"The cities tried to keep an 18-month supply of water in their reservoirs," says Sever. "For example, in Tikal there was a system of reservoirs that held millions of gallons of water. Without sufficient rain, the reservoirs ran dry." Sever said.
Mass graves of suspected elites suggest political revolt against a top-heavy and ineffective royal system. At the time of the decline, the Maya had cleared huge swaths of land entirely of trees. It took 20 trees to create enough heat for just one square meter of limestone plaster for their temples and buildings. The destruction of trees for construction and to clear space for corn, was the cause of their downfall.
NASA's satelites were able to identify hundreds of previously unknown Maya sites that helped paint a complete picture of the expansive culture.