The main impact De Soto's expedition was disease.The Native Americans did not have any immunity to European diseases since they had never been in contact with them. The most detrimental of illness was the smallpox. They also were introduced to animals such as horses, war dogs, and pigs.
The answer is a decrease in the usability of soil for agriculture.
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The Umayyads were the first Muslim dynasty, established in 661 in Damascus.
