Zeal to ensure clean leafy greens takes bite out of riverside habitat in California
May06

Zeal to ensure clean leafy greens takes bite out of riverside habitat in California

Perceived food safety risk from wildlife drives expensive and unnecessary habitat destruction around farm fields By Liza Lester, ESA communications officer Meticulous attention to food safety is a good thing. As consumers, we like to hear that produce growers and distributers go above and beyond food safety mandates to ensure that healthy fresh fruits and vegetables do not carry bacteria or viruses that can make us sick. But in California’s Salinas Valley, some more vigorous interventions are cutting into the last corners of wildlife habitat and potentially threatening water quality, without evidence of food safety benefits. These policies create tensions between wildlife preservation and food safety where none need exist, say scientists for The Nature Conservancy, writing in the Ecological Society of America’s journal Frontiers in Ecology and the Environment. The study will be published online ahead of print on Monday, May 6th, 2013. “Farming practices for food safety that target wildlife are damaging valuable ecological systems despite low risk from these animals,” said lead author Sasha Gennet. Check the back of your bag of spinach or prepackaged salad greens, and you’ll probably find that they came from the Salinas Valley. Salad is big business in California. In the aftermath of a deadly 2006 Escherichia coli serotype O157:H7 outbreak traced to California spinach, growers and distributers of leafy greens came together to create the California Leafy Green Handler Marketing Agreement (LGMA) on best practices for the industry, enforced by third-party auditors and inspectors. The LGMA established standards for farm work hygiene, produce processing and transport, and proximity to livestock. About 99 percent of California leafy greens now come from participating farms. But produce farmers in the Salinas Valley report pressure from some powerful buyers to take additional precautions not mandated by government or industry standards. These buyers insist that swathes of bare ground wider than a football field is long separate the leafy greens from rivers, wetlands and other wildlife habitat. Other precautions include treating irrigation water with chemicals toxic to fish and amphibians, and setting poisoned bait for rodents. “The California Leafy Green Hander agreement is transparent, flexible and science based,” said Gennet. “Going above and beyond it just creates costs for farmers and doesn’t improve safety.” It also creates costs for wildlife. Although scant evidence exists of risk of food-borne disease spread by wildlife, the risk of rejection of produce by major buyers is too much for most growers to bear, say Gennet and her co-authors. They measured changes in wetlands and riverside habitat in the Salinas Valley between 2005 and 2009, finding 13.3 percent converted to bare ground, crops or otherwise diminished. Widespread introduction of fencing...

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Vegetables under plastic

Weighing the costs and benefits of plastic vegetable greenhouses over conventional vegetable production. By Liza Lester, ESA communications officer The USDA Natural Resources Conservation Service offers “seasonal high tunnel” kits as part of a three year trial to assess the potential of the plastic houses for conserving water and soil, reducing pesticide use, and improving yields for small farmers. Credit, NRCS. THE economic benefits, for small-holders in particular, of intensive vegetable cultivation inside plastic greenhouses have driven a rapid mushrooming of long plastic tents in farmlands worldwide – but principally in China, where they cover 3.3 million hectares and produce approximately US$60 million in produce (2008 figures). In fact, 90% of all greenhouses are in China, and less than 1% of Chinese greenhouses are glass. Covering vegetables with hoops of plastic sheeting conserves water, binds up carbon, shrinks land use, protects against soil erosion and exhaustion, and mitigates problematic dust storms. But this change from conventional vegetable farming has harmful environmental effects as well. Jie Chang and colleagues review the current research and identify gaps in our knowledge in the February issue of ESA’s journal Frontiers in Ecology and the Environment. Plastic greenhouses are cheap, and easy to construct from locally available materials like wood, bamboo, brick, and plastic sheeting. The Chinese government encourages construction with greenhouse-friendly policies, including credit programs to cover start-up costs. The protection from the cold extends the growing season. In the temperate north, this means farmers can have two seasons, and more than double their production. Most farms (90%) in China using plastic greenhouses are small, only 0.1-0.2 hectares, and the extra money is important to farmers with low incomes. It also makes vegetables available to more people in China, particularly during the off-season. Because the plastic catches evaporation and channels the water back to the crop, greenhouse-raised vegetables consume less water. In Shouguang Province on the northwest coast, traditional flood irrigation of conventional vegetable fields uses 8690 cubic meters of water per hectare. Farmers can reduce demand to 7049 m3ha-1 if drip irrigation is installed. Greenhouses need only 4500 m3ha-1 of water, and can get by with only 1800 m3ha-1 using drip irrigation. The difference grants a big advantage to greenhouse farmers in areas where industrial, agricultural and urban users compete fiercely for limited water resources. The plastic cover keeps soil and water in, and some harmful airborne pollutants out. Greenhouse farmers find it more worthwhile to cycle inedible vegetable biomass back into the fields and apply manure. Greater reliance on organic fertilizers means that the soil binds up more carbon than conventional open fields. Greenhouse vegetables need less pesticide and inorganic fertilizer per unit...

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