Every five years, the government tries to tell Americans what to put in their bellies. Eat more vegetables. Dial back the fats. It’s all based on the best available science for leading a healthy life. But the best available science also has a lot to say about what those food choices do to the environment, and some researchers are annoyed that new dietary recommendations of the USDA (United States Department of Agriculture) released yesterday seem to utterly ignore that fact.

        Broadly, the 2016-2020 dietary recommendations aim for balance: More vegetables, leaner meats and far less sugar.

        But Americans consume more calories per capita than almost any other country in the world. So the things Americans eat have a huge impact on climate change. Soil tilling releases carbon dioxide, and delivery vehicles emit exhaust. The government’s dietary guidelines could have done a lot to lower that climate cost. Not just because of their position of authority: The guidelines drive billions of dollars of food production through federal programs like school lunches and nutrition assistance for the needy.

        On its own, plant and animal agriculture contributes 9 percent of all the country’s greenhouse gas emissions. That’s not counting the fuel burned in transportation, processing, refrigeration, and other waypoints between farm and belly. Red meats are among the biggest and most notorious emitters, but trucking a salad from California to Minnesota in January also carries a significant burden. And greenhouse gas emissions aren’t the whole story. Food production is the largest user of fresh water, largest contributor to the loss of biodiversity, and a major contributor to using up natural resources.

        All of these points and more showed up in the Dietary Guidelines Advisory Committee’s scientific report, released last February. Miriam Nelson chaired the subcommittee in charge of sustainability for the report, and is disappointed that eating less meat and buying local food aren’t in the final product. “Especially if you consider that eating less meat, especially red and processed, has health benefits,” she says.

        So what happened? The official response is that sustainability falls too far outside the guidelines’ official scope, which is to provide “nutritional and dietary information.”

        Possibly the agencies in charge of drafting the decisions are too close to the industries they are supposed to regulate. On one hand, the USDA is compiling dietary advice. On the other, their clients are US agriculture companies.

        The line about keeping the guidelines’ scope to nutrition and diet doesn’t ring quite right with researchers. David Wallinga, for example, says “In previous guidelines, they’ve always been concerned with things like food security—which is presumably the mission of the USDA. You absolutely need to be worried about climate impacts and future sustainability if you want secure food in the future.”

解析：B。根据题干中的food security和David Wallinga可定位至原文最后两句。定位句提到，大卫·沃林加说：“在以前的指南中，他们一直关注类似食品安全这样的问题——这想必是美国农业部的使命所在。如果想要确保未来食品的安全性（food security），你绝对需要担心气候的影响和未来的可持续性（future sustainability）。B项表述与此一致，故正确答案为B。

错项排除：A项利用food security进行干扰，原文倒数第二句说到，美国农业部一直在关注类似食品安全这样的问题，但并没有提到食品安全问题是其最优先处理的问题（top priority），而且这也不是大卫·沃林加针对食品安全提出的建议，故A项错误。大卫·沃林加并没有说到要与各个行业紧密合作（cooperating with the industries），故排除C项。D项利用原文最后一句中出现的climate impacts进行干扰，但大卫·沃林加强调是需要重点关注气候影响和未来的可持续性，与食品生产没有关系，故D项错误。