A first count of trees in Africa's drylands has enabled scientists to calculate how much carbon they store and could help devise better conservation strategies for the region and beyond, a study said Wednesday. The number of trees in the vast region—the count came to nearly 10 billion—has not been known up to now, and the new data could prove crucial for slowing or preventing desertification, the authors said. The data show there are 9.9 billion trees within Africa's drylands: semi-arid Sub-Saharan Africa north of the Equator, which includes the Sahel and covers nearly 10 million square kilometres (four million square miles) of land from the Atlantic Ocean to the Red Sea. The researchers used machine learning to scan more than 300,000 high-resolution satellite images to map the crown area of individual trees in the drylands, defined as an arid region with low rainfall. The authors hope to improve on the tool in the future by being able to map the trunk of the tree to determine its age and height, allowing for more accurate data on carbon storage capacity.