The words contained in this file might help you see if this file matches what you are looking for:

...Great civilizations built due to soil mesopotamia nile mayan green revolution bc fertile crescent around the soils between tigris and euphrates land rivers irrigated agriculture destroyed by salts source https bftaxhelp wordpress com about property taxes history of ancient river was foundation for continual flooding deposited thick known as kemet black lands http www rivervalleycivilizations php responsible survival growth economic success deforested cities crops initial high fertility rapid decrease in productivity fao org docrep if htm poor collapse erosion degradation worldwildlife modern day improved agricultural practices management plant genetics increased yields challenges...