GCMs) under two Representative Concentration Pathways (RCPs 4.5 and 8.5) with plant-physiological CO<sub>2</sub> effects enabled and disabled was implemented.</p><p>Under strong climatic change with high CO<sub>2</sub> increases (RCP 8.5), almost a third of terrestrial Africa is projected to experience biome changes with woody encroachment into grassy biomes dominating biome changes. Projections under medium-impact scenarios (RCP 4.5) still predict biome changes for around a quarter of Africa. With climate change only and elevated-CO<sub>2</sub> effects disabled, woody encroachment is weak and reduction of forest cover in favour of savannas prevails. Change in aboveground vegetation carbon until 2099 varied from a strong increase under elevated CO<sub>2 </sub>(61.5%, RCP 8.5; 33.9%, RCP 4.5) to a small increase of 5.4% (RCP 4.5) and a decrease of -13.6% (RCP 8.5) without CO<sub>2</sub> effects.</p><p>CO<sub>2</sub> effects in combination with RCP scenarios caused the greatest uncertainty in projected ecosystem changes. Downscaled GCM projections caused weaker uncertainties in the simulations. Future biome changes due to climate and CO<sub>2</sub> change are therefore likely in large parts of Africa. Their magnitude and location often remain uncertain. Climate mitigation and adaptation response measures that rely upon vegetation-derived ecosystem services will need to account for alternative climate futures.</p>

Co-occurrence of climate-change induced and anthropogenic pressures in Central American key biodiversity areas

“…(Smith et al 2014(Smith et al , 2001, also see https://web.nateko.lu.se/lpj-guess/), which has been applied in numerous climate change impact studies before (e.g. Hickler et al 2012, Seiler et al 2015, Hof et al 2018, Martens et al 2021. This dynamic global vegetation model operates at the level of plant functional types (PFTs) and models main physiological and ecosystem processes in relation to climatic and edaphic drivers at stand scale (for a detailed description see supplement).…”

Characterising the response of vegetation cover to water limitation in Africa using geostationary satellites

“…Moreover, African ecosystems contribute strongly to fluctuations of the global carbon cycle (Williams et al, 2007;Weber et al, 2009;Valentini et al, 2014;Palmer et al, 2019). Despite its importance, large uncertainties prevail in understanding the African ecosystems and quantifying spatiotemporal variations of their functioning due to the complexity of continental gradient and scarcity of ground measurements, which has been shown in studies using different data and approaches ranging from in-situ observations (Schmiedel et al, 2021), over remote sensing (Weerasinghe et al, 2020), to ecosystem modelling (C. Martens et al, 2021), as well as systematic literature reviews (Adole et al, 2016).…”