Every year, in a tradition dating to the 1940s, thousands gather in the Spanish town of Buñol for La Tomatina, a giant “food fight,” in which participants gleefully pelt each other with tomatoes and get very, very messy. There’s blood in the streets, but it belongs to the tomatoes. However, according to a study in the prestigious journal, Science, and two in the Proceedings of the National Academy of Sciences (PNAS), we are about to experience food fights of a very different, more deadly type.

One group of researchers examined the historic links between climate change and incidents of war in Europe and Asia. Going back a millennium, they uncovered a “strikingly high” correlation between temperature variation and the number of wars. Their explanation? Climate change has “significant direct effects on land-carrying capacity” which in turn “affects the food supply per capita.” In their words, “the paths to those disasters operated through a reduction in agricultural production.”

As one might guess, these researchers, working from institutions in China, the U.S., and U.K., found that the highest correlation between climate change and war occurred in arid regions, precisely the areas where food supplies were must vulnerable to climatic perturbations.

Another group of researchers, based at Berkeley, NYU, Harvard and Stanford, focused on Africa. They too found “strong historical linkages between civil war and temperature…with warmer years leading to significant increases in the likelihood of war.” What might we then expect to happen in Africa in the future? The researchers point out that, “When combined with climate model projections of future temperature trends, this historical response to temperature suggests a roughly 54% increase in armed conflict incidence by 2030, or an additional 393,000 battle deaths if future wars are as deadly as recent wars.”

Bear in mind that projected temperature increases for 2030 are a fraction of those predicted later in the century. One shudders to think how global peace and security will be affected then. The point has not been lost on military leaders.

In 2007, as food riots erupted in the state of West Bengal in India and over tortilla prices in Mexico, 11 retired US three and four-star admirals and generals, including General Anthony Zinni, former Commander-in-Chief of the U.S. Central Command, issued a report warning that climate change will be a “threat multiplier for instability in some of the most volatile regions of the world” and that it would “add to tensions even in stable regions….” In Africa these military leaders foresee climate change being an “incubator of civil strife, genocide and the growth of terrorism.” In the Middle East, they state “the potential for escalating tensions, economic disruption, and armed conflict is great.” And they believe that Asia “could be among the hardest hit regions.”

Climate change causes agricultural problems that in turn give rise to hardship, hunger, unrest, and even war. Not a pretty picture. In this context it is hardly surprising that the CIA is establishing a new Center for the Study of Climate Change, or that the Pentagon now includes climate change among the security threats it assesses in its quadrennial defense reviews.

We need not rely solely on statistical correlations in academic papers to demonstrate the link between food and political insecurity. Just look back at 2007-8, when the price of rice surged 200 percent and wheat and maize rose by more than 100 percent. Across the world, riots erupted and at least one government fell as a result. This year food prices have returned to record levels. The government of Tunisia has fallen, and Egypt is on the brink. In both cases, discontent over food issues has been part of the mix.

Now, two U.K. government departments are warning that global warming may cut India’s farm output by a quarter. Similar decreases in production of major staples have been predicted for Africa in the pages of the journal Science.

Clearly climate change and security are fused together by the impact of climate change on food production. It is this link that will undermine global peace and security in the future. So, as General Zinni notes, we can act now, or “we will pay the price later in military terms. And that will involve human lives. There will be a human toll.”

In other words, it should be a military priority to prepare agriculture for climate change. Yet this is only starting to register even as a development priority. Country after country and crop after crop, farmers will need new varieties in the field that are adapted to the higher temperatures and to the new pests and diseases that will follow in their wake.

New varieties are not possible without access to crop diversity. So if past is prologue, we need to be coming to grips with the fact that conserving the crop diversity necessary for increasing food production, particularly in a climate changing world, is a national security issue for all countries.

In essence, General Zinni and his colleagues are saying that converting at least some swords into ploughshares to avoid future conflict makes good military sense.

The good news is that this is a rare military expense that can be shared between all nations. Less than a half of one percent of the increase in global military spending between 2008 and 2009 would be sufficient to ensure the conservation and availability of crop diversity forever! Invested in an endowment it would generate sufficient income to maintain our most potent weapon in the fight to adapt agriculture to climate change-crop diversity.

Think of it this way: Failure to sever the link between climate change and war represents a breach of security and a threat to peace. Failure to take easy steps to adapt agriculture to climate change is a failure to react to an avoidable threat. Strategically, and morally, unforgivable. An unmistakable message is coming from our early warning systems. If we ever intend to stop food fights, we’ll have to conserve crop diversity, not just throw it at each other.