This story originally appeared on Slate and is republished here as part of the Climate Desk collaboration.

The meat industry is one of the top contributors to climate change, directly and indirectly producing about 14.5 percent of the world's anthropogenic greenhouse gas emissions, and global meat consumption is on the rise. People generally like eating meat—when poor people start making more money, they almost invariably start buying more meat. As the population grows and eats more animal products, the consequences for climate change, pollution, and land use could be catastrophic.

Attempts to reduce meat consumption usually focus on baby steps—Meatless Monday and "vegan before 6," passable fake chicken, and in vitro burgers. If the world is going to eat less meat, it's going to have to be coaxed and cajoled into doing it, according to conventional wisdom.

But what if the convincing were the easy part? Suppose everyone in the world voluntarily stopped eating meat, en masse. I know it's not actually going to happen. But the best-case scenario from a climate perspective would be if all 7 billion of us woke up one day and realized that PETA was right all along. If this collective change of spirit came to pass, like Peter Singer's dearest fantasy come true, what would the ramifications be?

At least one research team has run the numbers on what global veganism would mean for the planet. In 2009 researchers from the Netherlands Environmental Assessment Agency published their projections of the greenhouse gas consequences if humanity came to eat less meat, no meat, or no animal products at all. The researchers predicted that universal veganism would reduce agriculture-related carbon emissions by 17 percent, methane emissions by 24 percent, and nitrous oxide emissions by 21 percent by 2050. Universal vegetarianism would result in similarly impressive reductions in greenhouse gas emissions. What's more, the Dutch researchers found that worldwide vegetarianism or veganism would achieve these gains at a much lower cost than a purely energy-focused intervention involving carbon taxes and renewable energy technology. The upshot: Universal eschewal of meat wouldn't single-handedly stave off global warming, but it would go a long way toward mitigating climate change.

The Dutch researchers didn't take into account what else might happen if everyone gave up meat. "In this scenario study we have ignored possible socio-economic implications such as the effect of health changes on GDP and population numbers," wrote Elke Stehfest and her colleagues. "We have not analyzed the agro-economic consequences of the dietary changes and its implications; such consequences might not only involve transition costs, but also impacts on land prices. The costs that are associated with this transition might obviously offset some of the gains discussed here."

Indeed. If the world actually did collectively go vegetarian or vegan over the course of a decade or two, it's reasonable to think the economy would tank. According to "Livestock's Long Shadow," the influential 2006 U.N. report about meat's devastating environmental effects, livestock production accounts for 1.4 percent of the world's total GDP. The production and sale of animal products account for 1.3 billion people's jobs, and 987 million of those people are poor. If demand for meat were to disappear overnight, those people's livelihoods would disappear, and they would have to find new ways of making money. Now, some of them—like the industrial farmers who grow the corn that currently goes to feed animals on factory farms—would be in a position to adapt by shifting to in-demand plant-based food production. Others, namely the "huge number of people involved in livestock for lack of an alternative, particularly in Africa and Asia," would probably be out of luck. (Things would be better for the global poor involved in the livestock trade if everyone continued to consume other animal products, such as eggs, milk, and wool, than if everyone decided to go vegan.) As the economy adjusted to the sudden lack of demand for meat products, we would expect to see widespread suffering and social unrest.

A second major ramification of global vegetarianism would be expanses of new land available. Currently, grazing land for ruminants—cows and their kin—accounts for a staggering 26 percent of the world's ice-free land surface. The Dutch scientists predict that 2.7 billion hectares (about 10.4 million square miles) of that grazing land would be freed up by global vegetarianism, along with 100 million hectares (about 386,000 square miles) of land that's currently used to grow crops for livestock. Not all of this land would be suitable for humans, but surely it stands to reason that this sudden influx of new territory would make land much cheaper on the whole.

A third major ramification of global vegetarianism would be that the risk of antibiotic-resistant infections would plummet. Currently, the routine use of antibiotics in animal farming to promote weight gain and prevent illness in unsanitary conditions is a major contributor to antibiotic resistance. Last year the Centers for Disease Control and Prevention announced that at least 2 million Americans fall ill from antibiotic-resistant pathogens every year and declared that "much of antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe." The overprescription of antibiotics for humans plays a big role in antibiotic resistance, but eradicating the factory farms from which many antibiotic-resistant bacteria emerge would make it more likely that we could continue to count on antibiotics to cure serious illnesses. (For a sense of what a "post-antibiotics future" would look like, read Maryn McKenna's amazing article on the topic for Medium and her story about a possible solution for chicken farming in Slate.)

So what would be the result, in an all-vegetarian world, of the combination of widespread unemployment and economic disruption, millions of square miles of available land, and a lowered risk of antibiotic-resistant gonorrhea? I can only conclude that people would band together to form communes in order to escape capitalism's ruthlessness, squat on the former pasture land, and adopt a lifestyle of free love.

I kid. Mostly. It's easy to get carried away when you're speculating about unlikely scenarios—and sudden intercontinental vegetarianism is very much an unlikely scenario.

But if the result of a worldwide shift to a plant-based diet sounds like a right-winger's worst nightmare, it's worth pointing out that continuing to eat as much meat as we currently do promises to result in a left-winger's worst nightmare: In a world of untrammeled global warming, where disastrous weather events are routine, global conflicts will increase, only the wealthy will thrive, and the poor will suffer.

Let's try a middle path. We're not all going to become vegetarians, but most of us can stop giving our money to factory farms—the biggest and worst offenders, from a pollution and public health perspective. We can eat less meat than we currently do, especially meat from methane-releasing ruminants (cattle, sheep, goats, etc.). Just because a sudden global conversion to vegetarianism would have jarring effects doesn't mean we can't gradually reduce our consumption of meat, giving the market time to adjust. We not only can; we must. After all, with the world's population slated to grow to 9 billion by 2050, we'll be needing to take some of the 25 percent of the world's land area back from the cows.


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肉类加工业对气候变化的影响非常大，直接或间接地产生了14.5%的温室气体排放量，而且全球肉类消费一直在增长。一般来说，人们喜欢吃肉——穷人赚到钱后几乎总要买肉。人口和肉制品消费的增长将会对气候变化，人口质量和土地使用产生灾难性的影响。

减少肉类消费的尝试还处在起步阶段——“无肉星期一”和“6点之前吃素食”活动，人造假鸡肉和试管汉堡（注：这种汉堡所取用的汉堡肉，不需要通过屠宰动物获得，而是在实验室里“培养”出来的）。传统观点认为，如果人们开始减少会用肉类，那么也将渐渐养成这种习惯。

但是假如世界上每个人都自愿停止吃肉，这种劝说是否会变得容易？我想这种情况不容易出现。某一天，如果大家醒来后都意识到善待动物组织宣传的口号是对的，那么对改善气候来说，这是最好的情况。如果大家都做出这种共同的改变，就像彼得·辛格（注：澳大利亚哲学家、动物解放主义人士）梦寐以求的事情实现了，那么结果会如何？

至少，一个研究小组已经假设了素食主义对地球的影响。在2009年，荷兰环境评估署发布了一项预测——如果人类逐渐减少消费，停止食用或者生产肉制品，其会对温室气体产生的影响。研究者们预测，到2050年，全球范围的素食主义将减少17%的农业碳排放，24%甲烷排放和一氧化氮排放。广泛的素食主义在减少温室气体排放方面也能产生同样的作用。而且，荷兰的研究者们发现，相对于纯粹的致力于减少能源消耗的碳税和能量重复利用技术，全球范围的素食主义在达到上述效果的同时成本更低。结果就是，普遍的减少肉食不会单方面的减缓全球变暖，改善气候变化任重道远。

荷兰研究者没有考虑如果人人都不吃肉，还会发生什么。“在这项研究中，我们忽略了可能对社会经济方面的影响，比如健康改变对GDP和人口数量的影响”，Elke Stehfest和他的同事写道，“我们没有分析饮食变化对农业经济造成的后果以及由此带来的影响。这不仅包括转型成本，还包括对土地价格的影响。转型所产生的成本也许会很明显地抵消掉我们之前提到的成就。”

确实如此。如果整个世界都吃素或者素食主义实行十年或二十年，我们认为经济会衰退。根据2006年联合国关于食用肉制品对环境毁灭性影响的报告《畜牧业的阴影》，畜牧业产品占世界GDP总量的1.4%。动物产品的生产和销售为13亿人提供了工作，其中有9.87亿都是穷人。如果一夜之间肉类的需求都消失了，这些人赖以生存的方式就没有了，就不得不寻找新的方式维生。现在，一些人，像为动物农场提供玉米饲料的农民可以开始种植受欢迎的植物产品。而另外一些人，比如那些大量的除了畜牧业没有其他工作可做的，尤其是亚洲和非洲国家的人就没有这么幸运了（如果人们继续消费其他动物产品，像鸡蛋，牛奶和羊毛，而不是完全素食主义，那么情况就会好很多）。经济在适应突如其来的肉类产品的滞销同时，我们可以预料到普遍的艰难和社会动荡。

世界范围的素食主义带来的第二个重大影响是有更多可利用的土地。目前，反刍动物像奶牛及其同类的牧场占据了世界上未被冰覆盖的土地的26%。荷兰科学家预测世界范围内的素食主义将使27亿公顷（约1.4万平方千米）的牧场被释放，包括近期用于种植动物饲料的1亿公顷（约386平方千米）。并不是所有这些土地都适合人类使用，但可以肯定的是，从整体上来看，这些突然增加的土地会使其变得更加便宜。

全球素食主义带来的第三个重大影响是抗药性传染病将直线下降。目前，在动物农场中，为了给牲畜增重，在不卫生的环境下保持健康，抗生素被普遍使用，这就成为抗药性的主要原因。去年疾病防控中心宣称，每年至少有200万美国人因感染抗药性病原体生病，而且“很多动物抗生素的使用都是不必要，不合理的，只会让人们更加不健康”。在人类身上的抗生素滥用在抗药性的产生过程中也难逃其咎，但是，如果忽视许多抗药细菌来自于农场的事实，我们会以为还能继续寄希望于抗生素来治疗疾病（想要了解什么是“后抗生素时代”，请阅读麦肯那的《媒介》，以及关于如何在养鸡场解决该问题的方法。文章刊载于Slate杂志）。

那么，在一个纯素食主义的世界，普遍的失业，经济衰退，数百万平方米的土地空置，抗药性风险低的淋病同时并存，会产生什么样的结果？我只能推测，人们会团结起来建立公社以逃避资本主义的剥削，抵制之前的牧场开采，自由恋爱。

哈哈，我是开玩笑的。很多时候，当你推测不可能发生的事情的时候，很容易得意忘形——突然之间同步的洲际素食主义简直不可能发生。但是如果全球性地坚持素食主义，这对于右翼分子来说简直是噩梦，但是值得指出的是如果继续保持现在的肉制品消费量，这无疑将会是左翼分子的噩梦：在一个全球变暖失控的世界，气候灾害频发，国际冲突也会增加，只有富人能够发展，穷人只会忍受更多痛苦。

那么让我们取折中路线。我们不会都变成纯素食主义者，但是大多数人可以停止将钱投入农场——污染和公共问题的罪魁祸首。我们可以吃更少的肉，特别是产生甲烷的反刍动物（牛，山羊，绵羊等）的肉。突然之间的全球性的素食主义会产生不良后果，不代表我们不能逐步减少现在的肉类消费，给市场调整的时间。我们能够这样做，也必须这样做。毕竟，随着世界人口不断增长，到2050年人口将增至90亿，我们将需要把约25%的土地从牛羊那里夺回来。