How land-use change affects carbon storage in Africa

There are conflicting ideas about the development of rural Africa: On the one hand, governments and conservation organizations want to protect savanna ecosystems in order to preserve the habitat and migration areas of wildlife such as elephants and lions. On the other hand, the local population’s food supply is based on farming, meaning that their future livelihood can only be secured through expanding or intensifying agriculture—also as a result of climate change.

As drylands are the largest terrestrial carbon sink, these visions of the future have a significant impact on global carbon storage. “However, the storage potential of savannas has not yet been sufficiently researched and their carbon dynamics with regard to disturbance factors such as browsing by elephants, woodcutting and livestock herding are poorly understood,” says Dr. Liana Kindermann, author of a new study published in Global Change Biology.

She and her team developed a method to estimate carbon storage in such disturbed ecosystems and quantified the carbon in trees, shrubs and their roots as well as the organic carbon in the soil.

“We take a look at a few representative locations to see how today’s land-use decisions could change the entire landscape in the future. We process this data with powerful statistical models to assess the impact of future land-use change on above-ground carbon and carbon storage across the entire ecosystem,” Liana Kindermann says. “Our results show that the vulnerability of carbon reservoirs to disturbance varies greatly depending on the land-use scenario,” she says.

With increasing wildlife density, aboveground carbon storage in shrubs and trees decreases by an average of 14% to 55%; with agriculture, the carbon loss is as high as 73% to 94% compared to sites with little disturbance.

The organic carbon content in the soil can actually be increased through disturbances, especially when herbivores such as elephants feed on aboveground vegetation and thus redistribute carbon into the soil. However, this process is limited and can only work as long as the vegetation remains stable and is not destroyed by excessive wildlife densities.

The carbon content in the soil is important for agricultural use. This is also evident from the observation that agricultural areas were primarily created where the soils already contained more carbon.

Decisions on how the land area is to be used in the future—also in terms of wildlife conservation—change the functions and ecosystem services of the savanna. “Occasional and localized disturbance of vegetation by large browsing wildlife species and livestock grazing has a positive effect on carbon storage in the savanna if the vegetation is allowed to recover.

“Extreme interventions such as large-scale deforestation for agriculture, but also chronically high wildlife densities, disbalance the carbon cycle and are detrimental to environmental protection and people’s livelihoods. Sustainable strategies for future land-use therefore require transparent consideration of such trade-offs and sustainable solutions for everyone,” says Kindermann.