How Sustainable Is Your Holiday Lamb?

by Ryan Nebeker


Lamb is a traditional symbol of springtime, and that’s one of the most popular times to eat it: Americans consume about a pound per person each year, and 20 percent of that happens around Easter, Passover and other springtime holidays. Lamb’s popularity among immigrant communities and as a halal meat helps keep demand high during the rest of the year. Whenever you shop for it, you might have noticed that most of the lamb in the grocery store is stamped with an Australia or New Zealand country of origin label. Over half the lamb eaten in the US is imported, but why? And what does this mean for sustainability?

The Difference Between American and Australian Lamb

One of the primary differences between American lamb and that New Zealand and Australian lamb is diet. Most lamb from New Zealand and Australia is entirely raised on grass. Just like grass-fed beef, grass-fed lamb is lean. It also has a stronger, “gamey” taste.  However, most Americans prefer a milder, beef-like flavor. To accommodate this, American lamb producers raise their animals mostly on grass, but supplement their diets with grain, usually corn and soy, before slaughter. This makes the meat a little fattier and more beef-like. This finishing step can happen on the same farm where they’re pasture-fed grass, but it also happens on CAFOs, or factory farms

This difference in diet is also partially economic, which in turn explains why so much of the lamb we see in the grocery store is imported. The US has a lot of pastureland to support grazing animals like sheep and cattle, but it has a lot of corn and soy production too. Most cattle in the US eat a high proportion of those grains because it helps them put on weight quickly and get to market faster. This makes feeding cattle in the US more profitable compared to sheep, which spend more of their lives grazing on pasture even if they are finished on a grain diet. In contrast, the generally mild climates and vast rangelands of the sheep-producing regions of Australia and New Zealand make maintaining year-round pasture easy, which keeps production costs for sheep very low. There’s little reason for farmers in Australia and New Zealand to use grain, and they’re able to ship a cheaper product to consumers around the world. 

The Carbon Footprint of Lamb

Intuitively, a local product should have a lower carbon footprint than an imported one because it doesn’t have to travel as far. But the reality is a little more complicated. There are a lot of factors that determine a carbon footprint, and food miles are only part of the equation. When it comes to animals like sheep and cows, what they eat, where they live and how they’re raised makes a big difference. Cow burps have gotten a lot of attention as a major source of greenhouse gasses, but sheep are ruminants too, and they have the same complicated digestive system that uses bacteria to help break down tough plants. This allows them to digest grass, but it also means they produce methane, which is a more powerful greenhouse gas than carbon dioxide. Other stages of raising sheep, like growing feed, irrigating and fertilizing pastures and running equipment also contribute to the overall carbon footprint of lamb.

Diet can change the carbon footprint of lamb: A 2013 study of 60 lamb farms in the UK found grain-finished lamb had a significantly higher carbon footprint than lamb that was entirely pastured. More recent research from California found less clear results: farms that finished lambs on grain had slightly lower carbon footprints than those that didn’t. In both cases, the grain-grass divide was less important than other factors like altitude and the breed of sheep. 

Most of the emissions in lamb production come from the sheep burping methane, a finding backed by other work from New Zealand. This was true even when researchers included the entire refrigeration and shipping chain to get lamb to the UK from New Zealand, suggesting food miles are less important than how lambs are raised. Overall, studies of the carbon footprint of lamb suggest that it’s very similar to beef, with about 10 to 20 kilograms of carbon dioxide produced per kilogram of finished lamb. 

Do Carbon Footprints Overlook the Benefits of Grazing?

Significantly, none of the studies examined whether or not raising sheep on pasture put more carbon into soil, which is a major benefit of raising animals on pasture. Soil can store a lot of carbon, which accumulates as plant roots and manure decomposes. Most grain farming disturbs soil and causes this carbon to disappear. Carefully managed grazing, on the other hand, has the potential to add carbon to the soil; grass roots stay in place, and animals are constantly adding fresh fertilizer in the form of manure. Studies from beef production have shown that taking soil carbon into account can radically change the footprint of meat, even making it carbon negative

Soil carbon can be hard to measure, so it hasn’t been included in many studies of sheep. Still, some data from Europe suggests that well-managed sheep grazing can increase soil carbon in alpine pastures. The authors of the California study also pointed out that even if carbon benefits are unclear, there are a number of other benefits to grazing sheep. They can naturally manage weeds and efficiently turn waste — like the stubble of harvested crops in a field — into food.

Pastured and Local Lamb

Carbon footprinting isn’t the only measure of sustainability that matters, especially since it might undercount carbon stored in the soil. Given the broad environmental benefits of pastured meat, choosing pastured lamb is a better choice than a grain-finished animal,  so grocery store Australian lamb isn’t the worst option. However, even if food miles aren’t the biggest contributor to a carbon footprint, there are plenty of other reasons to choose a local product over an imported one. Fortunately, this doesn’t have to mean buying lamb that was finished on a feedlot. Growing interest in more sustainable meat means that more American farms are raising lamb entirely on pasture and selling through farmers’ markets, CSAs and local butchers. Options like pasture-raised halal lamb are also becoming more common. Especially given the recent loss of the restaurant market during the coronavirus crisis, many pasture-raised meat producers are looking for new customers and opening business to direct orders. Wherever possible, try to choose organic — grass-fed lamb producers may use chemical fertilizers on their pastures. Depending on where you are in the country, local lamb availability varies seasonally, so be sure to ask your butcher or farmer when the freshest product comes in. 

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