Scientists from the University of California, Berkeley and Princeton University discovered a strong link between shifts in climate to human violence around the world. The study found that even minor climate deviations, such as slight changes in normal temperature and rainfall, can greatly increase the risk of conflict.
The link between climate variations and violent behavior was noted on a small scale—in one-on-one crimes like assault, murder or domestic abuse—as well as on a much grander scale involving riots or civil war.
Unlike previous similar studies, this project combined data and evidence from a wider number of fields such as economics, political science, geography, psychology and archeology, according to Professor Edward Miguel from the University of California Berkeley.
Climate shifts researchers explored included temperature as well as rainfall—from very low rainfall and drought conditions to extreme amounts of rainfall.
The researchers compared extensive data, spanning from ancient times until today. Collecting more material than any prior study, the researchers were able to show that the Earth’s climate plays a more influential role in human affairs than previously thought.
Among the historical correlations researchers found was the case of the advanced Mayan civilization which was established around 2000 BC in what is now Mexico and Central America. Some scholars say this Mesoamerican civilization peaked between the years 250 to 900 AD, when it mysteriously collapsed.
Scientists and historians, including those involved in this study, theorize that climate may have had a lot to do with the Mayan decline and failure.
“The Mayan civilization, the Mayan empire…during the 9th century AD, experienced an unprecedented century of warm, dry weather,” said Miguel. “In fact, they had three mega-droughts during that century and at the end of the third mega-drought, that’s the time at which that civilization collapsed into civil war never to recover its previous grandeur.”
“When you have temperature spikes on top of what’s already a very hot place, that’s associated with political violence in Somalia, so Somalia is an African case where you can see this come through very clearly,” said Miguel.
The study also found a link between high temperatures and a rise in domestic violence in India.
In Brazil, scientists found a correlation between rainfall and land invasions. Miguel pointed to a landless people’s movement in the South American country that organizes violent raids.
“It turns out that when rainfall is really bad, either way too much or way too little rainfall in a given year, in those years you see spikes in the number of land invasions in Brazil,” said Miguel.
Results of the Berkeley/Princeton research could be used to predict future violent trends and potential trouble spots around the world, which could help in the development of strategies that would address possible violence and conflict in the future.