Comment: As people are encouraged to take part in "Veganuary" in the New Year, Dr Jacqueline Rowarth investigates the problems with the idea of eating less meat to save the planet.

Veganuary – the northern hemisphere initiative involving becoming vegan for a month – will not solve climate change.

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Becoming vegan forever will likewise do little, despite the calls to "give up meat to save the planet".

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The problem? There are several.

Firstly, most of the diet-based greenhouse gas (GHG) calculations are based on land growing food for animals instead of directly for humans; this is not the global norm.

Secondly, the calculations do not include the GHG cost of the supplements that are required for most humans to remain healthy while on a vegan diet.

Thirdly, the calculations do not consider the GHG implications of the replacements for materials other than food that traditionally come from animals – leather, wool, tallow, sinews.

We can replace leather shoes or wool suits with those made from materials such as cotton, linen or bamboo, but that means more land under production.

Or they could be made from "synthetic" materials which usually involve the petroleum industry. Polyester, poly-fleece and plastic are all derived from petrochemicals.

Research is under way in replacing petrochemicals with plant-based materials generally derived from maize or sugar cane, but the processes are expensive.

We see this in corn (maize)-starch compost bags available in New Zealand. And anything plant-based requires land under production, chemical use in fertilisers and pesticides, and fossil fuel in management including processing.

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A fourth factor is that on a plant-based diet it is difficult to eat enough protein to promote feeling full, building muscle or preventing muscle loss, without consuming additional processed protein powders.

The response by the body on an animal-protein-free diet is usually to upregulate appetite to increase the protein intake; the result is increased food consumption.

Dr Jacqueline Rowarth. Photo / Supplied
Dr Jacqueline Rowarth. Photo / Supplied

This means more land is required to grow that food, with all the management requirements around crop production mentioned earlier.

Veganuary has its base in the general belief that domesticated animals are responsible for a disproportionate contribution to greenhouse gases, and that the environment and human health would be better without them.

Particularly problematic is point one above - the belief that animals are consuming material that humans could eat directly.

Research from the Food and Agriculture Organisation of the United Nations (FAO) has reported that 86 per cent of livestock diet globally is not human-edible.

Dr Anne Mottet, Livestock Development Officer at FAO has also shown that grazing livestock contribute directly to global food security by producing more highly valuable nutrients for humans, such as proteins, than they consume.

Her calculations for global average indicate that grazing cattle need only 0.6kg of protein from human-edible feed to produce 1kg of protein in milk and meat, which is of higher nutritional quality than the original consumed protein.

Of further interest is that "out of the 2.5 billion ha needed for animal production, 77 per cent are grasslands, with a large share of pastures that could not be converted to croplands and could therefore only be used for grazing animals".

Mottet's research indicates that somewhere between 7 and 13 per cent of beef production comes from feed lot systems, yet most of the concerns about GHG are based on this small percentage.

Although Veganuary won't do much to reduce GHG, it could have an effect on improving awareness of the remarkable variety, as well as quantity, of food available to the modern consumer.

Many people eat more animal protein than required; many waste a considerable amount of food of all types, not just animal protein.

Listen to Jamie Mackay's interview with Dr Jacqueline Rowarth on The Country below:

A factor common to most recommendations for the future is to sort out waste and nutritional imbalance – there are still many people with inadequate access to food.

After decades of improvement (despite global population increasing), the proportion of people under-nourished has started to increase again. The FAO estimates that in 1970 over a quarter of the world's population of 3.7 billion people were undernourished.

By 2015, the proportion had dropped to approximately 10.6 per cent. But in 2017 the number had increased to over 820 million, which is almost 11 per cent of the global population. This is why the Paris Climate Agreement emphasised decreasing GHG without compromising food production. It is also why demonising animal protein is dangerous.

"Animal production, in its many forms, plays an integral role in the food system, making use of marginal lands, turning co-products into edible goods, contributing to crop productivity and turning edible crops into highly nutritious, protein-rich food" said Mottet.

Research is ongoing to create greater efficiencies and to reduce the environmental impact of animals. In New Zealand the GHG have steadily decreased per unit of protein produced, and we are now amongst the most efficient producers of animal protein in the world.

If you want to make a difference for the planet – don't buy stuff for which you don't have an identified use, reconsider booking that flight, and do you really need a fossil fuel- burning car?

- Dr Jacqueline Rowarth CNZM, CRSNZ, HFNZIAHS has a PhD in Soil Science and has been vegetarian for over forty years. She is currently a farmer-elected director of DairyNZ and Ravensdown.