I'm a huge fan of Ron Milo's work and delight to see it being discussed, but putting it like this risks misinterpretation https://twitter.com/RobGMacfarlane/status/1336733051754319875

Put like this, anchoring assumptions make it easy to assume that the "total biomass of marine life & land animals" and "total global biomass" might be similar sorts of thing. As the paper shows, they are not.

"Total biomass of marine life & land animals" is, as per the paper, less than half of 1% of "total global biomass"
The total amount of plastic produced is, similarly, very small compared to total global biomass.

The vast preponderance of the human-made mass is concrete and aggregate; plastic is a very small fraction of it.

Most of the human made biomass is stone. And by stone standards it is really not very much at all. I imagine there are many mountains which weigh more than a trillion tonnes.

The truly amazing thing about that is that the Earth's total biomass is so small, it seems to me. With so little life on it the earth seems so alive.

None of this is to say that humans are not a massive factor in the world, and damaging to much of what is taken to be natural. The fact that the world's plastics weigh about 1% of what its plants do is chilling.

But I am not sure that mass is the most useful basis of comparison, especially when you compare the mass of inanimate stuff made by humans with the mass of animate stuff in the world (ie biomass)

If you compare inanimate stuff made by humans with inanimate stuff made by non-humans, things look entirely different.

The atmosphere, for example, weighs more than a thousand times as much as the Earth's biomass. But the molecular nitrogen and oxygen in it is almost entirely biogenic.

The weight of stuff made by non-human life thus weighs down on you with a pressure of about ten tonnes per square metre.

And that's before you get to biogenic rocks, which doubtless increase the made-by-non-humans side of things many more thousands-fold.

The mass of what humans have done in a century is large; it compares with the mass of all life on earth. But the mass of what all life on earth has done over 100m years is, I would hazard, at least a million times greater.

Again, this is not in any way to belittle the importance of the damage humans do to the environment. But it is good to put it in context.