Category: Climate change

A few days ago, a group at Oxford University published a report in Nature on the environmental impact of different diets in the UK. https://www.nature.com/articles/s43016-023-00795-w

Broadly speaking, this new report reaches very similar conclusions to a previous study, also undertaken by an Oxford team, published in 2018. In brief, if we are worried about the global environment, then we should eat less meat. Which is hardly surprising in general, but the specific results are striking. The new report focuses on real dietary data, whereas the previous one used assumptions about diet, and is more authoritative in this respect.

The classifications are a little confusing and hence open to misinterpretation. The researchers divided people in their survey into the following categories: vegan, vegetarians, fish-eaters, low meat-eaters (<50 grams/day, averaging 28), medium meat-eaters, and high meat-eaters (>100 grams/day, averaging 140). A typical portion of meat (e.g. chicken breast, portion of mince) is 100-150 grams in UK supermarkets. So high meat-eaters are in effect defined to be people who eat a normal portion of meat once a day on average and low meat-eaters are people who do so once every 4-5 days on average.

“Fish-eaters”, confusingly, eat about 40 grams/day of fish on average. In other words, they are people who have a normal portion of fish about once every 3 days. In the study, medium and high meat-eaters actually eat more fish than fish-eaters! Given that the study finds that fish-eaters have an environmental impact which is only a little larger than vegetarians, it would have been helpful to point this out more strongly than a passing comment in the body of the text. Eating fish every day, in place of meat every day, is not the answer to our climate problems.

On average, high meat-eaters have a carbon footprint roughly double that of low meat-eaters and 4 times that of vegans. Low meat-eaters, fish-eaters and vegetarians are bunched fairly close together. Vegetarians in the study eat more cheese than any other group, which also helps to explain why their carbon footprint is not too different from fish-eaters and low meat-eaters.

Despite the potentially misleading categorization, the study is a useful counter-weight to the large body of material that emphasizes reducing food waste. Of course it’s good to reduce waste, but – in the scheme of things – the research team stresses that what we choose to eat is a much bigger issue than how much of it we leave on the plate. The authors also dismiss the argument often put forward by the farming lobby that sequestration (e.g. through grasses) somehow makes up for the damage done by livestock farming. Along with the argument that British beef is somehow OK because it’s British: there may be some differences between sources, but these are overstated and in any event they’re taken into account in the results.

Setting things in context

There is a widespread tendency to think that climate is an energy problem; that agriculture only makes up about a quarter (or a third, according to the authors of this study) of total greenhouse gas emissions, so we should focus on fossil fuels. A problem with this line of thought is the use of averages: high meat-eaters, predominantly members of the world’s richest decile, have a disproportionately large impact. The authors calculate these individuals, averaging 140 grams/day of meat, each account for around 3.7 tonnes of CO2e per annum from their diet. That is more than 50% of the average per capita total emissions (all activities, including transport, heating, power, material goods, etc. as well as eating) for the global population. In North America, where studies have estimated meat consumption to be typically 250 grams/day, the diet-related per capita emissions exceed this global average for all activities.

(There is an argument that the dietary impact is even higher than this, because the land opportunity costs – around half of the world’s total habitable land area is used for livestock agriculture, one way or another – are not fully quantified.)

This statistical point – that the Developed World diet matters more than is generally reported – is similar in kind to, albeit less egregious than, an analogous argument made with respect to flying. Airline companies are very keen to tell us that aviation only accounts for a few percent of GHG emissions. Leaving the (difficult and generally ignored) issue of radiative forcing (RF) to one side, the key point is that most of the world’s population doesn’t fly. A frequent flyer might clock up >10 tCO2e per annum from flights alone, perhaps twice as much when RF is incorporated into the analysis.

I often have to remind myself about proportionate impacts. Recently, we installed an air-source heat pump in our 5-bedroom house. I estimate that – after the first year during which the ‘cost’ of the embedded emissions in the ASHP manufacture is recovered – it will save around 1-2 tCO2e per annum. That’s about the same saving that results when a single high meat-eater converts to a low meat-eater diet …

Earlier this month, a European Climate Foundation study was released about the climate impact of the war in Ukraine: Climate Damage Caused by Russia’s War in Ukraine, lead author Leonard de Klerk.

The report assesses the full impact of the war over a 12-month period, including direct emissions from military activities, the impact of fires, the sabotage of the Nord Stream 2 pipeline, the emissions associated with re-building towns and infrastructure demolished in the fighting … even the impact of the extra emissions from international flights forced to take detours in order to avoid Russian airspace.

The headline figure is an impact of 120 MtCO2e, broadly equivalent to the annual greenhouse gas emissions of Belgium. The rough breakdown of this is 20% from military activities (burning fuel in land vehicles and planes, making and firing ammunition, building concrete fortifications), 15% from fires, 12% from the pipeline sabotage, 40% associated with the rebuilding requirements, and 10% from diverted aviation.

One thing that is absent from the headline figure is the change in land use – the clearing of tree cover – and the consequent reduction in carbon sequestration.

The report is intended to shock – to highlight that apart from the human cost in the region, there is a global environmental cost. And that wars generally, and military activities generally, go unreported in terms of their climate impact. It is estimated that military emissions – left out of the Paris Agreement – account for around 5% of global greenhouse gas emissions.

While the Ukraine war is very shocking, less publicised military impacts are perhaps even more so. According to the Costs of War project at Brown University, the US military’s activities between 2001 and 2018, including Pakistan, Afghanistan, Iraq and Syria, amount to 440 MtCO2e, nearly 4 times the emissions from the first year of war in Ukraine.

Sticking with Ukraine, the ECF report shows how the direct emissions from military activities are actually surprisingly small, as a proportion of the total impact. About twice as significant are the emissions from the (eventual) rebuilding. The impact from fires is broadly comparable with the figure from military activities. And – perhaps most startling of all – the extra international flight miles account for about half as much.

And this leads to the following train of thought – what we do in peacetime still, in 2023, vastly outweighs the effect of war. The international community – had there been the coordination and will – could have decided to limit the number of flights in order to compensate for their increased length in having to avoid flying over Russia. The result would have been avoided emissions equal to 50% of the impact from the war’s military operations. In Britain, if we all – including companies and government on our behalf – reduced our carbon footprint by about 16%, we would fully compensate for the entire footprint of the war in Ukraine, based on de Klerk’s analysis. In the US, the comparable figure is about 2%.

And while it is right to condemn war in Ukraine, it is also right to see things clearly in historical context. Viz the impact of American military activities in the last couple of decades. Or – going further back – the impact of Britain’s wars, including the destruction of our forests over centuries to build our navies.