Africa, despite its large area and thus large impact on the global carbon cycle, is relatively unexplored with respect to ecosystem functions and impact on climate change. The Sahel is a region in Africa, and it is one of the largest semi-arid savannah regions in the world, serving as a transition zone between the Sahara Desert to the north and the humid Sudanese savannah to the south. This area is characterized by a sparse canopy of trees and shrubs, with a grassy understory as the dominant vegetation.
Now, one of few in situ studies over a long period of time, 2010-2022, shows that the Sahel area has lost a lot of its power as a carbon sink during the time period examined.
This study examines carbon dioxide exchange in Sahel by analysing data from eddy covariance measurements on site. The eddy covariance method measures flows of greenhouse gases, providing a detailed picture of how much carbon is sequestered in the ecosystem and how much is released back into the atmosphere.
Drought stress and unpredictable rainfall patterns
The results from the measurements show a clear decline in carbon sequestration strength during the studied period. Researchers observed that the average CO2 uptake decreased, indicating that the savanna's ability to function as a carbon sink has weakened. This decline is particularly noteworthy given global warming and its impact on ecosystem health and stability.
A central factor behind the decreased carbon sequestration is the increasing drought stress caused by climate change. The study shows that temperatures have risen and that rainfall patterns have become more unpredictable. These changes affect both vegetation and the soil’s ability to store carbon. Additionally, changes in land use, such as overgrazing, have further contributed to reduced carbon sequestration.
Another important observation from the study is that seasonal variations in carbon dioxide flows have become more extreme. This can lead to increased uncertainty in future carbon sequestration forecasts, which is significant for global models aimed at predicting the carbon cycle and its impact on climate.
Potential consequences for global climate strategies
The conclusions from the study point to a critical situation for African savannas, which play an important role in the global carbon cycle. The decreased carbon sequestration strength in these ecosystems can have far-reaching consequences, not only for local environments but also for global climate strategies. The researchers emphasize the need to monitor these changes closely and suggest that conservation efforts and sustainable land use can help improve carbon sequestration and protect these valuable ecosystems.
In this context, it is crucial to integrate these findings into policy development and planning to address climate change. The study highlights the importance of understanding the complexity of ecosystems' responses to climate change and how human activities can influence these processes.
Read the article "Eddy covariance measurements reveal a decreased carbon sequestration strength 2010–2022 in an African semiarid savanna" in Global Change Biology