I can’t understand how Al Gore can be so passionate about advocating immediate and effective action to combat climate change, while completely ignoring what a 400-page U.N. report (published in 2006) has determined to have the single greatest impact on curtailing the current crisis: adopting a vegan diet!

Farmed animals produce about 130 times as much excrement as the entire human population of the U.S. and is up to 80 times more toxic than human waste. Since factory farms don’t have sewage treatment systems as our cities and towns do, this concentrated slop ends up polluting our water, destroying our topsoil, and contaminating our air. There are no federal guidelines that regulate how factory farms treat, store, and dispose of the trillions of pounds of concentrated, untreated animal excrement that they produce each year. This waste may be left to rot in huge lagoons or sprayed over crop fields. Both of these disposal methods result in run-off that contaminates the soil and water and kills fish and other wildlife. The concentration of parasites, bacteria, and chemical contaminates in animal excrement can wreak havoc on the ecosystems affected by farm run-off, and there are countless reports that humans who live near these farms have suffered from the pollution.

Many leading environmental organizations, including the National Audubon Society, the WorldWatch Institute, the Sierra Club, and the Union of Concerned Scientists, have recognized that raising animals for food damages the environment more than just about anything else that we do. In fact, the animal industry produces more greenhouse gases than all the cars and trucks in the world combined! Carbon dioxide, methane, and nitrous oxide together cause the vast majority of global warming. Raising animals for food is one of the largest sources of carbon dioxide and the single largest source of both methane and nitrous oxide emissions.

It should also be added that hundreds of millions of acres of forest have been cleared to create cropland to grow grain to feed farmed animals. And all around the world, overgrazing by livestock leads to the extinction of indigenous plant and animal species, soil erosion, and eventual desertification that renders once-fertile land barren. Livestock grazing is the number one cause of threatened and extinct species both in the U.S. and in other parts of the world. And the commercial fishing industry is pushing entire oceanic ecosystems to the brink of collapse.

My last point concerns the gross inefficiency of feeding grain to animals, then harvesting their meat or products (milk, eggs). This is why more than 70 percent of the grain and cereals grown in the U.S. are fed to farmed animals. It takes up to 16 pounds of grain to produce just one pound of meat, and even fish on fish farms must be fed 5 pounds of wild-caught fish to produce one pound of farmed fish flesh. The world’s cattle alone consume a quantity of food equal to the caloric needs of 8.7 billion people! About 20 percent of the world’s population, or 1.4 billion people, could be fed with the grain and soybeans fed to U.S. cattle alone.