It’s been well reported thatplant-based diets对环境的影响更好，因为生长的植物比饲养牲畜产生的温室气体排放量少，而且总体上需要更少的水和土地利用。但是所有的研究都可能有些混乱，例如，最近出版的白皮书赞扬美国牛肉的最小环境影响，由National Cattlemen’s Beef Association。白皮书概述了“美国牛肉生产的最小环境足迹”，理由是美国可持续生产牛肉的所有方式，并且在环境影响方面正在继续改善。
对于动物产品行业的人们来说，这是一个可怕的时刻。美国最大的牛奶生产商Dean Foods刚刚申请第11章破产，指责消费牛奶的生产下降。调查显示人们吃的肉少，而是可能正在努力流行的基于植物的产品，例如不可能和超越。对于我们所有生活在这个星球上的人来说，这也是一个可怕的时刻，这是专家所说的确定性气候紧急情况。随着越来越多的专家鼓励人们遏制其肉类消耗以谋取地球的利益，看来牛肉行业正在试图用自己的可持续发展努力的报告来抵消这种叙述。
当然，肉类和乳制品行业将通过自资助的研究和白皮书分享自己的观点，普林斯顿大学研究学者兼世界资源研究所（WRI）的研究学者蒂姆·索格林（Tim Searchinger）指出。Searchinger最近撰写了有关如何创造可持续的食物未来。尽管来自行业协会的报告可能包含真实的事实，但它们也倾向于包括一些值得怀疑的事物。Searchinger打破了一些国家Cattlemen的牛肉协会的亮点，以将其全部置于上下文中，并为我们提供更广泛的描述，了解可持续牛肉的真实情况。
牛肉说：碳排放计算是错误的
国家牧民的牛肉协会表示，由于全球关于温室气体排放的统计数据如何被误认为是美国特定的统计数据，以及牛肉排放量如何与所有牲畜的混乱。“在全球范围内，牲畜产量（从饲料生产到消费者的排放）的生命周期排放量是温室气排放的14.5％，”白皮书中的据《白皮书》。Global beef life cycle emissions are 6% of the world’s greenhouse gas emissions, they add, and for the U.S. specifically, they say, citing the EPA, just 3.3% of the country’s greenhouse gas emissions come from beef cattle, in the form of feed production, fuel and electricity use, and methane and nitrous oxide emitted by cow burps and manure.
但是Searchinger说这不是准确的，因为这个数字没有考虑到为牛养殖的土地。That means the beef industry is ignoring the emissions that are a result of converting land to use for livestock—both the energy it takes to convert that land and the fact that farmland doesn’t absorb as much CO2 from our atmosphere as the forests that it replaced. “About a third of the carbon in our atmosphere is there because of the conversion of land to agriculture,” says Searchinger. “In order to produce all of this beef, we’ve had to clear a huge amount of forest, which is true even in the U.S.”
尽管牛肉行业可能会说这并不重要，因为所有土地已经转变为农业用途，但这也不是整个故事。Searchinger说：“随着[牛肉]的全球消费增加，我们需要清理更多土地。”另外，这并不是说土地无法回到森林，这将有助于从空中吸收更多的二氧化碳。他补充说：“我们清理了所有这些土地，人们说，‘好吧，忘记了’，但是我们这样做的每英亩土地都可能是一英亩的土地。”“当农业签约时，森林再生。”考虑到土地，WRI计算出，牛肉产量约占美国总温室排放量的15％。
牛肉说：但是我们不如运输
大牛肉指向交通工具，说它并不像所有散发温室气体的飞机，火车和汽车那样糟糕。Cattlemen协会写道：“为了将美国牛肉的产量进一步融入观点，包括牛奶以及其他动物和作物农业在内的所有农业都占美国温室气体排放量的8.4％。”“相对，运输占美国温室气排放的28％。”但是，由于一些原因，这种比较并没有真正的意义。这并不像美国人在吃汉堡之间选择or驾车兜风。同样，这些计算再次忽略了土地利用对农业的环境影响。Searchinger说，最后，这只是一个“愚蠢”的论点，因为这并不重要：两者都对许多环境损害负责。
“They obviously don’t want the message to be that people should eat less beef, but it’s like anything else,” he says. “We want the world’s cars to be more efficient . . . but that doesn’t mean we want people to drive more.” Overall, people有吃的牛肉少了；美国人普通吃饭现在比1970年代少的牛肉少了根据2017年数据。但是事实是，人口水平上的总牛肉消费基本上保持不变，这是因为我们的人口增长。Searchinger说：“因此，如果不是人们消耗牛肉少的事实，我们就必须清理更多的土地。”“显然，人们（少吃）的效果很大。”
牛肉说：与其他国家相比，美国牛肉是最有效的
The National Cattlemen’s Beef Association says U.S.-grown beef is more sustainable than beef from other countries—”The U.S. has one of the lowest beef GHG emissions intensities: 10–50 times lower than other parts of the world,” they write—and this one is actually true, but it comes with a pretty big caveat. “The bottom line is that beef is inherently a very inefficient food,” Searchinger says. “There are huge environmental implications involved in producing beef. That’s true wherever it’s produced.” The crux of why, he notes, is because it takes about 50 to 100 calories of feed to produce 1 calorie of beef, meaning lots of land set aside for cattle, which is less land for forests that can sequester CO2.
美国表现出色的一件事是最大化生产：“由于精致的遗传学和营养的进步，美国牛肉的生产约为世界牛肉的18％，其中8％的牛群生产了世界牛群的8％。”“给定量生产的牛肉所需的牛更少意味着温室气体排放量较少，产生人类营养所需的自然资源较少。”这意味着我们从较少的土地中获得了更多的汉堡，而农业土地更少是积极的。
Though the Cattlemen’s Association says that “cattle can convert plants with little to no nutritional value often found on these lands into a high-quality protein,” that’s only taking into account the grass intentionally planted on that land for cattle to graze, as if that’s the only option. American cows aren’t just fed grass that humans can’t eat; they’re fed grain, and if we took all that grain given to U.S. livestock (beyond just beef),它可以养活近8亿人。Searchinger说：“我们每公斤牛肉的使用量较少，但我们仍在通过玉米提供的玉米提供，这是人们可食用的。”
牛肉说：我们总是变得更加可持续
Finally, the beef industry promises it’s getting better and more efficient every year—making advancements in everything from grazing land management and methane-inhibitors to water recycling technology and manure composting, which it says are “just a few of the examples of new technologies being deployed and tested that will further enhance the sustainability of U.S. beef production.” But that might not really matter. Even with large gains in the meat industry, WRI projects that emissions from the industry will rise, and that’s because our population will continue to grow. Overall, says Searchinger, we need to eat less beef, and that’s most true for Americans. “Most of the world eats staggeringly little meat and dairy. If everyone in the world ate the same amount of beef we do in the U.S., we’d need another planet,” he says.
WRI thinks the average American should eat closer to the equivalent of a hamburger and a half a week, instead of the current three-hamburger-per-week average consumption. But as they say, less is always more.