With Sir Paul McCartney campaigning for people to abstain from eating meat one day a week, an animal welfare group has highlighted the negative impact that livestock rearing can have on the environment.

According to Vegetarians International Voice for Animals (Viva!), animals bred and transported for meat are the second largest cause of greenhouse gas (GHG) emissions, exceeding all other sectors apart from power generation.

Tony Wardle, associate director of the group, cited figures from the United Nations’ Food and Agriculture Organisation (FAO) suggesting that livestock is responsible for 18 percent of all GHG emissions.

That is significantly more than the 13.5 percent attributed to cars, aeroplanes, trains, ships and other forms of mechanised transport.

Mr Wardle said: “The knowledge that livestock production is devastating the planet has actually been around for a couple of decades, but it was brought to a head [in 2006] by the FAO.

“To give up meat for one day a week is a step forward. To give it up entirely and go vegetarian or vegan would be far, far better,” he added.

In an interview with the Independent this week, Sir Paul discussed the launch of his Meat Free Monday campaign.

The former Beatle has enlisted the help of Hollywood actor Kevin Spacey and entrepreneur Sir Richard Branson in highlighting the effect of the meat industry on climate change.