SYDNEY (Reuters) - Farming kangaroos instead of sheep and cattle in Australia could cut by almost a quarter the greenhouse gases produced by grazing livestock, which account for 11 percent of the nation’s annual emissions, said a new study.

Removing seven million cattle and 36 million sheep by 2020 and replacing them with 175 million kangaroos, to produce the same amount of meat, could lower national greenhouse gases by 3 percent a year, said the University of New South Wales study.

Methane from the foregut of cattle and sheep constitutes 11 percent of Australia’s total greenhouse emissions, but kangaroos produce negligible amounts of methane, said the study.

The study said methane was a principal concern in climate change because more than 500 million metric tons of the gas entered the atmosphere annually, which exceeds the amount that can be naturally removed.

Methane’s warming potential over a 100-year time frame is 21 times higher than that of carbon dioxide, but its chemical lifetime in the atmosphere is only 8 to 12 years compared with carbon dioxide’s 100 years.

“Therefore, reducing methane production is an attractive short-term target for mitigating global warming,” said the study published in the latest edition of the international journal “Conservation Letters”.

However, the study said changing farming practices in Australia, which is one of the world’s top wool and beef producers but sells by comparison only small amounts of kangaroo meat for human consumption, would not be easy.

“The change will require large cultural and social adjustments and reinvestment. One of the impediments to change is protective legislation and the status of kangaroos as a national icon,” it said.

The kangaroo is on Australia’s coat of arms, but farmers regard the country’s 34 million kangaroos as pests that compete for grazing pastures with sheep and cattle.

Australia is trying to develop a carbon emissions trading system by 2010, but the government has said agriculture would be excluded from the scheme.

Australia’s greenhouse emissions totals 576 million metric tons of carbon dioxide equivalent, or about 1.5 percent of world emissions. But Australia emits 28.1 metric tons of carbon per person, the highest per capita in the developed world and five times more per person than China, due to use of coal for electricity.

Transport and energy accounts for the largest amount of emissions, at 69.6 percent, with agriculture creating 15.6 percent. Sheep and cattle alone produce 10.9 percent of emissions.

The study said farmers had few options to reduce greenhouse gas emissions other than changing feed stock, reducing livestock numbers or changing species. The study cited the growth of wildlife industries such as springbok farming in South Africa, red deer in Britain and bison in the United States.

“Using kangaroos to produce low-emission meat is an option for the Australian rangelands...and could even have global application,” said the study.