Eating Seafood Can Reduce Your Carbon Footprint, But Some Fish Are Better Than Others
By Amy McDermott
Food is expensive. Not just for pocketbooks, but for the planet. Worldwide, more than 25 percent of greenhouse gas emissions come from food production. That's methane belched from cows and nitrous oxide escaping from soils, as well as fossil fuels burned by tractors, fishing boats and rumbling transport vehicles. Some foods cost more than others.
Seafood has a smaller carbon footprint than other animal proteins, on average, because fishing doesn't require farmland or care of livestock. But even among seafoods, fish and shellfish can have varying impacts.
So what's the best choice? Small schooling species, like anchovies and herring, are the most sustainable options, experts say, based on energy use and emissions of their fisheries. There's no free lunch. The question is, what can the planet afford?
Fishermen unload a catch of anchovy and sardines in Ayvalik, Turkey. OCEANA / María José Cornax
Small schooling fish are low impact because catching them doesn't burn much fossil fuel, the major source of emissions for fisheries.
Ninety percent of the greenhouse gas emissions associated with wild seafood come from fuel use, said Peter Tyedmers, who studies the environmental consequences of food systems at Dalhousie University in Halifax, Nova Scotia.
"If you think about fishing, where does fuel get burned?" he said. "On a fishing boat, it's driving the engine. Some fisheries guzzle more gas than others. It depends how long and how hard the engine works."
Fisheries targeting anchovy, mackerel and similar fish are the most fuel efficient, according to a 2015 study coauthored by Tyedmers. They average less than 80 liters of fuel per ton of catch when fishermen use purse-like nets to surround huge schools of the fish. Because these species swim in dense aggregations, fishermen can locate a swarm, throw a net around the whole thing and pull up thousands of fish in one trip.
Compare this to crustaceans like Australian Tiger prawns or Norway lobster, which can burn more than 10,000 liters of fuel per ton of catch. That's because it takes a lot of gas to drag a heavy prawn net through the water, as does motoring from one lobster trap to another. Scooping up a whole school of fish at once is much more fuel efficient.
Conservation status matters too, said Nathan Pelletier, an ecological economist and industrial ecologist, specializing in food system sustainability at the University of British Columbia. When populations are healthy, there are more fish in the water, so it takes less time and less fuel to fill a net. Overfishing leaves fewer fish out there, so it takes more time and energy to catch the same amount.
"Abundant fisheries, from a climate change perspective, will be less greenhouse gas intensive," Pelletier said. "All else being equal, the more fish there are, the less energy we will have to invest in chasing them around and catching them."
A school of sardines rushes around a diver in Tañon Strait, the largest marine protected area in the Philippines. Dense aggregations of little fish make them a fuel-efficient target for fishermen in other areas. OCEANA / Ferdinand Edralin
On the Half Shell
Farmed mollusks may be another climate-conscious seafood, according to a forthcoming study by ecologist Ray Hilborn, at the University of Washington in Seattle. That's because these shellfish don't need to be fed; they can filter sustenance from the water instead. Animal feed can be a huge consideration when it comes to a farm's carbon footprint.
"From a climate change perspective, what you feed and how much you feed matters a lot," said Tyedmers. "In aquaculture, the big generalization is your greenhouse gas emissions are overwhelmingly driven by your feed inputs."
Farmed fish eat a combination of plant and animal parts, like ground up soy or corn, chicken feathers, animal bones and blood. Each ingredient takes energy to grow or catch, and then more energy to process into pellets or flakes. Farming mollusks sidesteps that issue, because they're filter-feeders, no pellets required.
Hold on though, Pelletier said. The jury is still out on mollusks. They don't need to be fed, but they do take effort to seed, harvest and process for human consumption. Considering the amount of meat on a mussel or oyster, it's a low edible yield for the effort.
Farmed mollusks may look good in theory, but Pelletier says he'd be cautious to endorse them, because "it's mostly shell."
Mussel farmers poke through the rows in Thailand. MKeerati / Shutterstock
Of course, to reduce carbon footprints as much as possible, the best bet is to eat veggies. On average, eating plants has a smaller footprint than eating animals, said Friederike Ziegler, who studies sustainable seafood at the Research Institutes of Sweden, in Gothenburg. But among animal products, seafoods are some of the best, she said. And among seafoods, little fish are the best of the best.
In Sweden, where Ziegler lives and works, the government recommends eating seafood two to three times per week. Most Swedes eat less than that. Small, schooling fish like herring are famously popular in Scandinavia, but even in Sweden, Ziegler said people could eat more fish.
Not everyone can switch to veggies, for both cultural and nutritional reasons. Wild sustainable seafood is the best option, in many parts of the world. When it comes to changing diets, "we have to think about solutions that are culturally appropriate and feasible within their specific contexts," Pelletier said.
Atlantic horse mackerels race beneath Oceana's Ranger at Dacia seamount, Spain. Small oily fish like mackerel are some of the most carbon-conscious seafoods. OCEANA / Carlos Minguell
Climate change looms large over the future. To fight it, think like an ocean predator. Dive into the little fish, with big potential for good.
EcoWatch Daily Newsletter
Mangroves play a vital role in capturing carbon from the atmosphere. Mangrove forests are tremendous assets in the fight to stem the climate crisis. They store more carbon than a rainforest of the same size.
- Protecting Mangroves Can Prevent Billions of Dollars in Global ... ›
- Could the 'Mangrove Effect' Save Coasts From Sea Level Rise ... ›
Monday is World Oceans Day, but how can you celebrate our blue planet while social distancing?
- 5 Things to Know About Earth's Warming Oceans - EcoWatch ›
- Bioluminescent Waves Mesmerize California Beachgoers, Surfers ... ›
- NOAA: 2020 Could Be Warmest Year on Record - EcoWatch ›
- On June 8, We Celebrate Our Oceans, Our Future - EcoWatch ›
- 5 Things to Know About the State of Our Oceans for World Oceans Day ›
By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
This Saturday, June 6, marks National Trails Day, an annual celebration of the remarkable recreational, scenic and hiking trails that crisscross parks nationwide. The event, which started in 1993, honors the National Trail System and calls for volunteers to help with trail maintenance in parks across the country.
- As Protests Rage, Climate Activists Embrace Racial Justice ... ›
- First-Ever Black Birders Week Tackles Racism Outdoors - EcoWatch ›
- 15 EcoWatch Stories on Environmental and Racial Injustice ... ›
- Take a Hike Day Is Around the Bend. What's Your Dream Hike ... ›
By John Letzing
This past Wednesday, when some previously hard-hit countries were able to register daily COVID-19 infections in the single digits, the Navajo Nation – a 71,000 square-kilometer (27,000-square-mile) expanse of the western US – reported 54 new cases of what's referred to locally as "Dikos Ntsaaígíí-19."
The Navajo Nation covers the corners of three different states. Google Maps
Growing Contribution<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM3NDY5Ny9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NjM4MTgyM30.IuQTKQs1stvYYKD6vaVTrqAyoBsUG0BhDvlhxsyKwPA/img.png?width=980" id="02a05" class="rm-shortcode" data-rm-shortcode-id="2841f82b1785df5d5ed7bf64d3bb882b" data-rm-shortcode-name="rebelmouse-image" />
World Economic Forum
- Black and Hispanic Americans Suffer Disproportionate Coronavirus ... ›
- Native American Tribes' Pandemic Response Is Hindered by ... ›
- Navajo Nation Has Highest Covid-19 Infection Rate in the U.S. ... ›
World Environment Day: A Time to Consider the Planet We’ll Return To, and Decide How to Care for It Going Forward
It's a different kind of World Environment Day this year. In prior years, it might have been enough to plant a tree, spend some extra time in the garden, or teach kids the importance of recycling. This year we have heavier tasks at hand. It's been months since we've been able to spend sufficient time outside, and as we lustfully watch the beauty of a new spring through our kitchen's glass windows, we have to decide how we'll interact with the natural world on our release, and how we can prevent, or be equipped to handle, future threats against our wellbeing.
Scuba divers around the world are holding their metaphorical breath to see if a coronavirus infection affects the ability to dive.
DAN medical experts explained the difference between normal lungs, on the left, and "very serious lungs caused by COVID-19," on the right. Matias Nochetto / Divers Alert Network (DAN)
- How the COVID-19 Coronavirus Attacks the Entire Body - EcoWatch ›
- What Does 'Recovered From Coronavirus' Mean? - EcoWatch ›
- Scuba Divers Make Face Masks out of Recycled Ocean Plastic ... ›