<human>:  How did the Mayan civilization collapse?
<bot>: The Mayan civilization of Central America collapsed around the 8th or 9th century CE, possibly due to a combination of factors such as protracted drought, overpopulation, and political upheaval. It is believed that increasing environmental degradation caused by deforestation and soil erosion may have played a role in the decline of the Mayan civilization. There is also evidence that civil wars, which consecutively weakened the Mayan city-states, could have caused the decline.