The carbon footprint of the average American's diet has shrunk by about 9 percent, largely because people are eating less beef, according to a new report.

Changes in the American diet—lower consumption of not only beef, but orange juice, pork, whole milk and chicken—meant that the average American's diet-related greenhouse gas emissions dropped from 1,932 kilograms in 2005 to 1,762 in 2014.

The analysis "just shows that small changes in our diets have impacts," said Sujatha Bergen, a food specialist at the Natural Resources Defense Council. "There's a very concrete association between reduced red meat consumption and reduced emissions."

The biggest contributor to the reduction was a decline in beef consumption of about 19 percent over the course of the decade, adding up to a cumulative reduction of 185 million tons of climate change pollution. Total emissions cuts from dietary changes were 271 million tons. During that time, overall U.S. greenhouse gas emissions averaged more than 6 billion tons a year.

Despite the improvement, the dietary changes pale by comparison to overall American emissions from a wealthy lifestyle. The average American has a carbon footprint of about 16 tons and the average U.S. car accounts for roughly 5 tons of emissions per year. China is the world leader in total carbon pollution, but the average Chinese citizen is responsible for less than half the contribution of the average American.

Americans eat more beef per capita than any other country except Argentina and Uruguay, and beef still contributed more than a third of the United States' diet-related climate emissions — about 34 percent in 2014.

The beef industry, which has been long criticized for its outsized carbon footprint, said Wednesday that NRDC's consumption calculations failed to factor in beef exports, which surged over that timeframe. The industry points to data from the U.S. Department of Agriculture, which says beef production in the U.S. has remained relatively stable, from about 25 billion pounds in 2005 to 24 billion in 2014.

"It's not fair to link consumption numbers domestically to production numbers domestically," said Hillary Makens, a spokesperson for the National Cattlemen's Beef Association.

Sara Place, a research director at the association, said that cattle-related emissions dropped only 6 percent over that time period and only because of a decline in the number of cattle.

"One of the major things that's happened in the beef industry is we're producing more beef with fewer animals," Place explained. "From 1975 to today, it takes a third fewer beef cattle to produce the same amount of beef."

NRDC also looked at food that increased diet-related greenhouse gas emissions. Americans ate more dairy products, including cheese, yogurt and butter, between 2005 and 2014. Like beef, production of dairy products is resource intensive.

Products from livestock, whether beef or dairy, have come under increasing scrutiny in recent years for their emissions. Raising cattle requires large amounts of land and feed, mostly corn and soy, which is heavily fertilized. Processing and applying fertilizer releases nitrous oxide, a gas with nearly 300 times the warming potential of carbon dioxide. Meanwhile, methane is emitted from cattle through their digestive systems and from manure disposal and it has at least 25 times the warming potential of carbon dioxide over a 100-year period.

Bergen warned against drawing any nutritional conclusions from the study, but noted that nutritionists and federal dietary guidelines have long encouraged more consumption of vegetables and less saturated fat.

"We do know that red meat and dairy happen to be high in saturated fats," Bergen said, "and there's a very high correlation between health benefits and environmental benefits."