posted: 21 November 2007 12:50 pm ET
History may be bound to repeat itself as Earth’s climate continues to warm, with changing temperatures causing food shortages that lead to wars and population declines, according to a new study that builds on earlier work.
The previous study, by David Zhang of the University of Hong Kong, found that swings in temperature were correlated with times of war in Eastern China between 1000 and 1911. Zhang's newer work, detailed in the Nov. 19 online edition of the journal Proceedings of the National Academy of Sciences, broadens its outlook to climate and war records worldwide and also found a correlation between the two.
"This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles," Zhang said.
The research does not represent direct cause-and-effect, but rather suggests a link between climate and conflict.
Looking to the past
Because water supplies, growing seasons and land fertility can be affected by changes in climate, they might prompt food shortages that could in turn lead to conflicts, such as local uprisings, government destabilization and invasions from neighboring regions, the researchers speculate. These conflicts and the food shortages that cause them could both contribute to population declines, they add.
To see whether changes in climate affected the number of wars fought in the past, the researchers examined the time period between 1400 and 1900, when global average temperatures reached extreme lows around 1450, 1640 and 1820, with slightly warmer periods in between.
Using records reflected in tree rings and ice cores, the researchers compared temperature changes to a database of 4,500 wars worldwide that co-author Peter Brecke of Georgia Tech compiled with funding from the U.S. Institute of Peace.
The results of the comparison showed a cyclic pattern of turbulent periods when temperatures were low, followed by more tranquil times when temperatures were higher.
This correlation doesn't necessarily mean that all-out war is imminent, William Easterling of Pennsylvania State University, who was not affiliated with the work, had said in regards to Zhang's earlier work. However, the changing distribution of resources could certainly increase international tensions, he added.
The new study also showed population declines following each war peak. Specifically, during the frigid 17th century, Europe and Asia experienced more wars of great magnitude and population declines than in more temperate times.
Projecting into the future
To connect temperature changes of less than 1 degree Celsius (1.8 degrees Fahrenheit) to food shortages, the authors used price increases as a measure of decreases in agricultural production and found that when grain prices reached a certain level, wars erupted.
Though these historical periods of climate change featured cooler temperatures, current rising global temperatures could still cause ecological stress that damages agricultural production.
"Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source," Brecke said.
"The warmer temperatures are probably good for a while, but beyond some level, plants will be stressed," Brecke explained. "With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone, and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water."
Climate War Threatens Millions
More than 100 countries face political chaos and mass migration in global warming catastrophe
A total of 46 nations and 2.7 billion people are now at high risk of being overwhelmed by armed conflict and war because of climate change. A further 56 countries face political destabilisation, affecting another 1.2 billion individuals.
This stark warning will be outlined by the peace group International Alert in a report, A Climate of Conflict, this week. Much of Africa, Asia and South America will suffer outbreaks of war and social disruption as climate change erodes land, raises seas, melts glaciers and increases storms, it concludes. Even Europe is at risk.
'Climate change will compound the propensity for violent conflict, which in turn will leave communities poorer and less able to cope with the consequences of climate change,' the report states.
The worst threats involve nations lacking resources and stability to deal with global warming, added the agency's secretary-general, Dan Smith. 'Holland will be affected by rising sea levels, but no one expects war or strife,' he told The Observer. 'It has the resources and political structure to act effectively. But other countries that suffer loss of land and water and be buffeted by increasingly fierce storms will have no effective government to ensure corrective measures are taken. People will form defensive groups and battles will break out.'
Consider Peru, said Smith. Its fresh water comes mostly from glacier meltwater. But by 2015 nearly all Peru's glaciers will have been removed by global warming and its 27 million people will nearly all lack fresh water. If Peru took action now, it could offset the impending crisis, he added. But the country has little experience of effective democracy, suffers occasional outbreaks of insurgency, and has border disputes with Chile and Ecuador. The result is likely to be 'chaos, conflict and mass migration'.
A different situation affects Bangladesh. Here climate-linked migration is already triggering violent conflict, says International Alert. Droughts in summer combined with worsening flooding in coastal zones, triggered by increasingly severe cyclones, are destroying farmland. Millions have already migrated to India, causing increasingly serious conflicts that are destined to worsen.
In Africa, rivers such as the Niger and Monu are key freshwater resources passing through many nations. As droughts worsen and more water is extracted from them conflicts will be inevitable.
In Europe, most countries are currently considered stable enough to cope with global warming, apart from the Balkans; wars have left countries such as Serbia and Montenegro politically weakened. As temperatures rise and farmland is reduced, population pressures will trigger violence that authorities will be unable to contain.
Some nations on the risk map, such as Russia, may cause surprise. 'Moscow's control of Russia as a whole will not be undermined by global warming,' said Smith. 'But loss of farmland in some regions will lead to local rebellions like those already triggered in Chechnya.'
Conflict triggered by climate change is not a vague threat for coming years, he added. 'It is already upon us.'
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