"Methane, mostly generated by animals bred for human consumption, is nearly thirty times more heat retaining than carbon dioxide but takes only eight years to cycle out of the atmosphere. 20% of the greenhouse gases generated are attributed to meat and dairy consumption."

NO -- or rather, only indirectly. Animals can't digest cellulose. Many animals eat cellulose but it's up to bacteria and other micro organisms in their guts to do the breakdown for them. It is these bacteria that in the course of their metabolic processes produce the methane. They do this whenever they are digesting plant matter, whether that's in the gut of a rumenant or in a compost pile (it would of course be a different population of microflora). Or in the duff layer of the soil.

That's how it works. Plants use sunlight to turn carbon dioxide and water into the material of their bodies, they eventually die, and micro-organisms break that back down relasing oxygen and carbon dioxide and some of them methane (mainly anaerobes do that). Which is why, by the way, global warming will result in the release of a lot more methane when in the tundra conditions grow warm enough for micro-organisms to grow faster on the organic matter that has built up under eons of colder condition where "rotting" is slow.

STOP! This is NOT an argument against veganism per se. Plenty of good ethical arguments. Just an argument against this pseudo scientific reason. It is also not an argument in favor of factory farming or the amount of animall products consumed. But it IS an arguement against an "anti-life" approach. Life involves growth and death, living and decay, eating and being eaten. It might not strike you as being pretty, Nature might seem cruel and uncaring, but that's how "life" is and some of us, instead of fleeing in horror, embrace it.

No pseudo-scientific reasoning at work here, just information about the causes of human generated greenhouse gases. And logic.

How animals generate methane is incidental; interesting, but incidental. Methane generated by other means (such as the permafrost receding @ 10m pa) is also a consequence.
However, it is only just being recognised that meat and dairy is the second largest man-induced cause of greenhouse gases, below the largest (energy/power generation, 50% give or take) and above transport (12%, of which 3% is air transport). Food overall generates 32%, with 20% as a result of meat and dairy consumption. And yes, I know rice generates methane because it’s grown in water and that is 8% - but in the UK we don’t need to eat rice or have it transported halfway round the world, so I choose not to.

So the logic is that I can only make a difference to greenhouse gases in my lifetime by reducing my methane generation, and that is only if I stop eating meat and dairy. Reducing carbon dioxide in the atmosphere is extremely important, and that’s a combination of not producing as much and taking more out somehow – but I by myself cannot influence this significantly or directly, that’s our governments and big business. So logically I am left with me and my diet.

The vegan ethics remain but are irrelevant to the justification for “saving the planet with your knife and fork”. Lots of work is put into doing something about energy and transport, but little about the meat/dairy issue. We all justify what we do, and meat-eaters are no different, until they see a reason to change. Veganism has three key messages – healthy planet, healthy humans, healthy animals. We don’t need to eat meat and dairy, and it’s harmful, so why bother? The normal meat-eating response (and this was mine for a long time) is that ‘I like the taste’ – doing something just because you like to doesn’t hold up, scientifically or otherwise. Putting the information out there, and being prepared to debate it, is extremely important – people can then make informed choices rather than just follow food propaganda.

So we've got to erradicate all the animals?

i think what MDN is saying here is that the bacteria ( or thier close relatives) which break down plant matter in animals stomach's will break down plant matter and release methane and CO2 whether it is in animals stomachs or rotting on the forest floor or in yr compost heap or landfill tip..

vegetation grows, dies and is broken down by bacteria releasing CO2 this happens wherever the vegetation ends up wether in or out of animals.

Each termite produces, on average, about half a microgram of methane per day, a seemingly insignificant amount. However, when this is multiplied up by the world population of termites, global methane emission from this source is estimated to be about 20 million tonnes each year. This compares with approximately 44 million tonnes of CO2 for London’s energy use and transport;

...and I could almost think our commenters are politicians by the way they pick up on a point away from the theme!

The point I was making, and will continue to make, is that eating meat and dairy creates greenhouse gases (20% of all 'anthropogenic' or 'human responsible' sources). Because we breed animals for this, if we stop eating meat and dairy then that amount will reduce. The less we eat, the more we reduce the greenhouse gases for which we are responsible - and as methane cycles out of the atmosphere in only 8 years, doing this is the only thing we can personally do to affect climate change in our lifetime.

There are lots of other sources of methane in the natural world that are pretty much in balance; there is, at the moment, no reason to get rid of those sources by, for example, killing all the termites - that's what the food chain is there for. The difference with humans is that we have a choice, and because we don't need to eat meat to live, a logical choice (if people choose) is to make a difference to climate change as soon as we can. Am I suggesting killing all the hundreds of millions of animals that are bred "because we like the taste"? Not at all (and these are all killed before the end of their 'natural' lives anyway) - but if the demand for meat and dairy reduces, then fewer animals will be bred (and killed) in future.

Funny how many people will happily protest and demonstrate about coal and/or nuclear power, and expect everyone to stop driving cars and walk/cycle everywhere, but so few people are prepared to take direct and immediate action on food because it affects what they 'like'. Ho hum.

ok the termite comment was facile but you are equally guilty of ignoring my main point that vegetation relates methane however it breaks down; whether in the guts of animals destined for the dining table or in a compost heap or on the forest floor

eat meat or not but plants will grow die or be killed/eaten be broken down by bacteria and in the process elease methane and CO2 - be a vegetarian be a vegan- fine- lots of good ethical and environmental reasons but this isnt one of them unless you are also suggesting that the land formerly used for animal fodder is stripped of all vegetation?

the industry associated with meat production as with most modern food production however may not be so "carbon neutral" though

I'm just guessing here, but in the natural state plants would live a long time before dying and rotting away to produce methane.

When crops are used to feed animals they are sown and harvested very quickly, so the methane production is more frequent.

And of course it takes several times the amount of crops to feed a person indirectly via meat rather than directly through eating them directly.

Maybe this is the logic behind the fact that veganism is better because it produces less methane?

Following this line of thought, maybe fruitarianism is even better, since it doesn't involve killing the plant! I wouldn't fancy it personally though...