What would you say if I suggested that we could cut damaging greenhouse gas emissions worldwide by a quarter without any impact on our current fossil fuel burn?  And that we could do this with surprisingly little investment or new technology?  Would you not hail me as a climate change hero?  Award me the blogging prize and pack me off to Copenhagen?

On the other hand you might just send for the men in white coats - but if you did I should shout ‘World Bank, World Bank, World Bank’ - at you, very loudly.

Because this is indeed the implication of what former and current World Bank environmental experts Robert Goodland and Jeff Anhang seem to be saying in a paper in the current issue of World Watch Magazine. 

In essence, they argue, with good supporting evidence, that the proportion of greenhouse gases emitted by the production of livestock for human consumption has been massively underestimated.  

The United Nations Food and Agriculture Organisation in a study three years ago estimated this figure at 18 per cent. Goodland and Anhang are now suggesting that this is little more than a third of the what it is in reality.  Their estimate is 51 per cent.  A figure that is, of course, growing as the world becomes more affluent and the vast populations in the developing world move towards cities and adopt a diet that contains ever higher proportions of meat and dairy foodstuffs. 

Most of us know that livestock have a particularly damaging effect because they are emit methane as a product of digestion.  This gas is twenty-five times more powerful in its greenhouse effects than our old friend carbon dioxide, although in mitigation it does also disappear more quickly from the atmosphere.

But it is not just the fact the the world’s 1.4 billion cows each have a greater warming effect than a car.  For most cattle - and certainly the ones that produce our dairy products - do not graze quietly on mountain pastures suitable for no other purpose than growing grass, like the Salers cow in the photograph.  Rather they demand protein and oil based feed, crops that need to be grown on good soil and then manufactured and transported.

Even before you take into account the deforestation to provide land to grow feed crops like soya, the carbon expended in tilling the soil, in fertilisers, in transporting the products, in packaging and refrigeration adds massively to the carbon footprint of the livestock industry.   We also waste a great proportion of the meat we buy.

When everything is added together, according to the these authors, the contribution of the livestock industry to global warming totals 51 per cent.  It therefore follows that if everyone consumed half the quantity of meat and dairy products that they do now - and most of us in the developed world consume far too much - then we should slash greenhouse gas emissions by more than a quarter.

Of course this doesn’t mean we all simply give up eating meat.  No-one is suggesting that as a course of action.  You can’t have yoghurt or cheese without fresh milk and you can’t have fresh milk without calves.  Half of those calves will inevitably be bull calves.  And the only thing you can do with 99 bull calves out of 100 is to fatten them up and eat them.  That is, if you want to have milk.

Similarly you can’t have eggs without chickens and fifty per cent of eggs that hatch will be cockerels.

So there is no need to give up meat and dairy in in their entirety.  Nor is all livestock equally polluting.  Chickens, for instance have a far lower carbon footprint per kilo than cows.  And upland pastures that cover large areas of the world can only sensibly be used for raising premium, slow-growing livestock - such as the Salers cow in my photograph.

But cereals and vegetables, of course, need even less.  The 1970’s self-sufficiency guru, John Seymour, used to claim that you could feed a family of four on an acre of beans (and given the variety of species of bean and the almost infinite number of ways of cooking them there would be no reason to become bored).  In the space you would need to produce a kilo of beef you could produce 6 kilos of eggs or 2.3 kilos of pork - neither of which emit greenhouse has as potently as the cattle.

So reducing our consumption of meat and dairy products - would have a dramatic effect on greenhouse gases. But it would have many other benefits as well.  We know that there are  major differences in the levels of heart disease and cancers of the digestive tract between those countries like the USA where the average annual meat consumption is 123 kilos a year, and India where it is around 3 kilos, or even Japan at 40 kilos.  

But the real benefit would come from simply being able to feed the world’s population from the growth of which comes a threat to the future of mankind far greater than climate change.  Unless the world’s population can be stabilised - and at the moment it is die to reach 9 billion before then end of the century up 50 per cent from today, then we shall simply overwhelm the resources of the world.  

But the world’s population will not stabilise until all the world’s peoples achieve a certain level of development.  That will not be possible if the world then demands meat and dairy products, even at the European level of about 70 kilos a year.  So measures to reduce livestock consumption now by encouraging the manufacture of ever tastier vegetable substitutes for meat and dairy products will help everyone in a variety of ways.

Reducing consumption will paradoxically even help the farming community. Cut out the carbon-expensive commodity production of cheap meat and you allow farmers to charge a premium for low carbon sustainable production.  Everyone wins. Cut the cheap meat at Copenhagen!

Picture shows a cow of the Salers variety that live naturally on the upland volcanic pastures of the southern Auvergne in Central France and definitely a cow worth preserving.