An animal's ranking on the food chain depends on where its meals place on the ladder. That puts plants on the bottom (they make all their food), polar bears on top and people somewhere between pigs and anchovies. Lisa Brown for NPR hide caption
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Lisa Brown for NPR
An animal's ranking on the food chain depends on where its meals place on the ladder. That puts plants on the bottom (they make all their food), polar bears on top and people somewhere between pigs and anchovies.
Lisa Brown for NPR
When it comes to making food yummy and pleasurable, humans clearly outshine their fellow animals on Earth. After all, you don't see rabbits caramelizing carrots or polar bears slow-roasting seal.
But in terms of the global food chain, hom*o sapiens are definitely not the head honchos.
The World's Food Chain
In the new study, ecologists specifically calculated human's trophic level — a number between 1 and about 5.5 that tells you how much energy it takes to make a species' food.
Plants and algae, which use energy from the sun to produce all their food, sit at the bottom of the food chain, with a trophic level of 1. Right above them are herbivores, such as rabbits, cows and deer, which have a trophic level of 2.
Next come the omnivores that eat a mixture of plants and herbivores. That's where humans rank, with a trophic level of 2.2. Above us are carnivores, such as foxes, that eat just herbivores. At the top of the scale are meat-eaters that don't have any predators themselves, such as polar bears and orca whales.
Instead, we sit somewhere between pigs and anchovies, scientists reported recently. That puts us right in the middle of the chain, with polar bears and orca whales occupying the highest position.
For the first time, ecologists have calculated exactly where humans rank on the food chain and how it's been changing over the past 50 years.
One trend is clear: Humans are becoming more carnivorous.
On average, people around the world get about 80 percent of their daily calories from fruits, vegetables and grains. The other 20 percent comes from meat, poultry and fish, scientists at the French Research Institute for Exploitation of the Sea in Sete found.
"We are closer to herbivore than carnivore," the study's lead author, Sylvain Bonhommeau, told Nature. "It changes the preconception of being top predator."
But the meat-to-plant ratio in our diet has been rising since about 1985, the scientists found. And it's China's and India's growing love of chicken and pigs that is primarily fueling the recent change.
"With economic growth, these countries are gaining the ability to support the human preference for high-meat diets," Bonhommeau and his colleagues wrote in Proceedings of the National Academy of Sciences.
To place humans on the world food network, the ecologists carefully analyzed the food supply for 176 countries from 1961 to 2009. They got the data from statistics kept by the Food and Agricultural Organization of the United Nations.
Diets — and thus rankings on the food chain — varied widely from country to country. For instance, in parts of Africa and Southeast Asia, people eat still primarily a vegetarian diet, with up to 96 percent of their food coming from plants. At the other extreme, diets in Iceland, Mongolia and Sweden are about 50 percent meat and fish.
Not surprisingly, the U.S. ranked closer to the meat-loving countries than the plant-lovers. But Americans' location on the global food chain has actually dropped a small amount since 1961 — perhaps because we've finally started cutting down on those burgers and steaks.
