“We had originally thought that it all came down to starvation, but after talking with Maya specialists, we decided that wasn't convincing,” Collard said.
He explained that maize would have been difficult to transport, in which case the idea of attacking neighbors for food did not seem very likely.
“Instead, it's probably better to consider the increase in warfare in a way that we often think about warfare today — namely as a tool for the elite to maintain support,” Collard said.
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.
“I think of it as being similar to the way that some modern political leaders seem to use conflict with neighbors to distract from problems within their country,” Collard said.
Eventually, the growth in conflict became explosive.
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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.
“Our study shows that small year-to-year changes in climate can result in large, negative effects over the long term,” Collard said. “This is a problem for us, humans, because most of us are oriented towards the short term.”
“We run the risk of ignoring changes that will affect our children and grandchildren, because we can't perceive those changes,” he added.
Some very important questions still need to be investigated.
“Most obviously, we need to know whether the effect is a regional one, specific to the Maya area, or one that holds for other parts of the world,” Collard said.
But he warned that without government support it won’t be possible to answer this and other crucial questions.
“The data we used in the study were collected by researchers funded by US agencies that have been targeted for massive cuts by President Trump and his administration,” he noted, pointing to the impact of politics on his research. “I think most people — most voters — want evidence-based government policies, and we can't have evidence-based policies without evidence.”