Let's begin by defining the only term in the title of this essay that might admit of some ambiguity: environmentalist. According to the Oxford English Dictionary, an environmentalist is “one who is concerned with protecting and preserving the environment”. To be anything other than an environmentalist in this sense of the word then, is to lack concern for protecting and preserving the environment. And to lack concern for protecting and preserving the environment is to be indifferent to the inescapable fact that a healthy environment is necessary for the survival of the human race; for without clean water, fresh air, and healthy soil, human beings simply cannot live, or at least not for very long.
So, to be anything other than an environmentalist is to be indifferent to protecting and preserving the very system upon which human beings and all other forms of life as we know it rely for survival. Indifference to an issue as important as the survival of one's own species is at the very least unbecoming of a thinking person, and at worst imprudent, myopic, and destructive.
With the exception of certain religious zealots who positively relish the idea of seeing the world engulfed in an apocalyptic conflagration, however, very few thinking people are keen to admit that they are indifferent to the survival of the human race. But the simple fact is that if you are not concerned with protecting and preserving the environment upon which human survival is utterly dependent (which is to say, if you are not an environmentalist), then aren't you, ipso facto, indifferent to human survival itself? For how can someone lack concern for the preservation and protection of that without which human survival is impossible and at the same time claim to be concerned with human survival itself? Because human survival cannot be uncoupled from a healthy environment, there is simply no reconciling not being an environmentalist with the claim that one is concerned for human survival.
Every thinking person should be concerned about the survival of life as we know it on the only planet we have, and should therefore be concerned about protecting and preserving the system upon which life depends: the environment.
Ergo, every thinking person should be an environmentalist.
And every environmentalist should, obviously, do her utmost to support those industries and organizations that adhere to environmentally responsible, sustainable practices and (perhaps more important) should also withdraw her support from those that do not. Being an environmentalist is after all about much more than just separating the refuse from the recyclables and driving less; it's about making informed, considered, rational choices to support industries and organizations whose values and practices are consistent with the principles of environmentalism and to refuse to support those industries and organizations that are destroying the environment upon which we and all other species rely.
And no industry is doing more to destroy the environment than the global animal by-product industry. No other industry in the world uses more natural resources, produces more pollution, or is responsible for more environmental degradation than the industry that produces meat, eggs, and dairy. Consider these statistics:
Animal agriculture is the number one driver of deforestation on the planet. According to a report by the United Nations, 70% of formerly forested land in the Amazon, and 91% that has been deforested since 1970, is now used as pasture for cattle.
Raising animals for food uses 70% of the earth's arable land, equivalent to 30% of all the ice-free surface on the globe.
Animal agriculture accounts for 50-70% of all fresh water used by human beings for all purposes. The production of just one pound of beef requires 2,500 gallons of fresh water.
According to scientists at the World Bank, animal agriculture produces 51% of all man-made greenhouse gases, more than all forms of transportation combined and tripled.
In the United States, untreated animal waste has polluted the ground-water in seventeen states. Thirty-five thousand miles of America's rivers in twenty-two states have been contaminated by the excrement from factory farms. Thirty-five thousand miles is fourteen times the distance from New York to Los Angeles, or one-and-a-half times the circumference of the Earth.
Taking all of the above facts into consideration, it's clear that animal agriculture is not an industry that any sincere environmentalist should be willing to support. In fact, there is no industry that is less deserving of an environmentalist's support than the global animal by-product industry. Whether your primary concern about the environment is climate change, deforestation, water pollution, or water scarcity, there is no way to square a willingness to support animal agriculture with the claim that one is an environmentalist, because a person cannot rightfully claim to be concerned about protecting and preserving the environment if he is unwilling to withdraw his support from the one industry that is doing more than any other to destroy the very environment that he claims to want to protect and preserve.
What does it mean, in practical terms, to withdraw one's support from animal agriculture? It means to stop buying and consuming the products of animal agriculture: meat, eggs, and dairy. It means being vegan.
Ergo, every environmentalist should be a vegan.
To be an environmentalist is to recognize your moral obligation to current and future generations of human beings as well as to the billions of other nonhuman animals with whom we share this planet and our brief time on it. Being vegan allows you to fulfill at least part of that obligation and to spare the lives of thousands of animals in the process.
What thinking person would say no to that?
(Full disclosure: Vegan Future Now has no formal affiliation with People for the Ethical Treatment of Animals. We just think they do awesome work.)