Ecological failure and infrastructural breakdown is a new alternative theory regarding the end of the Khmer Empire. Scientists working on the Greater Angkor Project believe that the Khmers had an elaborate system of reservoirs and canals used for trade, transportation, and irrigation. The canals were used for harvesting rice. As the population grew there was more strain on the water system. During the fourteenth and fifteenth centuries, there were also severe climatic changes impacting the water management system. Periods of drought led to decreases in agricultural productivity, and violent floods due to monsoons damaged the infrastructure during this vulnerable time. To adapt to the growing population, trees were cut down from the Kulen hills and cleared out for more rice fields. That created rain runoff carrying sediment to the canal network. Any damage to the water system would have enormous consequences.