The US Department of Agriculture’s crop zone map is a must-have for farmers and gardeners. The color-coded map divides the United States into 26 different zones split by five-degree increments based on the coldest temperatures of the year. The map, which often accompanies seed packets and plant catalogs, helps gardeners know what they can and cannot plant.
In January, the zones changed. For the first time since 1990, the USDA revised the map to take into account shifting temperatures. Eighteen cities are in newer, warmer zones. Entire states now come in a different mix of colors. Compare the 1990 and 2012 maps and it looks as if much of the United States has moved southward.
From vital necessities like rice to indulgences such as wine, many foods will have a harder time making it to market as climate change becomes more intense.
Potatoes Because they thrive only in a very narrow temperature window, potatoes are highly susceptible to global warming. Farmers might be able to manage by shifting their potato plots to higher altitudes or planting at different times of the year, but the dislocations still threaten to be serious. Researchers figure that harvests could decline anywhere from 9 to 32 percent, depending upon how farmers adapt. That’s bad news, given that potatoes are the fourth most important crop after rice, wheat, and corn. Higher temperatures could also worsen outbreaks of “late blight” – the potato disease that caused the Irish Famine in the 1840s.
Maple syrup The flow of a maple tree’s sweet sap is controlled by alternating freezing and thawing in late winter. Already, higher temperatures are impacting syrup harvests. Researchers say that by the end of this century the southern reaches of sugar maple habitat, like Pennsylvania, may no longer be able to sustain production.
Rice Scientists have found that yields in some rice-producing countries have dropped 10 percent as nighttime temperatures have increased. Another threat: rising waters. A three-feet increase in global sea level would flood hundreds of thousands of square miles of coastal wetlands that are among the most productive rice-growing areas of the world.
Wine Terroir is the crucial ingredient when it comes to wine making. A French word (of course) terroir stands for the unique characteristics of geology, climate, and geography that produce a specific grape and create a unique wine. When climate changes, so will the grapes of a particular region, along with its wines. In the next 30 years, according to a Stanford University study, the number of high value vineyards in California could shrink by half.
The new map confirms what millions of American gardeners already know: Temperatures are rising, rainfall is getting weirder, and plants are responding.
Farmers and gardeners worldwide are noticing that the weather ain’t what it used to be. Last year, massive monsoons and multiple typhoons reduced rice harvests across Southeast Asia. Lengthy droughts in recent years have impacted wheat growers in Australia and Argentina. Coffee producers, potato growers, winemakers, even maple syrup tappers – all are worried about the consequences of global warming.
The weather, of course, has never been exactly dependable. Farmers have always been at the mercy of the sun and the rain. But general weather patterns have at least been predictable, informing farmers when to sow their seed and when to harvest. As those patterns become less reliable, growers will be tested to come up with new agricultural rhythms or plant crops they’ve never grown before.
The new stresses on agriculture might be tolerable if it weren’t for the fact that the human population keeps growing. The strains are worsening between the daily caloric demands of 7 billion people and how much food farmers can supply. As declining water tables, soil erosion, droughts, and floods depress crop yields, there are more mouths to feed than ever before. The global food system doesn’t have much wiggle room for failure. Commodity markets are already feeling the pinch: Global food prices hit an all-time high in 2008 and, after a dip, broke records again in 2011.
Climate change’s likely impact on agriculture represents the greatest threat posed by global warming. We can move our cities inland if the seas rise. Most of us will find some way to stay cool as the summers get worse. But a couple of major crop failures would be a much different story. “We are one bad harvest away from global chaos,” Lester Brown of the Earth Policy Institute has warned.
The glib and the cynical like to joke that a warmer planet will offer some new agricultural benefits. Sure, it might be fun to think about growing figs in Boston or avocados near Seattle. We might gain some new growing regions toward the poles even if we lose others closer to the equator. But the scales won’t balance out so evenly – just ask the Russian wheat farmers who lost nearly half of their 2010 crop to unprecedented drought and fire.
Unless we act immediately to plug our industrial emissions (and perhaps even if we do), we will face a harsh reckoning of that ancient agricultural wisdom, You reap what you sow.
We don’t have a paywall because, as a nonprofit publication, our mission is to inform, educate and inspire action to protect our living world. Which is why we rely on readers like you for support. If you believe in the work we do, please consider making a tax-deductible year-end donation to our Green Journalism Fund.Donate
Get four issues of the magazine at the discounted rate of $20.