Hello and welcome to this issue’s Big Green Debate. This issue we’re tackling the rather meaty subject of the most sustainable diet for the planet. Richard Sagar will be outlining the case for a vegan diet, while Karen Leach will be making the case for flexitarianism. As usual there may or may not be a certain element of Devil’s Advocate in these articles.

Julien Pritchard


While there are also issues of biodiversity loss, nitrogen production, peak phosphorus, not to mention the extraordinary amount of suffering the consumption of animal products is responsible for, for brevities sake I’ll focus on two primary issues as to why a vegan diet is the most sustainable.

i) Greenhouse Gas emissions

The Food and Agricultural Organization of the United Nations (UN FAO) has demonstrated that animal production for food is responsible for more Greenhouse Gas (GHG) emissions than all of transport combined1. The distance the food travels, so called ‘food miles’, is trivial in comparison, accounting for as little as a few percent of the overall emissions2. As comedian and satirist Bill Maher has quipped, you’re probably better off eating a salad in a hummer, than a cheeseburger in a Prius.

Even if you consume food from locally produced grass fed beef and dairy cows, which may be better from an animal welfare perspective, they’re worse from a climate perspective. Due to an onNo average 50% increase in methane emissions;a greenhouse gas 24-25 times more potent than carbon dioxide.

As the graph from the US Department of Agriculture demonstrates, a vegan diet produces the lowest amount of GHG emissions.

ii) Food Waste

We feed enormous amounts of soy beans and grain to animals that could otherwise be used to feed people. From the calories in the food we feed animals, we only get between and 10% to 30% return in the meat, eggs and dairy which result. I take it as given that people concerned with susNotainable development should abhor wasting natural resources. Animal products in our diet are responsible for a staggering amount of wasted food, far more than results from global biofuel production.

Perhaps my opponent will claim that a reduction in our use of animal products will suffice, a so-called ‘flexitarian’ approach. While of course this is preferable to the consumption of large quantities of animal products, it still isn’t as sustainable as a vegan lifestyle. With lower rates of heart disease and obesity as a by-product, a cruelty-free vegan lifestyle is truly the most sustainable.   Richard Sagar


There’s clear evidence, and common sense, around the normally greater environmental efficiency of eating vegetable protein ourselves rather than feeding it to animals and eating the animal.

But more than with our other environmental impacts (e.g. few people commit to never use motorised transport) with eating animal products there is a growing tendency towards absolutism: not to focus on reduction, or on the impacts of the whole spectrum of buying, storing and cooking food, but on the specific solution of veganism. I see this absolutist expectation as unhelpful from a sustainability perspective for several reasons:

1) Culture and alienation: when people who are ‘not like us’ share food with us, it seems poorer in spirit to refuse than to break one’s own food rules. Do you refuse animal products cooked by your gran who’s eaten them for 80 years? Or from generous Muslim neighbours breaking their Ramadan fasts? Absolutism alienates those around us.

2) Waste: It is surely better to eat someone’s Macdonald’s burger than see it put in the bin, or to snaffle the conference buffet remains than go home to make your own vegan dinner? Is it really an environmental act to send soup back to the pub kitchen to be thrown away on account of a miniscule cream garnish?

3) Transitional systems and economics: I’d rather support my Welsh GM-campaigner organic grass-fed beef farmer friend than see Pembrokeshire farming go to the wall. For our farming to transition to sustainability over time, it first needs to survive! It then needs to be supported to become less resource-intensive. Even in the longer term a small proportion of livestock in mixed farming can create an excellent permaculture model. In the wild, or what passes for it, shooting rabbits and deer for food plays the essential ‘top predator’ role in habitats we have already disrupted.

Reduced use of animal products is environmentally crucial: veganism is not. Like other areas of change, diet change involves systems and people, and needs to work with those systems and people to enable them to change over time.   Karen Leach