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Farmers Assaulted by Converging Effects of Climate Change

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How the Tomato-Potato Psyllid Has Affected Agriculture Throughout the World

Pests and Climate Change Threaten Crops World Wide

The Potato-Tomato Psyllid. Photo Courtesy of QuestThere is little doubt that climate change will have and has already had profound global effects on agriculture. While warmer weather means a longer growing season in many regions, with the potential of more harvests and more crop variety each year, it also means more extreme, less predictable, and more pest-friendly weather.

One example of this has been the tomato-potato psyllid, a pest that sucks potato plants dry and transmits a disease that ruins potato chips, giving them a burnt flavor and brown streaks (known as “zebra chip”). With potato chips a $6 billion industry in the U.S., this one pest alone is on a course To impact the economy. Although California growers have dealt with this pest for over 100 years, it has only recently begun to spend the winter. Average temperatures have risen 2-3 degrees F, enough to keep them from being frozen out in the winter. Overwintering psyllids mean the pest is already there when crops are planted in the spring and can start their attack at the very beginning of the growing season, and an early infestation leads to much greater damage than a late one. Warm spring temperatures cue the insects to begin their development early, giving them more time to eat a plant and produce a new generation.

Insects can’t produce their own heat the way mammals do, which has historically kept them following warmer temperatures. Since 1900, the psyllid would move to California, then keep being forced out with sharp cold spells. This pattern began to change in 2000, when it first became apparent that the psyllid was overwintering in Irvine, California. In 2012, scientists discovered that the bugs had spent the winter in areas of Washington, Oregon, and Idaho, the state where half the country’s potato crop is grown. As temperatures warm more, they will be able to overwinter even further north.

Spraying for psyllids is now costing California potato growers about $75/acre, at a time when farmers have been trying hard to reduce pesticide use in response to consumer demand and environmental blight. Less pesticide use could mean fewer volatile organic compounds in the atmosphere. “Warmer temperatures, and the pests that thrive on them, now threaten to undermine those gains,” noted Quest.

Such pests with expanding ranges can be found worldwide. In Tanzania, malaria mosquitos have moved further up Mount Kilimanjaro. In Japan, the green stinkbug, damaging to rice and soybeans, is expanding northward.

Maine’s cranberry harvest, however, has felt more of the benefits than the drawbacks of a warming world – at least for now. The harvest was up this year, part of a steady climb in recent years. Some growers believe that if temperatures rise a little more, parts of Maine could be opened to crops of peaches. Any further increases in temperatures, though, could harm cranberry growers in Massachusetts and New Jersey, while helping the Maine farmers.

An increase in pest activity did accompany the yield rise, however, but many farmers found that they could keep most of the pests in check with organically-approved biological pest control like Bt (Bacillus thuringiensis) and Entrust, a spinosad bacterial pesticide. These two pesticides helped to control the highest fruitworm population in ten years. In the end, despite the infestation from the mild winter, Maine cranberry bogs lost only 5-10 percent of their crop.

Wisconsin, the nation’s largest cranberry-producing state, was hard-hit by the drought, however – an issue that could develop into a larger scourge as climate change worsens. Cranberries need a specific set of conditions, especially adequate moisture at each stage of the fruit’s growth and ripening.

In Norway, meanwhile, many farmers are excited at the prospect of a growing season that could lengthen by up to two months, even three months in the higher elevations. (The growing season is defined as the number of days with an average temperature of at least 5 degrees C.)This means more thermophilic (heat-loving) crops could be grown further north, and yield multiple harvests each summer. Abundant forest growth would also make forests more productive sinks for the greenhouse gas carbon dioxide.

But here, too, insect pests would be the first drawback, followed by weather extremes. Many pests would develop a larger range across the country and the ability to overwinter in new regions, likely preceding their predators. A new wood-decaying fungus could invade more Norwegian forests. As the growing season began earlier, there would also be a greater risk of frost damage to crops and unpredictable weather. Toward the end of the season, despite warmer days, weak daylight in the north would still be a limiting factor.

Climate change has already had a severe impact on the world food supply. Its effects converge on agriculture, including longer seasons of heat, shorter cool seasons, and dwindling water supplies, increasing the vulnerability of food supplies everywhere. Over the last decade, the world price of food has doubled, a remarkable statistic (although a good part of this is likely a result of rising fuel costs). Now, according to Oxfam, the world’s poorest spend 75 percent of their income on food.

Emissions heat up the ocean, which makes it more acidic. This in turn reduces the amount of seafood that can be caught and leaves many fishing nations in jeopardy. In island regions like the Maldives, seafood has traditionally been the cheapest and most available source of protein, and is the primary source of protein for over 1 billion of the world’s poorest people. Rising ocean temperatures can also push fish away from the tropics and toward the poles. Tropical countries dependent on coral reef fisheries are also among the most threatened.

It’s not yet clear what the combined effects will be of these already noticeable problems with looming effects like sea level rise, reduced oxygen, and changes in nitrogen cycles.

On land, drought and extreme weather contributed to record-high corn prices this year. This leads to not only to hunger but to political problems. “As food prices rise, the worldwide competition for control of land and water resources is intensifying,” said Lester Brown, president of the Earth Policy Institute in Washington.

In California’s agricultural Central Valley, salt from the rising ocean is making its way into the water supply, a problem for drinking and irrigation uses alike. According to The Merced Sun-Star, “The crop insurance industry is calculating potential billion-dollar losses from extreme weather conditions, as well as floods and fires that occur in their wake.”

Right now, though, droughts are still the effect that farmers most fear. The federal government’s U.S. Climate Extremes Index, a measure of the frequency and severity of extreme weather, set a record high last year. Its steady upward climb began in the early 1990s.

Adaptation to so many concurrent climate impacts may be the biggest challenge in feeding ourselves in the coming century, especially as we have so little ability to predict the synergy and interaction of the many simultaneous factors. Although Maine cranberry farmers are among the few rejoicing lately, it seems that the long-run costs may far outweigh the benefits to growing crops in a warmer world.

Genevieve Slocum is a Contributor to The Free George.

The Free George is the online magazine and visitors’ guide of Upstate NY, covering things from Albany to Lake Placid, including Saratoga, the Lake George region and the Adirondacks. Check out our City Blogs section for our extended coverage areas as well.

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