https://pubs.usgs.gov/pp/0454h/report.pdf (page 5, Start at “Introduction”)
https://news.un.org/en/story/2022/07/1123462 (“It also takes around a thousand years to create just a few centimetres of topsoil and to help land restoration.”)
https://news.un.org/en/story/2022/07/1123462 (“It also takes around a thousand years to create just a few centimetres of topsoil and to help land restoration.”)