Desenrola, Rio #243: O lixo nas praias durante o ver?o

Why wild venison is a climate-friendly swap for beef

In countries like Scotland where deer populations are tubidy de jogosculled, eating wild venison can be a low-carbon option.

My last meat feast was seven years ago. My parents -were visiting me in London from Costa Rica and we spent the evening going through the brief but rich menu of a small steak restaurant. For them, it was their final meal before returning home; for me, a farewell to my most carnivorous days.

In the years since I've kept a diet of mostly vegetarian dishes, bits of seafood and the occasional exception. As this diet emerged from my work covering climate change, I pick and choose with that in mind: if an animal product is low carbon, like mussels, it will be on my plate regularly. Meat?–?a high-carbon food – features on my plate for special meals, like my mum's pork leg for Christmas, or on the rare occasion I really crave something like the Costa Rican pork belly-based specialty chifrijo.

Each person has their own approach to climate-friendly food; mine is to reduce food-related emissions, not to have a perfect vegetarian scorecard.

Since I moved to Scotland a few years ago, a new wrinkle has appeared: venison?– the meat from deer. Deer populations are out of hand here: the Scottish Government estimates that the overall population could be around one million, up from half a million in 1990. Deer are thriving, partly because humans eradicated their predators, such as wolves and lynx centuries ago.

In response, deer populations are culled every year to keep numbers in check. In my pragmatic climate diet, venison felt like fair game as long as it came from wild deer.

But, was it? This question was on my mind when I was dining at a cosy pub in Mallaig in the Scottish Highlands and spotted venison steak on the menu. Could wild deer really feature in a climate-conscious diet?

"I think the answer here is clearly yes," says Matthew Moran, a professor of biology at Hendrix College in Arkansas, US. Moran co-authored a study in 2020 on the potential carbon savings of wild game harvests in the US.

When Moran's team added up all the animals hunted in US, it was the equivalent of over 3% of all meat consumption nationally. They then asked themselves by how much the country could reduce its meat-related emissions if those hunters swapped shop-bought beef or chicken for their prey (90% of them deer and their relatives).

Their conclusion? The emissions' reduction was equivalent to removing 400,000 cars from the road each year.

"The main reason being is that if you harvest deer from the wild as a food source, there is little or no habitat destruction," Moran explains, "unlike what is involved in raising meat on farms".

Moran's argument rings true, but the answer gets messier the deeper you look. Venison can be a low-carbon option if the deer are not farmed and truly wild. As a meal, wild venison can have a small carbon footprint, as long as hunters don't travel a long way to cull the deer.

Venison can form part of climate-friendly diets on a local level, but the issue grows complicated when considered on a global scale.

"The problem is scale," says Hannah Ritchie, deputy editor and lead researcher at Our World in Data, an organisation that makes scientific data accessible and understandable, and a global development researcher at the University of Oxford in the UK.

"Yes, it might be a reasonable – and low-carbon – choice for a small percentage of the UK population to eat wild venison, but the numbers just don't work for any critical mass of people," she says.

To explore this question, I started with a simpler one: how can one know if something you're eating contributes to climate change?

Beef is a good example of a high-carbon food. The emissions related to all beef cattle are around 5% of global emissions.

When forests or grasslands are cleared to make way for grazing fields and for crops that become animal feed, they release carbon dioxide to the atmosphere. When cows digest food, they naturally produce masses of methane, a potent warming gas. And then there's the fuel used to transport cattle to fields and slaughterhouses, the energy used by retail and storage facilities and every other material involved in the process.

Take all the greenhouse gas emissions associated with beef and divide them by how many burgers you can produce, and you have your carbon footprint per burger.

To produce 100 grams of protein from beef (scientists often use protein as a handy equivalent to compare different foods), on average 25 kg of carbon dioxide equivalent (CO2e) is released. Producing the same amount of protein from peas, results in 0.4 kg of CO2e. Tofu releases 1.6kg, chicken generates 4.3kg and pork 6.5kg of CO23 per 100g of protein.

CO2 equivalent, or CO2e, is the metric used to quantify the emissions from various greenhouse gases on the basis of their capacity to warm the atmosphere – their global warming potential.

The gap between meat and other sources of non-animal protein is high. So, how does the venison steak on the menu at Mallaig compare?

Firstly, I had to make sure that this was wild, and not farmed, venison. The entire appeal of wild venison, compared to industrial meat, is that you're not rearing additional animals in warehouses or pens – and finding farmed venison on a menu in Scotland is not uncommon, despite the abundant local wild supply.

I asked the waitress about this, and she said their venison came from Knoydart, the wild and remote peninsula across the loch from Mallaig. Satisfied, I ordered one. Being wild or not, it turns out, is the first big question.

In February 2024, the Scottish Venison Association commissioned a report to estimate the carbon footprint of country's wild venison. The authors tracked factors such as the fuel used by vehicles driven by deer managers and by hunters, the energy used in the processing facility and the methane released by deer themselves. Deer are ruminant animals, just like cows, sheep and goats. This means they have more than one stomach chamber and belch out methane when they digest their food. Methane is a highly potent gas, which, although shorter-lived in the atmosphere, has a global warming impact?84 times higher than carbon dioxide (CO2) over a 20-year period.

According to the Scottish Venison Association's report, producing 100 grams of protein from wild venison, generates 11.9kg of CO2e. And while this is not the same method as the study that compared different protein sources, it gives a ballpark estimate: less than beef, but higher than chicken and pork. Hardly a climate-friendly meal.

But there's a big caveat: over 90% of this footprint comes from deer themselves. And this opens a debate between experts doing the bean-counting for greenhouse gas emissions.

"There's a fundamental [carbon] accounting question: wild deer would exist and produce methane regardless of whether they're culled for venison – so should it count?" says University of Edinburgh academic Christopher Hirst, who authored a 2021 report on wild deer and carbon sequestration in Scotland that concluded that deer densities need to be reduced to reach climate targets.

In a separate study in northern Italy, researchers analysing licensed hunting culls, also found that if they counted the methane from deer, the carbon footprint of venison ballooned?– overtaking even that of beef in some circumstances.

And here is the nerdy question at the heart of venison's carbon footprint: should you count the methane from wild deer in a venison burger?

If this was a beef burger, the answer would be an emphatic yes. The cow was bred specifically for human consumption, so her methane (the largest chunk of a cow's greenhouse gas output) is impossible to distance from the burger.

In the case of venison, Hirst and others argue that "wild deer populations are not being maintained at these high levels for venison production". In Scotland, where one million deer roam the country, most wild venison is a byproduct of culling programmes required to protect the Scottish landscape from overgrazing.

"These deer would exist?– and emit methane?– regardless of whether they're culled and their meat is subsequently utilised for food," says Hirst, who is currently undertaking a PhD focusing on deer and forest management at the University of Edinburgh.

Experts like Hirst acknowledge a critique to this idea: that there is nothing natural about deer numbers in Scotland (and elsewhere where they need culling), as they reflect how humans have removed predators, altered their habitat and often fight back against efforts to control populations.

But in places where culling takes place, and deer meat is available, would it not make sense to use it? If we take the view that deer's methane should not be counted, the climate impact of Scottish venison would be much, much lower than beef, and lower than chicken and pork. According to the Italian study, deer would also be a much more sustainable option than beef, but not quite as climate-friendly as chicken and pork.

Once you've established whether deer is wild or not, one must turn to the hunters as the next big issue. Both in the Italian and the Scottish studies, around 90% of non-methane emissions came from the petrol used by hunters and by others in the industry.

And the hunters, it turns out, hold the key to making my venison steak low carbon or not.

"If you travel a long distance to hunt, then any greenhouse gas savings are probably lost in what is produced by the travel vehicle," says Moran.

More like this:

? Why do we throw away the best bit of the fruit?

? The benefits and risks of foraging your own food

? Is alcohol a secret polluter?

By now, I'm hoping that my steak was the result of a local hunter near Mallaig or Knoydart. And I'm also praying that they are very good at their jobs. The Italian case study explains why.

Its researchers were extremely thorough and counted all hunters for the 2015 season (there were 168) and noted down how many deer they each managed to kill: from a disappointing zero to the allowed maximum of four. Collectively, they culled 140 red deer.

According to this study, 71 hunters (who travelled on average 818km or 508 miles) went home empty handed. And bad shooters are bad for the carbon footprint of venison.

The Italian researchers put it this way: if these 71 people would have stayed home, the remaining 97 hunters could have killed the 140 red deer, they would not have the burden of the petrol-related emissions of the bad-shooters and the carbon footprint per kilogram of venison would roughly half.

Should we be more selective about who gets a hunting license to lower venison emissions? Or – a more surprising solution suggested in the study -– invest in better training for hunters?

But this is deep in the weeds and, as Ritchie puts it: "we're missing the bigger picture here" by zooming so closely into the exact number of emissions linked to each gram of venison protein.

Ritchie is referring to the fact that you can't feed the masses with wild venison. Even if you killed every single deer in Scotland, you would not remotely meet the country's meat supply. The US case study confirms this: the entire national wild game harvest accounted for only 3% of meat calorie intake.

"The carbon footprint is almost beside the point: we just can't get anywhere close to meeting our meat demand with wild animals," Ritchie points out.

But there's another reason why eating venison might be good for the climate.

Many countries have climate targets that depend on trees sucking carbon dioxide out of the atmosphere via photosynthesis and storing it in themselves and underground. That is why there has been a myriad of projects in recent decades to expand and protect woodlands.

But deer are hungry animals that will happily eat young trees and new shoots of old ones. At very high densities in some parts of the US, up to 75% of seedlings were damaged. In Scotland, a survey in 2013 found deer impact 15-20% of young trees.

"Without controlling deer populations, new woodland creations and existing woodlands will not achieve their carbon sequestration potential," says Hirst, who authored the report on how wild deer affect carbon sequestration in Scottish woodlands.

There are no studies showing how much greenhouse gases could be kept out of the atmosphere by culling deer in Scotland, but scientists like Hirst agree that reducing deer would increase carbon storage.

Forestry and Land Scotland spent ￡38.8m (around $55m) between 2014 and 2019 on deer management. While a small offset came from their venison sales, which accounted for about ￡9m ($12.1m) in that period (there are other venison dealers in the country), it is an expensive activity.

"Increasing venison consumption from wild deer in Scotland could be part of an approach to support the ongoing management of deer in Scotland, both for climate goals and landscape recovery," Hirst says.

But there are barriers to consumers picking venison off the shelves, Hirst says, including price, availability and cooking habits. Those must be overcome to make venison a regular part of people's diets.

"My personal opinion is that vegetarianism is basically a niche diet that will never be popular amongst the majority of people," says Moran. "Eliminating meat seems unlikely to succeed because of personal preference. So, my argument is that encouraging wild game consumption will satisfy many people's meat desires, but in a more sustainable way."

Looking back, I wonder whether the venison steak I ate came from a deer shot by an efficient local hunter.

I asked myself the same when my mother-in-law made a venison stew from strips she bought at Knoydart (steak was too pricey, stir-fry strips were more affordable) or when I spotted venison at a tasting menu in an upmarket restaurant.

In the past, I would have only asked to the waiter: "Excuse me, is this wild or farmed venison?" Now I know there's more to it than that. But in a country with a rampant deer population, it feels like a reasonable protein source.

When I visited the Kinross Livestock Fair, near Loch Leven in Fife, a few weeks ago, there was a stall selling a variety of burgers – beef, beetroot, chicken and venison.

I quizzed the server, who was confident in her replies. "Yes, it is wild deer. Yes, it was shot locally" – less than 20 miles (32.2km) away, in Cupar. And then it was my turn to say yes. The venison burger was delicious.

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