OVERINDEXING

Humans comprise just 0.01% of the total weight of life on Earth, but have destroyed far more

If you’re the type of person who thinks about the expanse of the universe and starts to sweat, turn away now. If you’re the type who draws comfort from the insignificance of humanity, here’s a chart to keep at hand for whenever you’re struggling to fall asleep, and need something to soothe you into slumber.

A study published last week in PNAS attempted to take a biomass census of the entire Earth. It found that the entirety of life comprised some 550 gigatons of carbon (Gt C), and basically, it’s all plants.

The study broke down the planet’s life forms into a fairly rough set of categories. Some are at the kingdom level (animals, fungi, archaea, etc.) while others are more fine-toothed (like marine invertebrates, and livestock). Also, they included viruses, which are not actually living, but do behave like living things.

The results show that plants comprise about 450 GT C, bacteria account for 70 GT C, fungi make up 12 GT C, archaea (a type of single-cell organism) are 7 GT C, and protists (a group that includes algae) are 4 GT C.

What about humans? Well, all animals—land, sea, and air; vertebrate and non—make up 2 GT C. Humans are a measly 0.06 GT C, less than roundworms, mollusks, and pretty much everything else alive. Another way to see it: humans account for just 0.01% of carbon weight on Earth.

You might be wondering, “why carbon?” After all, it’s not what anyone uses to weigh things in the real world. The study authors say they thought through other options, but went with carbon mass because one, it’s independent of water content (so thus less variable) and, two, it’s what the literature in the past has used, for the most part. The researchers dug through that literature to find biomass samples from a number of different locations around the world, representing all sorts of environments. Then, they figured out the global distribution of these various environments, and used that to come up with an estimate for all of planet Earth.

So, of course, this is inexact. But it does offer a powerful perspective about our position on the planet. One other finding of this study worthy of additional pondering: The biomass of livestock far surpasses that of wild mammals; same goes for domesticated vs. wild birds. In fact, if you combine humans and livestock, it becomes a group that outweighs all other non-fish vertebrates combined. In other words, we make up just a tiny portion of life on Earth, but we’re punching way above our weight. And not in a good way.

The study estimates that since human civilization began, the planet has lost 83% of its wild mammals, 80% of its marine mammals, 50% of plant life, and 15% of its fish. Welcome to the anthropocene.

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