Archaeologists study how pre-existing vulnerabilities link to climate shock

Margaret Nelson, one of four ASU archaeologists are looking into how pre-existing vulnerabilities amplify the affects of climate shock as part of an international team examining how people can be most resilient to climate change when it comes to food security. (Photo by Ryan Liu) Margaret Nelson, one of four ASU archaeologists are looking into how pre-existing vulnerabilities amplify the affects of climate shock as part of an international team examining how people can be most resilient to climate change when it comes to food security. (Photo by Ryan Liu)

Climate shocks and natural disasters have proven to be devastating to nations throughout history, but what role do pre-existing vulnerabilities like food shortage play in amplifying the impact of climate shock?

Four archaeologists from ASU are part of an international team to answer that question.

Dean Margaret Nelson is part of the team. She said the international team is made up of archaeologists, historians, climate experts and geographers who are all interested in the relationship between human societies and culture change.

“That’s what brought us together,” she said.

The other University archaeologists involved in the study are professors Keith Kintigh, Michelle Hegmon and Kate Spielmann, who are all part of the School of Human Evolution and Social Change.

Nelson said they spent three years working together and defining important issues that could be addressed with historical and archaeological information. She presented her findings to the American Association for Science.

In order to obtain the data needed for the study, the team had to do a lot of fieldwork. They then analyzed animal bones, seed remains around archaeological sites, pottery and metal and glass objects

“A shock is not exactly the same as a change in climate,” she said. “Shock is something that is completely unexpected and outside of human experience.”

Nelson said the recent upturn in global temperature would not be an example of climate shock.

“That’s not a shock, even though it is a change,” she said. "It’s happening gradually so each year we have the experience of increase carried to the next year where it may, if we were to look 50 years from now, think that it’s a huge change.”

Hurricane Sandy would be an example of climate shock.

“New York City had never experienced anything like that before,” said Nelson. “Some of the very serious droughts that have happened in India have to do with climate shock as well.”

Nutrition freshman Maureen Philzone is a Long Island native and had first-hand experience with Sandy.

"We were not prepared at all," she said. "I want to say we are more prepared than last year, because we know better now."

Nelson’s team conducted its research in the southwestern U.S. and took all of the records of rainfall in the last thousand years. They have records of precipitation that go back over a thousand years.

“The question is, ‘Are there years where people experience such a dry period for so many years that they have never experienced anything like this?'" she said. "That’s a climate shock. A shock isn’t only how bad it is, but how long it lasts.”

Specialists can diagram tree rings and find out when the rainfall was high.

“Each ring width is wider along the line if there is more water and skinnier if there is less weather,” she said. “We used a period of 600 years for this study.”

The team has also been collaborating with researchers in the North Atlantic. They have been analyzing people who faced a set of challenges with extreme cold, iciness and storminess. The team used archaeological records as well as historical records.

“We can look back in the past and know what these shocks were,” she said. “(We can find out) what the relationship (is) between how vulnerable to food shortage people are before a shock and how they are affected by the shock.”

Another question researchers raised is how natural is a disaster—in other words, they examined how much human actions contribute to natural disasters.

“I, for example, could be very vulnerable to being hungry if I make a low income or no income at all,” Nelson said. “It’s not that I’m actually hungry; it’s that I could be hungry if something comes along to jar my situation.”

Nelson said there are factors that make people more vulnerable. Food diversity is one of those factors.

“If your food supply is based on very narrow things, almost anything can tip that,” she said. “Not having enough food storage can also make you fall short.”

Archaeology professor Michelle Hegmon was one of the archaeologists on the team. She primarily worked in the Mimbres region of the southwest.

The Mimbres were a branch of the Mogollon culture that was localized in southeastern Arizona and southwestern New Mexico around 1000 AD.

She said vulnerability to food shortages is not usually caused by an actual shortage of food, but rather by social or organizational factors that limit people's abilities to cope with difficult times.

“In the Mimbres region of southwest New Mexico, we observed this process when people, during good times, not unlike the stock market bubble, expanded their settlements into marginal areas that could only be farmed when there was above-average rainfall," she said.

Hegmon said when the climate returned to normal and below normal precipitation, they could no longer live in those areas.

“This may have been part of what precipitated a big move out of the Mimbres Valley at the end of the Mimbres Classic period,” she said. “As far as we know, no one starved, but the change was probably difficult and disruptive.”

Not having strong social relationships can impact liability.

“If you wall yourself off then you have less recourses if something bad happens,” Nelson said.

Nelson said there is such a consistent relationship between climate shock and vulnerability that it can’t be ignored.

“There is very little effort to reduce or prevent vulnerabilities,” she said. "Had these vulnerabilities not existed in the first place, some of these 'natural disasters' wouldn’t have even existed in the first place.”

Reach the reporter at or follow her on twitter @kelciegrega

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