What’s Earth’s dominant species by mass?
You might have heard that all the ants in the world weigh as much combined as all the humans. That isn’t true. We outweigh ants 5 to 1. Termites might have us beat, though. Either way, it’s not really a fair comparison. There are thousands of species of ants and termites, and just one species of human.
But if we’re judging each species based on how much total mass they have – that is, by its “biomass” – who actually comes out on top? Turns out there are some surprising winners.
Antarctic Krill: 379 million tonnes
Let’s start with our division: animals. Humans are pretty close to the top for a single species, weighing in at about 350 million metric tons. The top-placing wild species is Antarctic krill, with a 2009 estimate placing them at 379 million metric tons. Each individual krill weighs only about 2 grams or 0.07 ounces, but their sheer population in the Southern Ocean puts them in a statistical dead heat with us – and keeps gigantic blue whales comfortably fed.
But both humans and krill lag behind the true winner for animals: cattle. Cattle are easily the top domesticated animal species, with about 650 million metric tons of biomass. Pigs are in second, at about 140 million metric tons – placing them behind humans and krill.
Cattle: 650 million tonnes
Unfortunately for cattle, animals are almost the lightest of all the kingdoms of life. The most comprehensive study, (Bar-On et. al 2018) measures the different kingdoms by their carbon mass specifically. Carbon is only a portion of an organism, so this method gives smaller numbers. But those numbers are more meaningful for, say, tracking the flow of food energy through the biosphere (think of eating a pound of watermelon versus a pound of steak). For example, the 650 million tons of cattle on Earth represent only 61 million tons of carbon.
Animals as a whole have 2 billion tons of carbon. That means we handily outclass viruses (0.2 billion tons) but are beaten by protists (4 billion), archaea (7 billion), fungi (12 billion), bacteria (70 billion) and especially plants (450 billion).
Most of the world’s bacteria live in aquifers and seafloor sediments, which are hard to study. It’s possible that one extremely dominant undersea bacteria species has the world’s highest biomass, but more likely the winner will be a plant.
So what plant has the most biomass in the world? The winner for animals was a domesticated species, so let’s start with domesticated plants.
The first species that might come to mind are the major cereal grains like rice, wheat, and corn (maize). Of these, maize has the largest annual harvest by mass, totaling 1.1 billion tons – nearly double the mass of cattle. But the true biggest crop isn’t a grain at all.
That honor goes to sugar cane, with the harvest topping 2 billion metric tons in 2023. So humanity harvests about 6 times our collective weight in sugar cane every year. Sugar cane is also a perennial, meaning that its root system persists between harvests. This means total mass of living sugar cane on average throughout the year is probably higher than an annual crop like maize.
Sugar cane: 2 billion tonnes
But there’s still one more subcategory to look at: wild plants. It’s time to take on the trees.
Trees seem to hold all the superlatives. The most massive individual organism comes from a tree species: Pando the clonal colony of aspen trees with interconnected roots which weighs 6,000 metric tons all on its own. But aspens are pretty rare. Is there a more common tree with more total mass as a species?
For that, we have to look to the largest forest in the world: the boreal forests that ring the arctic circle. In those forests, just 3 or 4 species can represent over half of the total mass of the forest. By contrast, tropical forests can require over a hundred species to reach the same mark.
Two candidates boreal trees came up in a search of the literature. One is the Black Spruce, Picea mariana, which is the most common tree in arctic Canada. According to Canada’s National Forest Inventory, over 11 billion tons of black spruce are growing in the country, and some grow in the USA as well.
Black Spruce: More than 11 billion tonnes
The other candidate is the Dahurian Larch, the most common tree in Russia. Russia’s forest inventory doesn’t have as detailed numbers by species, but larches as whole in Russia are about 35.6% of Russia’s forest land, and Russia has a total of 82.2 billion cubic meters of forest. From what I could find, there are 2 main species of larch in Russia: the Dahurian Larch in the East and the Siberian Larch in the west, and the Dahurian is the more common of the two so it must be at least 50% of the total. Calculating the numbers and using the density of larch wood, that gives 16.8 billion tons of larch in Russia, of which at least 8.4 billion tons (and possibly more) is Dahurian larch.
Dahurian Larch: At least 8.4 billion tonnes, maybe more
Living black spruce wood is about 51% carbon, meaning there’s nearly 3 times as much carbon in just that one species of tree as all animals combined. So humans may still control the world’s biosphere, but on at least this one metric the spruce and larch trees have a massive lead.
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