Ruins in the jungle and in the desert indicate that cities come and go. Are cities sustainable in the long run? Do they have a life time? Or should we expect them to come and go? We might learn about possibilities by looking at a classic case history.
Classic period 300-900 A.D.
During this period there was development of extensive city-states. Examples include Palenque, Chichen Itza, Copan, and Tikal. These had large ceremonial centers. Most of the buildings were built from limestone blocks quarried from the local bedrock. Tikals population has been estimated at 60,000 to 100,000 within the city proper, an estimated population density greater than many modern American and European cities. Estimates of the size of the peak Mayan population in Central America range from 3-13 million. This was supported by agriculture based on sophisticated irrigation techniques that utilized reservoirs. An extensive road network existed. For many of these cities, cenotes (sinkholes) were the only year round source of water. This is because in a karst terrane, fissure openings and cave systems are so efficient at capturing the water, that there is no subsurface drainage, no streams and rivers to speak of.
Map of Mayan cities.
Chichen Itza occupied from 500-900 A.D. and then abandoned for one hundred years, before it was rebuilt. It was abandoned again in 1300 A. D.
By 900 A.D. the city-states were abandoned. There is debate about the exact history, but many researchers use the term collapse. The question that can be posed is what led to this abandonment.
Ideas for the 'demise' of the city states and assumed demographic collapse.
Basically it is a debate as to whether it was due to external, environmental factors or due to internal, social factors. Certainly the former can trigger changes in the latter. Some possibilities include:
Annenberg lecture on the reason for the Mayan collapse.
How might these various ideas be tested?
How might these ideas be applied to modern cities, if at all?
Can you develop a system model for a city?
Transportation efficiency as a crucial parameter, as need to bring in basic resources of food, water, and building supply, and take away wastes.
Perhaps urban cores die as new cities nucleate on the growing periphery.
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