sentences:  Some areas are estimated to have had ca 2,000 people/km².Mesoamerican agriculture was very extensive, and there is some evidence suggesting that the land was depleted by unsustainable overfarming, resulting in a famine which was an important factor in the collapse of the Classic Maya states of this area.The population is estimated to have dropped by two-thirds between the mid 9th century and the mid 10th century.