1. Some are of the opinion that the invasion of the Aryans was the cause for the decline of Indus valley civilization.
2. Change of course of the river Indus changed the area into the sand and affected the fertility and this led to the decline of the Indus valley civilization.
3. Due to changes in climatic conditions, the area lost fertility and people were compelled to move to another area.
4. Constant use of firewood for brick manufacture caused deforestation and low rainfall.
