Friday, July 1, 2022

Drought might not be the driver behind disruption of Maya society

Maya had many highly drought resistant edible plants available to them.

Various studies suggested that the disruption of Classic Maya society in the Yucatan Peninsula of southeastern Mexico and northern Central America at the end of the ninth century coincided with extended droughts.

Although climate change cannot fully account for the multifaceted, political turmoil of the period, it is clear that droughts of strong magnitude could have limited food availability, potentially causing famine, migration, and societal decline. Maize was undoubtedly an important staple food of the ancient Maya, but a complete analysis of other food resources that would have been available during drought remains unresolved.

A new analysis by UC Riverside archaeologist Scott Fedick and plant physiologist Louis Santiago shows the Maya had nearly 500 edible plants available to them, many of which are highly drought resistant. This study casts doubt on drought as the driver of ancient Mayan civilization collapsed. 

Study analysis has now been published in the Proceedings of the National Academy of Sciences.

“One of the keys for understanding the potential for drought to have destabilized ancient Maya society is whether the documented meteorological droughts led to agricultural drought and were severe enough to disrupt food production and cause food shortages. Meteorological drought refers to rainfall amounts, while agricultural drought is related to the availability of water for crops; specifically, water availability for a particular crop to grow at a particular time and place. Archaeologists have tended to equate agricultural drought directly with meteorological drought, with the assumption there is a direct causal/proportional relationship between rainfall deficit and agricultural drought.” Study quotes.

In this study, researchers considered three levels of drought severity:

  • Short-duration drought, a year with the dry season extended in duration for up to an additional 3 mo.
  • Moderate-duration drought, up to a full year of dry season rainfall pattern, essentially missing a rainy season.
  • Extreme drought, multiple years without normal rainfall, basically a year-to-year pattern of only dry season precipitation.

“Even in the most extreme drought situation — and we have no clear evidence the most extreme situation ever occurred — 59 species of edible plants would still have persisted,” Santiago said.

Cassava, a drought-resistant edible plant grown by the ancient Maya. Credit: Thamizhpparithi Maari
Cassava, a drought-resistant edible plant grown by the ancient Maya. Credit: Thamizhpparithi Maari

Some of the toughest plants the Maya would have turned to include cassava with its edible tubers and hearts of palm. Another is chaya, a shrub domesticated by the Maya and eaten today by their descendants. Its leaves are high in protein, iron, potassium, and calcium.

“Chaya and cassava together would have provided a huge amount of carbohydrates and protein,” Santiago said. 

Unable to find a master list of indigenous Maya food plants, Fedick recently compiled and published one that draws on decades of Maya plant knowledge. Faced with much speculation about drought as the cause of Maya social disruptions, he and Santiago decided to examine all 497 plants on the list for drought tolerance. 

“When botanists study drought resistance, they’re usually talking about a specific plant, or a particular ecosystem,” Fedick said. “One of the reasons this project was so challenging is because we examined the dietary flora of an entire civilization — annuals, perennials, herbs, trees, domesticates, and wild species. It was a unique endeavor.”

Though the researchers do not have a clear answer about why ancient Maya society unraveled, they suspect social and economic upheaval played a role. 

“One thing we do know is the overly simplistic explanation of drought leading to agricultural collapse is probably not true,” Fedick said. 

The research also demonstrates the importance of exploiting a variety of plants to survive drought and climate change

“Even given a series of droughts, maintaining a diversity of resilient crops would enable people, both ancient and modern, to adapt and survive,” Santiago said.

“Our analysis indicates availability of 83% of food plant species in short-term drought, but this percentage drops to 22% of food plant species available in moderate drought up to 1 y. During extreme drought, lasting several years, our analysis indicates availability of 11% of food plant species. Our results demonstrate a greater diversity of food sources beyond maize that would have been available to the Maya during climate disruption of the Terminal Classic period than has been previously acknowledged. While drought would have necessitated shifts in dietary patterns, the range of physiological drought responses for the available food plants would have allowed a continuing food supply under all but the most dire conditions.” Study quotes.

Journal Referene

  1. Scott L. Fedick and Louis S. Santiago – Large variation in availability of Maya food plant sources during ancient droughts. PNAS January 4, 2022 119 (1) e2115657118; DOI: 10.1073/pnas.2115657118
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