To Combat World Hunger, Protect Biodiversity

Bernhardt, J. R., & O’Connor, M. I. (2021). Aquatic biodiversity enhances multiple nutritional benefits to humans. Proceedings of the National Academy of Sciences118(15).

Variety is the spice of life – or if you are an ecologist you might say “biodiversity” is the spice of life. Biodiversity is used to describe how a wide variety of living things (plants, animals, etc.) are all part of a healthy, thriving system. In most cases, biodiversity actually makes the living things in an environment more resilient to changes and healthier overall. However, scientists have started focusing on a new benefit of biodiversity – a more nutritious diet for humans.

A display of a variety of fresh seafood. Photo by Petr Kratochvil.

Biodiversity – here tomorrow or gone today?

Although biodiversity is an essential part of a healthy ecosystem, some systems naturally have a wider variety of plants and animals than others. For example, rainforests and tropical reefs are some of the most diverse, and also most threatened, ecosystems in the world.

If biodiversity seems a bit nebulous, imagine it from a human perspective. In a thriving community of people, there are a variety of professions, passions, expertise, ages, and social spaces. In my neighborhood, we have a number of car mechanics, a few computer programmers, some bakers and cooks, some teachers, and some construction workers. Together, our cars get fixed, our computers work, our children get educated, and we have nice spaces to gather and commune together over a good meal. Life is good. But let’s say we remove the teachers, or the car mechanics, or even the cooks and bakers. My neighborhood would continue to exist, but our lives would not be as rich or as healthy, and our future would be much more tenuous. In the example of my neighborhood, people might move away, but in the wild, if an essential role is not filled, species die.

A coral reef in Panama, which is said to have one of the most diverse reef systems in the Caribbean. Photo by thinkpanama.

Yet as humans continue to shape the planet, this loss of biodiversity continues relentlessly. Through climate change, pollution, deforestation, overfishing, or the introduction of invasive species, humans have helped pushed several species to extinction, to the point where this period in time has been dubbed a sixth mass extinction event by scientists. As humans, we often think of ourselves as outside of what goes on in nature, but this loss is likely to change us in ways we haven’t expected, starting with nutrition.

“Eat your veggies” – why Mom won’t let you live on PB&J

There is a reason humans don’t just eat one kind of food – we need a variety of vitamins and minerals to have a healthy, functioning body. No one food is going to provide everything we need, which is why I can’t just eat the delicious apple turnovers at my bakery and parents spend so much time cajoling their children into eating their carrots. When the scientists in this study decided to explore the benefits of a diverse diet of seafood, it was therefore the micronutrients (vitamins, minerals, fatty acids) that they decided to focus on.

The researchers scoured through a database of nutrition in 801 aquatic species, and then looked at how the nutritional value of species complemented each other. They first looked at the minimum amount of seafood the average person would have to eat to get all the nutrients they need in a day. They also compared the total amount of the recommended daily nutrients that would be fulfilled if a person ate 100g of seafood. The scientists predicted that with a more diverse seafood diet, people would get more nutrients in each portion of seafood and would therefore need to eat less to meet their daily needs.

Their hypothesis turned out to be true – when the scientists looked at a seafood diet that included 10 randomly selected species as opposed to just one, the average person would fulfill their dietary needs faster. In fact, eating more species meant that people reached their needs in 100g of seafood more frequently than if they were eating fewer kinds of seafood.

Mercury is released from volcanoes and human pollution, then enters the food web where it is biomagnified into bigger fish. Since the mercury is stored in the tissue of the fish, larger predators accumulate mercury from the smaller fish they eat, meaning predators tend to have higher concentrations of heavy metals than smaller fish. Graphic made by Bretwood Higman from Ground Truth Trekking. To learn more about how mercury gets in seafood, click here.

The heavy (metal) news

The researchers were also concerned, however, that as people ate more kinds of seafood, they might be exposed to more heavy metals, namely methylmercury, cadmium, arsenic, and lead (you can read how methylmercury in particular makes its way into seafood at oceanbites here). They examined the concentrations of these metals in 353 seafood species, and then compared how much a person would consume if they ate 10 different species as opposed to one.

Once again, the scientists were right to be concerned. In their analysis, consuming a wider variety of species did increase the number of these metals that passed their upper tolerable limits. Shockingly, the researchers estimated that the average amount of methylmercury a person consumed could double if they ate 10 different seafood species instead of one. However, the increase in other metals was much more minor. Lead concentrations for people eating 10 seafood species only increased 10% compared to those eating just one, for example.

Does this mean we should restrict ourselves to one kind of seafood? Not necessarily. Species that had high concentrations of one heavy metal tended to have high concentrations of other heavy metals. Choosing tuna for your one seafood species, for example, would be much more detrimental than eating tuna, mussels, and squid. What it does mean, however, is that when considering expanding the seafood we eat, we may want to be more careful and strategic about not eating fish that would have similar tendencies for heavy metal uptake.

What this means

Today, many human populations around the world rely heavily on seafood, and there are many populations that are undernourished in vitamins, minerals, and fatty acids. Having a diverse range of healthy and robust seafood species could help feed these people in the future, but this won’t be possible if we continue to lose species. If we move toward a healthier planet, we can move toward healthier humans. We can take climate change seriously and adapt now, reduce pollution, and be thoughtful about how we fish the ocean. By taking these steps, we will help both the planet and ourselves.

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