Last week, the ratio of carbon dioxide in the atmosphere soared to the highest daily average ever recorded by an air monitor station at Mauna Loa in Hawaii—nearly 400 parts per million (ppm), said John Ewald, a spokesman for the National Oceanic and Atmospheric Association, who called it "an extremely important milestone." When that gauge was installed in 1958, the observatory measured a CO2 concentration of 313 ppm. The number means there were 313 molecules of carbon dioxide in the air for every 1 million molecules of air.
"That warmer and more moist air (caused by the CO2) creates the conditions that certain pathogens thrive on," Lawrence said. "That's the dilemma with things like the coffee fungi and some of the problems with citrus."
The world's collective appetite also is growing as populations rise, leading large, commercial growers and exporters to ship more food internationally—and allowing certain plant-consuming bacteria, fungi and viruses to "hitchhike half way around the world in a day," Lawrence added.
Moreover, to help meet the need to feed those extra mouths, industrial agriculture has increasingly turned to "mono-culture" farming to boost harvests. That means using science to alter plants and sewing huge fields—fencepost to fencepost—with single crops.
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"For instance, corn plants in the American Midwest are grown closer together and taller than they have been in the past because we're genetically engineering them to do that," said Lee Hannah, senior fellow at Conservation International, a global nonprofit that advocates for sustainable policies. "That produces a lot more food. But it also makes that corn more vulnerable to disease, which, if it gets into that mono-culture system, can sweep through it much as a disease will go through a city a lot faster than it does a rural countryside.
"We're in a situation where the food supply is more vulnerable than it has ever been," added Hannah, also an adjunct faculty member at the Bren School of Environmental Science & Management at the University of California at Santa Barbara.
Hannah authored a recent study that predicted climate change may shrink California's wine-growing areas by as much as 70 percent by 2050.
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But less wine in our homes could—some conservationists hope—grab the attention of American consumers who can't otherwise get their heads around shrinking polar ice caps.
"Maybe seeing this impact all this has on our ability to raise the food we depend on will get us to the tipping point of real policy change and real action," Lawrence said. "I hope so."
—By Bill Briggs, NBC News contributor