Deforestation and the Maya

   

Literature is abundant on the collapse of the Mayan civilization - during the ninth century A.D. - ranging in focus from foreign invasion and social turmoil to disease epidemics, climate change and collapse of trade. One of the most widely accepted theories is that human induced drought conditions played a key role in bringing about the abandonment of the once flourishing Mayan cities. This view is supported by the article of Oglesby et al. (2009), Collapse of the Maya: Could deforestation have contributed?, which argues that major and prolonged drought conditions were the main factor that led to the rapid decline of the Maya as water resources were key for their survival, especially during the long dry season. Nonetheless, the article acknowledges that the collapse may have been brought about by a combination of factors where social and political circumstances may also have played a role.  While to some extent these drought conditions could have resulted form natural variability, Oglesby et al. argues that deforestation is likely to have played a key role.

The Mayan civilization had by 600 B.C. significantly altered the landscape of present day northern Guatemala and have cut down a large proportion of the forest of the area to accommodate agricultural expansion. By 900 A.D. most of the forest was gone. The peak of the Mayan civilization, between 600 and 850 A.D., was followed by a drastic decline and eventual collapse in little more than a century. Oglesby et al. notes that the only cities where humans survived the collapse were the few with stable sources of drinking water instead of dependence on surface reservoirs for water, a feature of the majority of Mayan settlements.

 

Research around the Holmul river that runs along many of the major Mayan cities suggests that between 750 and 850 A.D. the river either dried up or became very swampy.  This correlates with other research that indicates major drought at 750 A.D. as well as intense multi-year droughts between 810 and 910 A.D. The cause of these droughts is still widely debated. Some attributes it to natural climatic variability while others advocate the notion of human induced vegetation change. According to Oglesby et al. it is most likely a combination of the two. They show that deforestation of Mesoamerica has major impacts on temperatures and precipitation which, considering the almost complete deforestation by the Maya, can not be ignored. While effects of deforestation on temperatures and rainfall patterns can be observed both in the dry and the wet seasons they are considerably stronger in the wet season. The Maya depended on storage of water from the wet season to use during the dry season. Therefore, Oglesby et al. states, reduced rainfall and increased temperatures during the wet season may have been a bigger stress factor than more pronounced drought conditions during the dry season and might have eventually led to the rapid collapse of the Mayan civilization.