Yeah, but 90%????
Somewhat related --
Years ago I saw an article which lamented the enormous decline in Sperm Whale populations due to past whaling. The article stated that at one time the Sperm Whale population may have been as much as 150,000! But, alas, because of our terrible whaling, the population was greatly reduced today and we did not know how endangered these great beasts were. Fortunately, a new survey was planned that might provide accurate numbers for the current population.
A follow-up article stated that a new survey had been performed and -- alas! -- the current population of Sperm Whales was estimated at a measly 160,000! Pitiful! Deplorable! Oh, the devastation we have wrought! Experts estimated that at one time the population may have been as much as 350,000 ...
It is very hard to know what the populations were. No one took counts at the time.
Coronado found vast swaths of land that had very few people in them.
That was about 1540, about 50 years after Columbus' first contact.
Hernando de Soto was exploring up from Florida at the same time, and found some fortified villages, but no cities.