A landmark new study has found that, in the last decade, the African continent has started emitting more carbon than it stores. When the total amount of carbon that is sequestered by natural ecosystems (such as the soil and plants in grasslands, savannas and forests) exceeds the amount of total carbon emissions within a system, it’s referred to as a net sink of carbon. But, the study found, as natural ecosystems are converted for agricultural purposes, the carbon storage capacity is decreasing – while the rate of emissions is increasing. Yolandi Ernst of the University of the Witwatersrand (Wits) in…