The southern Sahara and the Sahel are home to more trees than thought, which have a "crucial role" in biodiversity and people's lives. An international research team has developed an artificial intelligence (AI) pattern recognition program to count trees with a plant surface of more than 3 square meters, from over 11,000 high definition satellite images, AFP reported.
Over an area of 1.3 million square kilometers in the south of the Sahara, the Sahelian strip, and sub-humid zones in West Africa, they were able to count more than 1.8 billion trees, the researchers wrote in the journal Nature.
Based on the findings, the average tree number is 13.4 per hectare, with a median plant cover of 12 square meters. The researchers noticed that this vegetation, certainly sparse, "plays a crucial role for biodiversity and for the ecosystem as carbon storage, food resources, and shelter for human and animal populations."
"Although the total vegetation cover is low, the relatively high density of isolated trees calls into question the prevalent idea of desertification of drylands, as even the desert could offer a surprising density of trees," they added. The density increases as it descends towards the wetter areas in the south, from 0.7 trees per hectare in the "hyperarid" areas to 9.9 in arid zone, 30.1 in semi-arid zone, and 47 trees per hectare in subhumid zone. In addition to this count, the study offers a new method to study the presence of trees outside dense forest areas, and in particular their role in climate change mitigation and potentially poverty, through their contribution to agricultural systems.
"This kind of data is very important to establish a base. And in two or ten years, we could repeat the study to see if efforts to revitalize vegetation are effective", one of the researchers, Jesse Meyer from the NASA explained in a statement.
"The used artificial intelligence technique also suggests that it will soon be possible, within certain limits, to map the location and size of all trees. This information is fundamental to our understanding of ecology on a global scale," estimated Niall P. Hanan and Julius Anchang of the University of New Mexico, in an analysis of the study.