Why you think it was the main reason

the dust bowl, otherwise known as the dirty thirties, was a huge dust storm that killed multiple (and i mean  multiple) farmer's crops, leaving them homeless, and foodless, and jobless. in california, there were 5.7 million residents, and the population shrank as mexicans were repatriated. however, when the dustbowl happened, a lot of people began to move to california. by 1940, 250,000 people had arrived. therefore, your answer would be  the population increased, massively.  i hope this !

explanation:

the effect of the ming leaders banning ships with more than two masts was that there was no further construction of ships masts, because there was a surplus. ming emperors disallowed foreign exploration