Which Life Form REALLY Dominates Earth?

Greetings home planet and all hail our supreme Zorgdorg. Mission update: I have completed my biological analysis of this planet’s life forms. There’s a lot of something called “cows”. As well as “ants”. Glad our home planet doesn’t have those. WOW! So many. I have concluded this planet is actually run by small birds called “chickens”. They outnumber the humans 2 to 1. HAHAHAHAHA and these humans think they are in charge HAHAHA actually the humans do kill a lot of stuff. Wish me luck. More research to come. What would it look like if we, or aliens posing as YouTubers, took a census of all Earth’s life, put it on a scale… to see what dominates, and if we’re changing it? There are a lot of humans on Earth — about 7.6 billion, in fact. But there are actually way more chickens, 19 billion! And way way more fish – those estimates are in the trillions. We humans actually only make up one one-hundredth of one percent of all life on Earth, by mass.

That hasn’t stopped us from having a big-time impact though. Sure, we’ve altered the landscape which is actually visible from space, and we’ve literally moved mountains, but there’s also an impact that’s a bit harder to see: all the death. Since our species spread across the globe, we’ve trampled out 84% of animals and over half of all plant life. Sheesh, so what’s left? Counting individual animals is hard and boring and would take a really long time, so instead scientists often measure something called biomass, basically how much living mass there is in some group of species. We measure biomass in gigatons of carbon. This is helpful when you want to compare species of different sizes. For example, 3,100 mice have the same biomass as one human. Or 15,312 Humpback whales have the same biomass as your mom. <cue airhorns> REAL MATURE GUYS Scientists recently found our planet hosts a total of 550 gigatons of living carbon. So how does it stack up? Let’s start with animals.

Of all animals, mammals and birds only make up 8.5%. And among that, 60% is livestock, mostly cattle and pigs. Humans? We’re more than a third (36%) of all birds and mammals, but we’re only 3% of the animal tally. Arthropods — the insects, spiders, crustaceans and other things with exoskeletons — far outweigh any other animal group, making up 60% of the animal kingdom. I mean, the termites alone nearly outweigh all 7.6 billion of us humans! But altogether, animals are a tiny 0.3% of Earth’s living mass. Mushrooms and other fungi are six times more massive than all the animals. There’s actually a colony of mycelium — an underground fungus… fungi… fungusi — in Oregon that stretches 1,665 football fields in area. It’s considered the largest organism on Earth. However, even fungi and fun-gals are just a tiny fraction of biomass compared to another group, one that’s absolutely massive despite being mini. A typical bacterial cell is a tenth the size of your typical animal cell.

Yet together, bacteria are a whopping 35 times more massive than all animals put together. Bacteria make up most of the small world, but the other groups of microscopic critters each individually outweigh birds and mammals (0.3% of total B) on the biomass scale (archaea (1.3%), protists (0.7%), and viruses (0.04%)). But bacteria aren’t the biomass-masters. The true rulers of Earth’s biosphere? Plants. Our green friends make up a whopping ~83% of all biomass. This result surprised scientists, because we tend to think of bacteria playing the biggest role in Earth’s biosphere. But when you think about how heavy a tree is, and the fact that there’s 3 trillion trees on Earth, their top spot makes sense. But then you think about the fact that they did all that by eating air and… Although most of the Earth’s surface is covered by ocean, turns out most of life, 86%, lives on land. It might be a blue planet, but it’s a green biosphere.

And even more surprising, there’s almost 12 times more life deep below ground, mostly microbes, than there is in the ocean. So that’s how life on Earth measures up. Thing is, that tally used to look pretty different. Humans and our close relatives have only been around about 6 million years, but in that short time we’ve managed to decimate life on this planet. From 50,000 to 3,000 years ago, half of Earth’s large mammal species died out, due in part to human activity. Whaling alone decreased marine animal biomass fivefold since the 1700s. Things like deforestation, hunting, and destroying habitats have knocked down terrestrial animals by a factor of six since we showed up. And don’t even get me started on climate change. Actually, DO get me started… and go check out our new climate and environment channel called Hot Mess 🙂 Link in the description. Where were we? Humans have also added new life to the mix – the planet now hosts more livestock than wild animals.

To feed ourselves and our animals, we’ve permanently cultivated nearly 600,000 square miles. If you add in pastures and stuff, about 18.9 million square miles has been turned over to agriculture — and our livestock are hogging 68% of that. Human population growth is slowing, but it’s still going up. By 2050 we’ll have something like 9.7 billion people aboard spaceship Earth, and who knows what that additional human biomass will do to the planet. If we keep adding more cows and chickens and people, lions and tigers and bears might only exist in storybooks! Plants, bacteria, and chickens, though, will probably still be here.

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