They began building huge temples that required considerable resources, especially large, straight trees whose wood could withstand the weight of tonnes of stone. Their choices were limited to two types of trees only.

'So, unfortunately, Jasaw Chan K'awiil tapped into their sacred groves to do this,' said Lentz.

So what led to the downfall of the Mayans?

'When you clear all the forests, it changes the hydrologic cycle,' said Lentz. 'That causes soil erosion, which then chokes the rivers and streams. With no trees, you lose water retention in the soil or aquifers so the ground dries up.'

Besides using the trees as timber, the Mayas also burned the trees, adding carbon to the air in the form of carbon dioxide. Trees remove carbon dioxide from the air and return oxygen in its place, thus cleaning and purifying the air.

'We're saying in the end they were unsuccessful,' said Lentz. 'But they kept it going for several hundreds of years -- so they must have done some things right.'

These findings were published in the July issue of the Journal of Archaeological Science.