We’re becoming more and more carnivorous

In the last 50 years, the amount of meat in the human diet has increased massively, especially with the contribution of China and India. As a species we are predominantly herbivores, but for how long?

The human race is becoming more and more carnivorous, at a rate which threatens to be environmentally unsustainable. However, in the food chain we are closer to herbivores than we are to pure carnivores, as explained by French researchers headed by Sylvain Bonhommeau in the study published in Proceedings of the National Academy of Sciences. This study has examined Food and Agriculture Organisation (FAO) data on the consumption of 102 different types of food (everything from meat to dairy products to vegetables) in 176 countries from 1961 to 2009. For the first time, the data was then used to work out the trophic level of our species. This concept is used in ecology to describe the position of an organism in the food chain. Never before was it applied to humans. Trophic levels range from 1 to 5: these levels represent the number of steps that solar energy (the source of all energy on our planet) before it is consumed by an organism. Plants are at trophic level 1, as they use solar energy directly through photosynthesis. Herbivores – which eat plants – are at level 2, predators that eat herbivores are at 3, predators that eat other carnivores at 4, and superpredators (which have no predators) are at level 5. At level 5, together with noble predators such as lions, we also find the humble fungi, which decomposes all animals (including lions) and closes the circle.

If you’ve stopped following, this biology videolesson on trophic levels explains things clearly

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As many carnivores also eat plants, and some plants are also carnivores, boundaries are not set in stone. Consequently, trophic levels are not always represented by whole values: an animal can have a trophic level of 2.9 if, for example, it mostly eats meat but also the occasional vegetable – basically, if it’s an omnivore, just like us. A trophic level of 2.5 means that meat constitutes half the diet of that organism.

Researchers have calculated that in the last 50 years the trophic level of humans has gone from 2.15 to 2.21: a 3% increase. This may not seem much, but on a global scale it equates to a massive increase in meat consumption. This increase, as clearly shown by this graph, is caused mostly by China and India.

In the rest of the world, trophic levels of humans have stayed more or less identical, but in these two countries – which half a century ago were almost completely vegetarian – it has risen sharply, and today is now just below the world average.

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Trophic level of humans, 1960-2010

In the meantime, other countries which are historically carnivorous or large consumers of fish and dairy (such as Iceland, Mongolia and Mauritania) have varied their diets and therefore lowered their trophic levels, but the difference is negligible compared with these two countries. Iceland, for example, has a trophic level of 2.57 (which means its people’s diet is half composed of meat, fish and dairy), but as recently as 1974 it was 2.76 (almost a pure carnivore).

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Average trophic levels in different countries according to 2009 data.

The darker the colour, the higher the percentage of meat and fish in the diet.

Our trophic level of below 3 shows we are still mainly an herbivorous species, but this is rapidly changing. How we change and by how much are just two of the big questions on future food security and sustainability of our food production system. Here we ask if there are better alternatives for us carnivores than the consumption of beef, which we seem to love so much. In this article, Jonathan Foley points out that global evolution in the ‘carnivorous’ direction creates the risk of a food and environmental crisis. As we can imagine, this will be one of the main topics at Expo 2015.

As for our place in the planet’s food chain, even if we shouldn’t fear being eaten by anyone, we’re still very far from being superpredators, which corresponds to level 5 –awarded to only a few animals such as lions, crocodiles, sharks and killer whales. Researchers explain that our 2.21 puts us roughly on the same level as pigs and anchovies.

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