Thanks to fossil records and measurements taken for decades at Mauna Loa, Hawaii, scientists know that our atmosphere contained less than 320 parts per million (ppm) of CO2 in 1960, but contains 396 ppm today. Scientists also know that atmospheric CO2 now exceeds the A1F1 scenario (essentially ‘business as usual’) for climate change from the International Panel on Climate Change. Thousands of scientists from around the globe contribute to this international body, established by the United Nations and World Meteorological Organization.

Why should you care?

Lewis Ziska, a plant physiologist with the Department of Agriculture’s Agricultural Research Service, points out that climate change affects plants. Plants make up some 90 percent of biomass on the earth — about 300,000 species and counting — but only around 15 of them provide most of our food. Plants need nutrients, water, sunlight and a carbon source to convert light into energy, so any changes in CO2 will affect plant growth.

The world runs on cereal: Wheat, corn and rice represent 50 percent of the calories consumed worldwide. In the 1940s, Norman Borlaug of the International Maize and Wheat Research Center in Mexico led what is now know as the Green Revolution, breeding new strains of wheat and other crops that had significantly higher yields.

The Green Revolution, Ziska says, enabled our modern agriculture industry to support about four billion of the earth’s soon-to-be seven billion people that it otherwise would not have been able to. But population growth has now bypassed the abilities of even the Green Revolution, and we’re facing a “gathering storm” of increased demand for meat and biofuels and no more arable land.

The Green Revolution depended on clean, available water; energy to make fertilizer; and a stable climate, because the modified crops are monocultures, and genetically identical. Climate change will affect all of these — water, energy, weather — as well as, indirectly, pests and weeds, and ultimately, the quality and safety of our food.

Creating fertilizer is extremely energy intensive — modern corn requires about 150 to 200 pounds per acre of nitrogen, so using corn to make fuel will require huge reserves of natural gas. Globally, about 75 percent of our freshwater is used for irrigation today.

The most commonly grown grains, which require a lot of that water and have little genetic diversity, were developed for optimal growth in an environment that no longer exists, Ziska points out. The more wild, variable lines of plants are going to handle increasing atmospheric CO2 much better than our crops will.

Take rice, for example. The world’s poor rely on rice for the bulk of their calories, Ziska says. He led a recent study that found rising levels of CO2 facilitated the flow of genes from wild or “weedy” varieties of rice to domesticated ones. This could mean that domesticated varieties — the genetically altered, herbicide resistant cultivated varieties supplying those calories — could take on characteristics of wild varieties that are considered undesirable in crop plants, such as more height variation and greater flower production.

At higher concentrations of CO2, hybrids between the weedy and domesticated plants contained more genes from the weedy parent than at lower concentrations. In other words, high CO2 levels facilitated more flow of genes from weedy to domesticated than the other way around. This was the first study to demonstrate that increasing CO2 influences gene flow between closely related plants, and that the flow is not the same in both directions.

What does that mean? Rising CO2 is likely to mean less nutritious crops and lower yields. Farmers will have to change the way they operate, and plant breeders will need to consider the effects of climate change moving forward.

One change that will work, Ziska says, is smaller, more diverse farms — in other words, the way things used to be. Growing a high number of varieties on one plot means that no matter what happens, you’ll get some food.

The practice of polyculture — for example, raising cattle to produce fertilizer for crops on the same farm — could help. So could improved infrastructure, such as more efficient water capture, and technology, things like a smart phone app that enables farmers to better time application of nitrogen. At any rate, our current agriculture model is not sustainable.

“To my knowledge, there’s never been a GMO line that produced more than a traditionally-developed line,” Ziska says. He points out that the end-goal of private-sector research on crop varieties is to sell a product. Meanwhile, about 3/100 of one percent of the U.S. budget goes to agriculture research, and a federal program to study climate change was discontinued.

This is ironic, given that every year, hunger kills more people than AIDS, malaria and TB combined. Simply put, food security equals national security, Ziska asserts.

“I wish folks could see the connection between global food security and national security. But the disparity between rich countries where food is in over-supply and obesity is a problem, and poorer countries where people travel the countryside for scraps is one that doesn’t resonate. I suspect that if you ever go hungry, particularly as a child, you never forget it. A full bowl of rice does more against terrorism than all our missiles.”