Incited Wars Among the Classic Maya- A new study of the relationship between climate change and clashes among the Classic Maya explicitly links temperature increases with growing conflicts

Does a warming world beget more wars? A new study that investigates the relationship between climate change and clashes among the Classic Maya believes so, drawing an explicit link between temperature increases and growing conflicts. The study, published in Quaternary Science Reviews, examined about 500 years of Maya history, from 363 to 888 AD. This is the so-called Classic period in which the Mesoamerican civilization boomed, with its people constructing extensive cities and massive pyramids, as well as developing one of the earliest writing systems in the Americas. Indeed, the Maya began a tradition of recording historical events on stone monuments.  
The researchers cataloged inscriptions on monuments related to violent struggles and compiled temperature and rainfall records for the regions inhabited during the Classic period: the lowlands of the Yucatán Peninsula, which includes parts of southern Mexico, Guatemala, and Belize. A total of 144 unique conflicts emerged from inscriptions on monuments from more than 30 major Maya centers. The research team then compared conflict records to palaeoclimate data, and the correspondence was impressive. The change in conflict levels between 350 and 900 AD was considerable. The number of conflicts increased from 0 to 3 every 25 years in the first two centuries to 24 conflicts every 25 years near the end of the period. They noted the exacerbation of conflicts could not be explained by change in the amount of rainfall. It was instead associated with an increase in summer temperature.
Experts think that there are two potential mechanisms by which increases in temperature can lead to greater conflict. One is psychological — when temperatures rise, tempers shorten. Several studies suggest it is possible that increased average summer temperatures made the Classic Maya more bellicose. The other mechanism, is economic, and involves the staple crop for the Classic Maya: maize. Throughout the Classic period, average temperature fluctuated between 82.4 degrees Fahrenheit (28 degrees Celsius) and 84.2°F (29°C). During periods when the temperature was around 82.4°F (28°C) or less, maize yields were reasonably stable, with little or no food shortage and little conflict. But as temperature continued to rise and the region experienced days at or above 86°F (30°C), crop shortfalls occurred frequently. Large-scale deforestation throughout the Classic period caused by urban expansion worsened the effect, increasing regional temperatures by reducing soil moisture availability. The result was food shortage, which led to spiking levels of conflict. With declining maize yields, a ruler could not have relied on opulent festivals or fed large labor forces needed to build impressive monuments. Consequently, going to war more often would have been an effective tactic to maintain status, prestige, and power. Eventually, the growth in conflict became explosive.
The researchers believe the findings have implications for the debate about contemporary climate change. Concern is growing that climate change effects would increase violence within and between human societies.The Intergovernmental Panel on Climate Change has cautioned that climate change will exacerbate conflict at a range of scales, from inter-personal violence to civil war, while the US Department of Defense has classified climate change as a threat multiplier, suggesting that it could lead to political and social unrest and increased terrorism.  “
Further Information
Increasing temperature exacerbated Classic Maya conflict over the long term
Climate Change Incited Wars Among the Classic Maya