Climate change could be to blame for many of the wars in China during the past millennium, says an article published recently in Human Ecology. The study, the first quantitative examination of the link between conflict and temperature changes, is a milestone in climate change research.

David Zhang and co-authors compared the 899 wars that occurred in eastern China between A.D. 1000 and 1911 with climatic data for the same period. They found that warfare frequency in eastern China—particularly in that region’s southern part—correlated strongly with temperature oscillations. Warfare ratios in the cold phases were twice as high as in the warm phases. Furthermore, almost all dynastic changes and warfare peaks coincided with cold phases.

“In general, rebellion was the dominant category of war,” write the authors. “The rebellions were predominantly peasant uprisings induced by famine and heavy taxation, since farmers were always the first to suffer from declining agricultural production.”

The authors surmise that by affecting agriculture, cooler temperatures disrupted food supply, especially in the ecologically vulnerable northern part of eastern China. Food scarcity could have triggered rebellions or forced people to migrate, further exacerbating food shortages in certain areas. Migration could also have generated tension between groups, producing local conflicts—especially when China was populated by nomadic tribes that could move freely. The authors also hypothesize that food scarcity may have encouraged opposing Chinese armies to conduct cross-border raids on each other’s crops. However, additional, more detailed analysis of the pathways leading from cooler temperatures to conflict in eastern China is needed.

It is unclear whether the correlation observed by Zhang in eastern China will hold true for other parts of the world. We should also be careful not to use this one study to draw premature connections to today’s unprecedented climate change. However, we hope additional quantitative studies will be carried out; they would be solid contributions to the research on climate and security, which currently suffers from a scarcity of empirical data.

Last week, policymakers, business leaders, and farmers gathered in Oslo at the second annual African Green Revolution Conference to discuss ways to increase agricultural productivity in Africa. The conference, inspired by former UN Secretary-General Kofi Annan’s July 2004 call to revolutionize African farming, and co-sponsored by two Norwegian public development organizations and two transnational companies, focused on how partnerships between the public and private sectors can offer valuable opportunities for agricultural development. Pedro Sanchez of Columbia University’s Earth Institute cited Malawi, which last year managed to turn a 40 percent grain deficit into a 25 percent surplus, as the first successful African Green Revolution country. Yet other attendees warned that this growth had been achieved partially at the expense of environmental degradation—particularly deforestation—and urged agricultural development programs in Africa to strive for growth that will be sustainable in the long-term.

Also last week: Representatives from 158 countries met in Vienna for a weeklong UN conference on reducing greenhouse gas emissions. The delegates agreed that industrialized nations should aim for a non-binding target of reducing their emissions by between 25 and 40 percent of 1990 levels by 2020. This goal is expected to serve as a loose framework for the major UN-sponsored international climate talks that will be held in Bali, Indonesia this December. At the conference, China rejected criticism that it has not been doing enough to combat climate change, arguing that its one-child policy, by preventing 300 million births over the past three decades, has also kept the country’s levels of greenhouse gas emissions significantly lower than they would have otherwise been.

They say that a good man is hard to find. But in some countries, the opposite is true: a good woman is hard to find—because it’s hard to find women at all. According to a recent article by the BBC, the Chinese city of Lianyungang has eight men for every five women. Ninety-nine cities in China have gender ratios as high as 125 (125 men for every 100 women, or a 5:4 ratio).

But China is not alone. India has a gender ratio of 113, and the ratio in Asia as a whole is 104.4. In the United States, by contrast, the rate is 97, meaning that there are more women than men.

Gender imbalances are caused by cultural and economic preferences for male children, which contribute to sex-selective abortion and female infanticide. Over 60 million girls are “missing” in Asia as a result of these practices.

Furthermore, some government policies may intensify these gender preferences. China’s one-child policy, for example, may cause concern among parents, particularly in rural areas, that having a female child endangers their family’s future. Government policies intended to combat skewed gender ratios, such as bans on prenatal ultrasounds for the purpose of determining the baby’s sex and bans on sex-selective abortion, have proven ineffective.

Unbalanced gender ratios have consequences that reach beyond just the mothers and children involved. According to Valerie Hudson, high gender ratios leave many men without prospects for marriage, which may mean these men have fewer incentives to contribute peacefully to society. The men with the slimmest prospects for marriage are likely to be unemployed, poor, and uneducated, so they are already at increased risk for violent behavior. Hudson cites statistical evidence showing links between high gender ratios and higher rates of violent crime, drug use, trafficking, and prostitution.

Hudson and co-author Andrea den Boer cover these links in greater detail in their book Bare Branches: The Security Implications of Asia’s Surplus Male Population. In the 11th issue of the Environmental Change and Security Report, Richard Cincotta takes issue with some of the statistical methods that Hudson and den Boer use. He argues that what is important is not nationwide gender ratios, but the number of “marriage-age men” (25-29 years old) and “marriage-age women” (20-24).

While there may be some debate over whether the relationship between gender ratios and violent behavior is a causal one, there is little doubt about what causes the gender imbalances in the first place. An end to preferences for female children will be beneficial not only to girls and women, but to societies as a whole.

Photo Credit: A subway in China, courtesy of flickr user 俊玮 戴.

As the Cold War came to an end in the late 1980s and early 1990s, the U.S. and Soviet (then Russian) militaries conducted joint scientific assessment of radioactive threats in the highly militarized waters off Russia’s Northwest. The Norwegians started the dialogue with Gorbachev’s USSR a few years earlier and helped bring in the Americans as relations began to thaw. Environmental threats were an honest concern: Norwegians worried for example about irradiating their lucrative salmon industry and the Russian habit of decommissioning their nuclear submarines by just scuttling them with reactors intact worried everyone.