Cats got claws

There’s been a lot of debate surrounding the cause of the Mayan collapse. Within this debate, there is even more disagreement on the timing and duration of a drought event.

In this post I want to outline the 'mega-drought' hypothesis and demonstrate how the importance of this theory has changed over time.

In 1995 Hodell et al presented data from a sediment core taken from Lake Chichancanab, on the Yucatan Peninsula. This evidence suggested that a ‘mega-drought’, which lasted over 200 years, was the cause of the Mayan collapse.

Site of Lake Chichancanab. Source: GoogleMaps

This theory has been extensively criticised due to the questionable evidence used to support it. Hodell et al (2005) defended their earlier work, asserting that their analysis had been misinterpreted. Hodell (2005) discusses evidence of a 50-year and 208-year drought cycle which corresponded with the decline of the Maya. Although elements of their argument correlate with other academics’, such as high climatic variability, fundamental differences remain especially the occurrence of a drought cycle for these periods of time.

Carleton et al (2014) is heavily critical of Hodell’s 50-year and 208-year drought cycles. Carelton re-evaluated the empirical data from Hodell (1995 and 2005) and rather bluntly asserts that “there is no evidence for a 208-year drought cycle in the Lake Chichancanab dataset” or in fact evidence from this core of any drought. They continue to argue that these 2 drought cycles came about by biased interpolation and that the ‘evidence’ is a methodological artefact. 

An image of a real Mayan artefact. Source: Royal Ontario Museum

However this evaluation may have been a bit harsh. Frappier et al (2014) argues that the magnitude of mega-droughts during the Mayan period were underestimated. New evidence from mud layers in stalagmites from caves in the Yucatan Peninsula provide annually resolved proxy evidence that suggests mega-droughts played an important role in the Mayan collapse. They also understand the complexity of factors that led to collapse, suggesting that droughts caused wildfires, brought about pest outbreaks and that a high frequency of droughts over a short temporal scale would have caused shifts to alternate stable states. A combination of these forcing factors may well have been too much for the Mayans to handle.

Hopefully this shows that there's a lot of debate over the role climate played in the Mayan collapse, especially with the emergence of more and more accurate techniques.

Next time I'll look a bit more into drought and afterwards move on to the next case study!