Projected Rainfall‐Driven Expansion of Woody Cover in African Drylands

• Published in: Geophysical research letters 2023-08, Vol.50 (15), p.n/a
• Main Authors: Zhang, Wenmin, Fensholt, Rasmus, Brandt, Martin
• Format: Article
• Language: English
• Subjects: Annual precipitation; Arid lands; Arid zones; Atmospheric models; Carbon dioxide; Climate change; Climate change mitigation; Climatic extremes; Ecosystem structure; Ecosystems; Encroachment; Future climates; Future precipitation; Humid areas; Intercomparison; Modelling; Precipitation; Rainfall; Rainfall-climatic change relationships; Satellite observation; Satellites; Stocks; Terrestrial ecosystems; Wildfires
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL103932

Projection of future woody cover is essential to understand potential changes in structure and functioning of terrestrial ecosystems. Previous studies mapped woody cover during historical periods observed by satellites, however, it remains unclear how woody cover is expected to change in response to future climate change. Here, we develop data‐driven models to predict woody cover in Africa using multiple environmental predictors and show that woody cover can be accurately modeled using Random Forest. Empirically‐based simulations forced by precipitation from CMIP6 project an overall increase in woody cover at the continental scale by 2100. However, increases are mainly occurring in regions with annual precipitation less than ∼1,600 mm y−1, whereas woody cover is predicted to decrease in areas of higher rainfall. Our results suggest that climate change may alter the functioning of dryland ecosystems by continued woody encroachment and cause a loss of carbon stocks in humid areas. Plain Language Summary Future climate changes pose a severe threat on the structure and functioning of terrestrial ecosystems and thereby threaten human well‐beings. Forests play a critical role in mitigating climate changes by absorbing atmospheric CO2, but undergo large losses during last three decades due to a range of disturbance, such as wildfires and extreme climate events. In particular, forest and non‐forest trees are largely impacted by changing precipitation regimes in Africa, but the knowledge on this is limited to current periods observed by satellites. Here, we establish a data‐driven model by linking woody cover to environmental variables, the developed model was further forced by future precipitation from the Sixth Coupled Model Intercomparison Project. We predict an increase in woody cover in drylands by the year 2100, while a decrease in humid areas across African continent. This study thus provides a feasible data‐driven approach for the prediction of woody cover without the temporal limitation of satellites and allows for a better understanding of changes in ecosystem structure, composition and functioning in the context of future climate change. Key Points Woody cover can be accurately predicted with environmental variables Mean annual precipitation explains the most spatial variability in woody cover in Africa Predicted precipitation changes will increase woody cover in drylands but decrease woody cover in humid areas by 2100