07/21/2014 05:30 EDT | Updated 09/20/2014 05:59 EDT

Beef's environmental costs are exceptionally high

There's an easy way for you to reduce your greenhouse gas emissions, help preserve biodiversity and reduce water pollution all at the same time, scientists say: Don't eat beef.

A new study by U.S. and Israeli researchers compared the environmental costs of producing beef, dairy, poultry, pork and eggs per calorie or gram of protein. It found that all sources had similar environmental impacts, except for beef, which:

- Used 28 times more land, potentially destroying natural habitats where wild plants and animals live.

- Consumed 11 times more irrigation water for feed.

- Released five times more greenhouse gases, which are linked to global warming.

- Used six times more nitrogen fertilizer, which can pollute waterways, causing problems such as algae blooms that foul lakes.

The larger impact of cattle is mainly because the big, slow-growing animals need more food to produce a kilogram of protein than smaller, faster growing farm animals. However, cattle also have some peculiarities, such as their tendency to belch methane, a potent greenhouse gas.

"The best way in this context to lower your environmental impact is to eliminate beef whenever possible and replace it with other sources of sustenance," said Gidon Eshel, an environmental physics professor at Bard College in Annandale-on-Hudson in New York who led the study, in an interview with CBC News. The study was published Monday in the Proceedings of the National Academy of Sciences.

Eshel told The Associated Press that the average American who switches from beef to pork would reduce the equivalent of 540 kilograms of carbon dioxide a year, which is about nine days' worth of the nation's per capita greenhouse gas emissions or the emissions from 230 litres of gas, according to the U.S. Environmental Protection Agency.

But what you choose to eat instead of beef doesn't matter so much, since they all have a similar impact, suggested the report, which was co-authored by researchers at Yale University in New Haven, Conn., and the Wiezmann Institute of Science in Israel.

Dietary choices make difference

Eshel said he hopes the study will help people recognize that their dietary choices can make a significant difference.

While previous studies had looked at the impact of certain farm products with respect to certain environmental impacts, the study by Eshel and his colleagues pooled together data on the five top sources of protein eaten in the U.S. and analyzed them all the same way for four different environmental impacts.

The data they used was publicly available from agencies such as the U.S. Department of Agriculture, the U.S. Department of Energy, and the U.S. Geological Survey.

The researchers took care to take into account complexities such as the difference in resource use between cattle in feedlots and those that graze on arid land, while designing an analysis that was uniform for beef, dairy, pork, poultry and eggs.

"What it gives rise to is a much clearer view of how the various categories stack up against each other," said Eshel, who does not eat meat, dairy, or eggs, but said he was an "Israel cowboy" who raised cattle in his "distant youth."

Canada likely similar

While the study looked specifically at the U.S., Eshel said results would probably be similar in most industrialized nations, since they have similar farming practices.

"For developing nations," he added, "that's a whole different story."

Even within the U.S,. he acknowledged, the degree of some of the environmental impacts depends on location. For example, there are growing water shortages in the western U.S., but fresh water is abundant in eastern North America, so using large amounts may not have that much impact.

Similarly, in Canada, the water used in cattle production in Ontario and Quebec may be less of an issue.

Beef producers have also argued that because the land used to ranch cattle can't be used to grow crops, it doesn't matter that much.

Eshel disagrees. He said when land is used for cattle ranching, it destroys the habitat used by wild plants and animals. In some cases, that might include endangered species.

"You may say these lands may very well not be able to produce any other human-destined calories, but is it really something that we need so badly – those calories – that we're willing to sacrifice those species?" Eshel asked. "In my calculus, perhaps no."