Have you ever wondered about how much of all the life on earth we humans make up?
It’s an interesting question with lots of different possible ways to answer it. One way is to think about the number of organisms: there are around 8 billion of us, as of 2024. What about the rest of the organisms?
Well, there are tens of trillions of bacteria living inside your body. Clearly, humans are vastly outnumbered by bacteria and archaea, collectively the most numerous microorganisms on Earth. To count all the microorganisms, we would need a one followed by thirty zeros (a billion is a one followed by nine zeros).
Our population numbers are also dwarfed by insects, the most numerous multicellular organisms (one followed by eighteen zeros).
Maybe quantity isn’t what we’re looking for, though. After all, I weigh 155 pounds, give or take, and a housefly weighs around 12 milligrams. To get to 155 pounds, you would need over 5 million flies to make up one me.
Maybe weight (or mass, more specifically) is a better way to think about how much of Earth’s life is made up of humans.
This concept is called biomass. Ecologists use it to give us a useful number here, so we can compare how much bacteria there is, not how many bacteria there are.
On Earth, the overwhelming amount of biomass is contained in plants. Of the 550 billion tons of living beings, 450 billion of them are plants.
Trees make up the majority of the plant biomass. Think about all those trees out there, making up more than half of the planet’s living stuff. They’re all out there, processing air for us to breathe, just as are we for them.
Next up are bacteria, probably making up tens of billions of tons of mass. Fungi follow up with somewhat less biomass than bacteria, and way, way less than plants.
Animals make up about 2 billion tons, and mammals make up around 10% of this.
Here’s where things might cause you to raise an eyebrow: human beings and the animals we’ve domesticated make up 80% of the mammalian biomass.
It’s true that we’re only talking about one particular corner of all biomass on the planet, but nevertheless, this really gave me pause when I considered how much of an impact on “the top of the food chain” we’ve had.
Regardless of your personal takeaways here, I wanted to at least present the concept of a different way to “count” life. Leaving the doorway to the absurd slightly ajar is my favorite approach, to think about things from a different point of view whenever possible.
What are some unusual ways you’ve learned to “count” things? Did you know much about biomass before today?
I love stuff like this!
Not to sound like a broken record, but one of my favorite Tim Urban posts is the "7.3 Billion People, One Building" (https://waitbutwhy.com/2015/03/7-3-billion-people-one-building.html), where he makes the case that we could fit the entire population of the world into a single fictional building on Manhattan.
It also has a few other comparisons that always make people do a double-take when you mention them, like the fact that if you put people next to each other shoulder to shoulder, we could all fit inside one of the world's smallest islands.
It's so hard to wrap our heads around it, given how busy and crowded some cities feel. And yet...
"To get to 155 pounds, you would need over 5 million flies to make up one me."
I'm glad to hear that human beings add up to about 5 million flies, give or take. I wonder if we are really worth it though. Do we each contribute 5 million times the value of a single fly? Some people don't for sure.