Yolandi Ernst of the University of the Witwatersrand (Wits) in South Africa led the international research team that calculated the flows of carbon dioxide, methane and nitrous oxide through Africa’s terrestrial and aquatic ecosystems. She and one of the study co-authors, Sally Archibald – also from Wits and the lead of the Future Ecosystems for Africa Programme – unpacked their findings for The Conversation Africa.
This study formed part of a global effort by the Regional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project. It aims to establish improved greenhouse gas budgets for large regions covering the entire globe at the scale of continents (or large countries) and large ocean basins.
The net budget estimate was the result of adding all the sources and sinks, just like balancing a household budget, where you don’t want to be spending more than you are earning.
This information is crucial for policy making. If scientists, land managers and NGOs know which activities produce the most greenhouse gases they can work with governments and policymakers to minimise this. And knowing which parts of Africa best help to store carbon means funding and policy efforts can be directed to protecting and increasing this carbon “land sink.’
It’s important to distinguish between anthropogenic and natural emissions here. Fossil fuel burning and agriculture are the biggest sources of carbon emissions; both are anthropogenic (caused by humans). Other emissions are part of the ecosystem functioning but they can also be affected by human activities. Examples include fire, methane emissions from herbivores, and inland and coastal water bodies. These all represent quite large emissions, but they’re only somewhat affected by human activities.
In Africa’s case, our budget shows that when people transform natural landscapes for agricultural and other purposes, the emissions from fire decrease, but emissions from herbivores increase.
There are also some important natural processes that draw carbon and greenhouse gases back into the land surface. These include the growth of vegetation and soil carbon storage, as well as weathering of rocks (which turns atmospheric CO₂ into carbonate minerals), and burial of carbon in the ocean.
The previous African carbon budget (1985-2009) showed the processes drawing carbon into Africa were higher than the natural emissions and the anthropogenic emissions. The continent was a carbon sink even though it emitted some anthropogenic greenhouse gases: Africa was providing a climate service to the globe.
Globally the anthropogenic emissions of CO₂ are 11.21 gigatons of carbon per year (GtC/yr), but the land takes up about 3.5 GtC/year, so it is helping to slow the growth rate. The African land sink is about 0.8 GtC, representing about 20% of the world’s total land sink.
A Guest Editorial