I prefer not to eat food that has a face. But many of my nearest and dearest love their meat, and who am I to ask them not to eat so much of it? Until now, that is.

Having just discovered the huge impact of livestock production on global warming, I need hesitate no longer. Reducing our meat consumption is no longer an option but an urgent necessity. Here’s why.

Eighteen per cent of the greenhouse gas emissions that we produce come from the production of livestock – that’s 4 per cent more than from transport. That’s not all, as the amount of meat and dairy produce consumed globally is set roughly to double by 2050: so if there’s a problem now, how big will it be by then?

You might wonder why official concern over climate change has focused so strongly on carbon offsetting, greening your home and cutting your transport and has all but neglected the huge role played by our consumption of meat and dairy products. Could it be fear of being seen as the nanny state? Has our dietary choice become a sacred cow?

Sadly it’s cows themselves who are a big part of the problem, churning out massive amounts of methane in their burps and farts, and yet more from the decomposition of their liquid slurry. Carbon dioxide emissions are greatest from the massive deforestation carried out, mainly in Brazil, to raise beef cattle or to grow swaths of soya beans for turning into animal feed, a valuable export. Further noxious emissions, such as nitrous oxide, are released from manure and from the use of nitrogen fertiliser to grow feed crops for animals.

Livestock farming has many other adverse effects on the global environment, being the largest source of water pollution and degradation of coastal areas and coral reefs. In some parts of the world overgrazing is harming biodiversity and pasture lands; elsewhere it is turning more and more pastures to desert. In addition the livestock sector is responsible for more than 8 per cent of human water use. This doesn’t sound huge, but is important at a time when water shortage is becoming a critical issue in many parts of the world.

Globally between a third and a half of the world’s cereal harvest and most of the soya is fed to intensively farmed animals. Yet much of the nutritional value of the feed is lost in its “conversion” to meat. The predicted doubling in the numbers of animals will increase the likelihood of global pandemics, often associated with the intensification of livestock farming. And if we don’t act to stop climate change, we know that it is the poor who will become the environmental refugees.

We can’t ignore either the compelling argument of animal welfare. The thought of twice as many pigs confined in crowded concrete pens, billions more meat chickens limping painfully through their short lives in their ammonia-ridden sheds and more dairy cows bred to produce yet more milk and struggling to cope with the physiological strains this level of production places on them: to me, this is a nightmare.

Studies in Europe, America and Japan have shown that the more meat in your diet, the greater the global warming potential and the lower its energy efficiency in your body. If you eat a portion of pasta with frozen broccoli and peas it will be roughly three times more energy-efficient than pasta with beef and twice as energy-efficient as pasta with pork. To put it another way, producing your average Sunday joint of roast beef results in greenhouse gas emissions equivalent to driving from London to Manchester.

We may not all want to be vegans – though the time to mock their plant-based diet is long gone – but we can all take steps to alter our own eating habits. We can all take the “Big Food Challenge”.

Based on the best scientific evidence to date, in a report out today Compassion in World Farming calculates that to reduce our impact on climate change we need to reduce consumption of meat and dairy products in line with government carbon reduction targets, that is, by one third by 2020 and by 60 per cent by 2050. That could mean having a couple of meat-free days a week, reducing the amount of meat (for example, eating one lamb chop, not two) or, more likely, increasing the number of meat-free meals and maybe substituting dairy milk and cream with equivalents made from soya beans or oats at some meals.

As for the impact of this type of dietary change on your own health – why, only last month The Lancet published an article from public health experts in three countries, which said that cutting meat consumption in developed countries from the current 200-250g per person per day to 90g per day would help to reduce obesity and have several other health benefits, including a likely reduction in colorectal cancer.

Compassion in World Farming wants us to take the Big Food Challenge (more at www.ciwf.org/globalwarning) and reduce our meat and dairy consumption. When we buy animal products it recommends paying a little more for the organic or free-range equivalent. We can all be adventurous too, and try foods such as tofu and tempeh and find out the best ways to cook them. If you eat a varied diet, you know you will not be missing out on vital nutrients.

So, to benefit the planet, the animals and your own health, why not join me and take the Big Food Challenge?

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