Yet over 95 percent of meat, dairy and egg products consumed in the U.S. still come from these operations. Even in “green” Marin, most fast food outlets, grocery stores and restaurants rely on factory farms for the food they offer.

The unconscionable suffering inflicted on animals should be reason enough to end these horrific operations. In a recent Washington Post column, Princeton University philosopher Kwame Anthony Appiah identifies factory farming as a practice our descendents will condemn us for, just as we now condemn the once accepted practice of slavery.

The fact that animals experience fear, anger, surprise, sadness, disgust, joy, empathy and compassion is callously ignored on factory farms. Worldwide, 58 billion land animals, including birds, pigs and cows, are slaughtered for food each year; 10 billion in the U.S. That’s 31 million each day in our country alone. Most live miserable lives and die horrific deaths.

Extreme overcrowding on factory farms prohibits many from turning around or stretching their limbs for their entire lives. The dehorning, castration, tail docking and beak-trimming treatments routinely forced on farm animals without painkiller would be punishable by criminal charges if inflicted on our pets.

Since most people say they do not want animals to be abused, supporting factory farms by purchasing their products is inconsistent with most people’s values.

The environmental impacts are also devastating. Livestock production is a major contributor to biodiversity loss, land degradation and water consumption, and contributes at least 18 percent of global greenhouse gas emissions.

Much of this impact comes from growing and fertilizing feed for livestock; 16 pounds of plant protein are needed to produce one pound of beef protein. A U.N. study found that “a shift “… to vegetarianism in the U.S. could reduce land and fertilizer demands of Mississippi Basin crops by over 50 percent, which would return nutrient loads to levels at which the Gulf of Mexico ‘dead zone’ was small or nonexistent.”

Eating vegetarian one day each week reduces environmental impact to a greater extent than eating a completely local diet. Switching to a plant based diet results in greater reductions than switching from a sedan to a Prius.

When it comes to our health, research continues to underscore the impacts of the “Standard American Diet” (SAD), characterized by high consumption of animal products and low consumption of plant based foods. Cultures that eat the reverse of SAD have a lower incidence of obesity, cancer and heart disease. That’s why the American Heart Association, American Cancer Society, American Dietetic Association, and former President Bill Clinton all promote the benefits of a plant based diet.

Some suggest free-range farming as an answer.

While this is a step in the right direction, there is simply insufficient land to pasture the 58 billion animals killed for food each year to meet current global demand. Living sustainably, and compassionately requires a reduction in our reliance on animal products.

Any major social change has relied on people of conscience to highlight indefensible practices and insist on higher standards. Factory farming is a blight on animal welfare, the environment, and human health. What we do with that knowledge defines who we are.

As Jonathan Safran Foer writes in his book, “Eating Animals,” “We can’t pretend ignorance, only indifference. The critique of factory farming has broken into public consciousness. We are the ones of whom it will be fairly asked: What did you do when you learned the truth about eating animals?”