There are much better ways to make a difference than giving up meat and dairy, writes Federated Farmers Vice-President Andrew Hoggard.

How do you know if someone's a vegan? Don't worry, they're certain to tell you.

Just now it seems a good number of people are using social media to let the world know how they are going vegan to save the planet, and there is no end of articles that advise ditching meat and dairy will slow global warming.

Your diet can play a part in reducing greenhouse gas emissions but it's not so simplistic as just giving up meat.

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Firstly, it is vitally important to note that the methane burped by livestock (and also emitted from landfills, wetlands and other sources) has a relatively short lifespan in the atmosphere. It does not accumulate like CO2 does. If the methane emissions are static each year then the concentration in the atmosphere does not change. But it can take up to 1000 years for CO2 to break down, so only getting to zero emissions of this gas will result in no further atmospheric concentrations.

Also, are all these people who are giving up dairy or meat because of the methane emissions also giving up rice? Rice paddies are just as a significant a contributor worldwide to methane emissions as livestock are.

No matter what the food you are eating, a greenhouse gas will have been emitted to produce it. I would argue that milk or meat from 100 per cent pasture diet animals in New Zealand, where methane emissions at present are trending static or declining, might have less impact on warming than say some field crop that require a lot of tractor work to cultivate it, then sprayings, harvesting and following transportation, processing.

There might be a case to be made for some sort of carbon footprint measure on your food packaging, however it would need to be based not on the flawed Global Warming Potential (GWP100) metric that takes no account of the short life of methane and its actual warming impact, but instead the more scientifically sound GWP* metric.

That way those consumers who want to get into all that detail and understand the nitty gritty numbers can do so, but if you're like me the label you really care about is the one with the dollar sign at the front of it.

A simple message that overrides all of this is: Don't waste it. One third of food produced is ultimately thrown away. In the developed world, it gets wasted in our fridges and at our tables; in the developing world, due to poor infrastructure at farm and national level, plenty of it gets wasted on the way from paddock to table.

At an individual level, it's a case of making sure you only buy what you need and that you eat it. If you want to be fussy then check the actual product carbon footprint but keep in mind this will vary from country to country in the same product categories.

Andrew Hoggard. Photo / File
Andrew Hoggard. Photo / File

At an international level, well, the best thing we could do is free up agricultural trade across borders. Greater market access for developing countries, without distorting tariffs and subsidies, will bring better returns for them so they can afford to improve their infrastructure and prevent that wastage.

We see countries like Saudi Arabia trying to be self-sufficient in milk production at an emissions footprint and cost structure far higher than New Zealand, when the common sense solution would be to just import it. There are many examples of government interference in the marketplace, with subsidies, trade barriers, and other dumb policies that lead to food being stockpiled and wasted, and thus the emissions that were generated in producing that food were all for naught.

I know this runs counter to the arguments of many green groups who seem to believe trade is a bad thing and that there is some sort of socialist utopia when it comes to food production. Personally, I think they need to take a trip to Venezuela or North Korea to gain a better understanding. Make it a one-way trip to save on the CO2 emissions.

End of the day, if you're that passionate about saving the planet you want to change your diet, I think you could probably have more impact by just not wasting food, and possibly make some radical adjustments to your holiday arrangements, if they have in the past involved the use of fuel. Let's face it, food is a need, holidays to tropical islands are a want.