Many people choose fish instead of meat to offset their environmental footprints. But if the choice is farmed salmon instead of chicken, then researchers have some unsettling results to share: the environmental impact of these two foods is about the same.
The reason for that is their feed, which is remarkably similar for chicken and salmon, and accounts for the majority of impacts—which are spread across land and sea for both animals.
Chicken and farmed salmon are two of the most widely-consumed foods in western countries, and so the University of California, Santa Barbara-based researchers wanted to understand the full scope of their impacts. This involved calculating the ‘cumulative environmental pressure’ of each species—a calculation that incorporates the greenhouse gas emissions, nutrient pollution, freshwater use and spatial disturbance involved in farming each one, and then maps these geographically. Crucially, the researchers looked beyond the farm gate to include the impacts of feed production for both animals.
This analysis revealed a strikingly similar impact level for chicken and salmon, which mainly boiled down to what they ate. Chickens are produced on land and consume land crops like soy and wheat, but they’re also fed a mixture of fish meal and oil made from wild-caught ocean fish: about 527,000 tonnes of the stuff makes its way into their feed each year. Farmed salmon meanwhile, consume fishmeal as you might expect—but also 2.3 million tonnes of land crops every year.
These feedbases accounted for most of the species’ impact—explaining 79% of the environmental pressures associated with chickens, and 69% of farmed salmon’s. Almost all of the spatial disturbance and freshwater use were caused by the feed produced to raise these livestock. About 55% of the greenhouse gas emissions in each case arose from feed production, too.
The shared feed types also create a surprising 85% overlap between the species in terms of where these impacts occurred across the globe. Despite their huge effects, 95% of these cumulative pressures occurred on an area amounting to less than 5% of the planet’s surface. This area was broadly spread across nations: 75% of the feed production impact for salmon, and 68% for chicken, occurs across the land and coastlines of 20 countries worldwide.
This builds a picture of how and where we might remediate some of the associated environmental harms—starting with the biggest and most overlapping driver, feed. Feed-producing regions on land could be intensified to limit the spread of production elsewhere. Or, environmental mitigation measures could be applied there. For instance, the study found that some feed-producing regions of the world are less efficient than others; these places could be good candidates for interventions to increase crop yields or reduce fertilizer use.
Most importantly, the study reconsiders the idea that chicken and salmon are ‘low-impact’ meats, which is why many people choose them as part of a more sustainable diet. As it turns out, that depends on what you measure.
“We urge researchers, consumers, and policy makers to shift the thinking around fed animal production as being not just ‘‘terrestrial’’ and ‘‘aquatic’’ but rather as fitting on a continuum, exhibiting both reliance and pressure on a huge number of environments and production systems.”
Kuempel et. al. “Environmental footprints of farmed chicken and salmon bridge the land and sea.” Current Biology. 2023.
Image: ©Anthropocene Magazine
