The correct answer is <span>A wet summer caused outbreaks of plant disease
The plants were not used to such a wet and humid summer because it had not been such traditionally. They could not adjust to this because the plant diseases that could prosper in such humid areas started developing rapidly and completely ruining all crops which led to the great famine which ended countless lives.</span>
While it is difficult to determine exactly how many Natives lived in North America before Columbus, estimates range from a low of 2.1 million to 7 million people to a high of 18 million.
