What became known as the gold of the north

explanation:

north america's importance as a region began to grow exponentially when the region became using tobacco as an important export. this product was termed to be the gold of north america and permitted the region to gain popularity, monopoly and lots of foreign exchange from such trading activities.

they died because of a disease during the first spanish colonies.

climate change is the big reason to the decline of the indus valley which also caused floods. so i dont know what answer would best fit the description thats just what i found online! have an awesome