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A map of the median human trophic level between 2005 and 2009. Darker-coloured areas sit in higher trophic levels. Image: PNAS.

The first-ever calculation of human trophic level (HTL), a measure of what and how much of a specific food people eat, “challenges the perception of humans as top predators,” according to a new study.

In reality, humans share a trophic level with other omnivores, particularly anchovies and pigs.

The study also shows that humans diets are changing: Some countries are becoming more carnivorous, while others are incorporating more plants in their diets.

The findings were detailed this week in the Proceedings of the National Academy of Sciences.

Trophic levels are used to describe where species fall in the food chain. The levels range from 1 to 5.

Primary producers, like plants or phytoplankton, are defined as trophic level 1 because they make their own food and generally don’t eat anything else (unless you count sunlight and oxygen).

Herbivores, like cows, are at level 2 because they eat plants. Carnivorous apex predators, like polar bears or killer whales, represent trophic levels that go up to 5.5.

So what is our position in the food web?

In 2009, the median global human trophic level was a paltry 2.21.

To estimate human trophic level, researchers used food supply data for 176 countries from 1961 to 2009 provided by the Food and Agricultural Organisation. Although humans can’t be considered apex predators, the global human trophic has increased by 3 per cent since 1961.

This is mainly due to the fat that humans are eating more fat and meat in general, and not because we are eating animals in higher trophic levels. (We are actually eating fish that occupy lower trophic levels since fishermen are catching fewer of the large marine predators).

Although countries included in the study have diverse diets, the researchers identified five major groups with similar eating patterns, shown in the map below.

Image: PNAS

• Group 1 (low and stable HTLs): This includes the majority of sub-Saharan countries and most of Southeast Asia, which have mostly plant-based diets that aren’t adding more meat.
• Group 2 (low and increasing HTLs): This represents several countries throughout Asia, Africa, and South America, including China and India that seem to be increasing their meat intake.
• Group 3 (higher HTLs than group 2 and increasing): This includes Central America, Brazil, Chile, Southern Europe, several African countries, and Japan. Like group 2, these places are eating more animals, a trend that reflects economic development and increased urbanization.
• Group 4 (High and decreasing after the 1990s): The United States belongs to this group, which is comprised of North America, Northern and Eastern Europe, Australia, and New Zealand.
• Group 5 (Highest overall HTLs and decreasing): This group includes Iceland, Scandinavia, Mongolia, and Mauritania. This is the only group where HTL has decreased as development factors like gross domestic product, life expectancy, and urbanization have increased.

The global increase in meat consumption is being driven by countries like India and China (group 1), where breakneck economic growth has given people the ability to add more meat to their diet, even though the overall amount of animal products eaten is still low compared to other regions of the world.

Image: PNAS

In contrast, places like Iceland, Scandinavia, and Mongolia, where traditional diets were high in meat, fish, and dairy products and low in vegetables, have experienced a decline in trophic level.

In Scandinavian countries, the shift toward a more plant-based diet is motivated by a greater awareness of health issues related to diets high in fat and meat. Government policies are pushing healthier diets. In Mongolia, a decrease in meat consumption is linked to a less nomadic lifestyle. A growing economy means they have access to a wider variety of food.

This graph shows the relationships between the human trophic level and Gross Domestic Product. Iceland and other Scandinavian countries, represented by the colour orange, have seen a decrease in trophic level due to government policies promoting healthier, plant-based diets. Image: PNAS

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