As the economic, political and personal costs of doing nothing to mitigate climate change skyrocket, there's one lifestyle change that slashes dietary greenhouse gas emissions in half: Veganism.

Climate change is predicted to cost the U.S. billions of dollars by mid-century, poses a growing national security threat , and will make some regions of America "unsuited for outdoor activity."

A new report published in the journal Climatic Change compared greenhouse gas emissions attributable to more than 55,000 meat-eaters, fish-eaters, vegetarians and vegans in the U.K. The researchers found that meat-eaters' dietary greenhouse gas emissions were twice as high as vegans'.

The production, transportation and storage of food greatly contributes to emissions , the study points out. These emissions range from carbon dioxide related to fossil fuels used to power farm machinery, to the methane released by livestock. Animal-based products tend to release more emissions than plant-based products due to the methane animals can produce and the inefficiencies in growing livestock feed.

According to the U.S. Environmental Protection Agency, agricultural practices contribute 14 percent of global greenhouse gas emissions .

The study found that mean dietary greenhouse gas emissions (results reported for women and then men) was 46 percent and 51 percent higher than for fish-eaters, 50 percent and 54 percent higher than for vegetarians, and 99 percent and 102 percent higher than for vegans.

"Reducing the intake of meat and other animal based products can make a valuable contribution to climate change mitigation," the report concluded.

Past research showed similar results. A study in April found that annual agricultural carbon emissions could be reduced up to 90 percent by 2030 with agriculture adjustments, including a reduction in global beef consumption.

Environmental Working Group produced a chart comparing the impact of different meats, and found that if all Americans chose a vegetarian diet, the environmental impact would be equivalent to removing 46 million cars from the road. But the group cautioned in 2011 that a dietary shift in the U.S. would make a "moderate dent in overall carbon emissions," and political action is needed as well.

President Barack Obama earlier this month unveiled new standards for power plants, calling for a 30 percent reduction in their carbon emissions by 2030.