My theory on Mayan collapse

The Mayan civilization colallapsed because they didn't practice crop rotation and the soil ran out of nutrients. People (some are descendants of the Maya,) still grow corn in the area around Copán City, and report a smaller harvest each year. The Mayans had so many people to feed that they were farming the land every single season, not leaving any time for the earth to build up nutrients. The modern farmers get the same results when using that method. The land eroded because it was being farmed too much. Landslides could have ruined small communities, not to mention decreased the amount of farmable land. Eventually, the crops ran out and the people didn't have enough to eat. Decrease in harvest from both these causes in turn led to malnutrition among the Mayan people. Since the Mayans ate chiefly corn, there was a lack of iron in the Mayan diet. About 80% of the skulls found at Copán have evidence of anemia because the Mayans didn't have a balanced diet. If anemia and starvation didn't kill off the Mayans, then the results of those two ruined the gene pool of future generations, making it harder and harder for the Mayans to survive.

This is an order of crop rotation with just corn. In the spare areas, a different crop could be planted as well such as potatoes. If the Mayans had used this method, they would have survived for longer.

Imagine if this kind of erosion happened right under your house! This is a modern day example of erosion in the mountains that the Mayan farmers could have experienced. The Mayan huts were probably even smaller than the modern house in the top of the photo!

This is a picture of a Mayan skull found near Copán. The rough textured areas are signs of anemia caused by the people's unbalanced diet.