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Researchers from the University of Amsterdam have demonstrated that the climate in South Mexico changed following the collapse of the Maya empire. From preserved pollen grains the paleoecologists could deduce that the climate quickly became dryer.

The climate becoming dryer, explains the decrease in the population following the collapse of the Maya empire. The climate researchers have therefore helped to solve an archaeological mystery.

With the help of pollen grains, the paleoecologists from Amsterdam could accurately reconstruct the climate in a certain region. Each plant will only grow under certain conditions. By working out the overlap between the possible growth conditions for each plant in an area, an accurate picture of the local climate can be constructed.

In the area inhabited by the Mayas, Southern Mexico and Northern Guatemala, the researchers found that round about 1000 AD the climate quickly became dryer. This was about 100 years after the collapse of the Maya empire. The researchers suspect that after the collapse of the well-organised empire, the inhabitants destroyed many wildlife and agricultural areas. This led to erosion, as a result of which the evaporation, and thus the rainfall, decreased.

The pollen grains also provided information about farming in the distant past. In Peru the paleoecologists could reconstruct how the cultivation of maize and grain crops spread over various population groups. Certain population groups who lived as hunters and gatherers when the Spaniards arrived, were revealed to have a rich agricultural past.
The pollen research in South and Central America has also provided data that are important for current climate research. In an elevated area in Colombia, pollen grains were found from the last three million years. The paleoecologists examined which plants grew at various carbon dioxide concentrations in the atmosphere over the past 450,000 years. The carbon dioxide concentration in the air for this period is known, thanks to the discovery of frozen air bubbles in ice at the South Pole. The comparison revealed that in the past, plant growth was strongly correlated with carbon dioxide concentrations. The analyses revealed that not only the temperature changed but also the precipitation and the season in which this fell.