There's a different opinion on lignin decomposing fungi:

Delayed fungal evolution did not cause the Paleozoic peak in coal production

https://www.pnas.org/content/113/9/2442

Thanks for linking the paper! I've thought the same delay was the case, but seems my knowledge is outdated by 4 years :).

Interesting -- thanks for linking. It's a pity though - I really liked the delay explanation!

Increasing total biomass permanently, e.g. reverting the loss in planetary forest cover, or growing the amount of soil, is a sink.

It's a small, shallow sink, making it effectively still a buffer. It isn't going to help much in addressing an exponentially growing flow. Especially that we won't be able to fully regrow forests anyway - there are more humans now, who need space to live and space for farming.

I thought it wasn't a sink because of methane?

I agree with your general comment, but since forests can be used for construction materials they come out a little better than merely being a buffer since the wood gets used in housing or manufacturing in places where steel or concrete would need to step in, both of which are much worse for the environment. If built with longevity in mind, wood framed houses can last around five hundred years, which is more than enough time for technological advancement to allow us to deal with excess carbon by then. Even if they're only designed as typical buildings are, it's still a good fifty years of buffer as wood in a house in addition to the buffer as they were growing as trees.

Forests are a real part of the solution.

I don't know how people are eliding "forests" from my statement about soil. Soil is important and poorly understood[0], which is ironic because it's where most carbon capture is happening now. Forests are nice, and everyone likes forests, but soil is pushing the needle in ways that a shitload of 500 year old houses ain't gonna[1].

[0]https://blogs.ei.columbia.edu/2017/11/13/where-is-all-that-c...

[1] https://www.pnas.org/content/115/46/11652

To be fair, you can never discuss forests in any sort of scientific manner without discussing soils. The two are fundamentally linked.

That said, regenerative agriculture is probably the single best carbon sequestration technology that we have given the raw amount of land we have depleted of its organic matter.

> Forests are a real part of the solution.

Yes, absolutely. I should have been more clear. It's really important that we plant trees, and that we pay attention to the type of tree we're planting and where we plant them.

If I was a fiction writer, I'd be writing a book about how humanity used gene drives to wipe out the ability to decompose lignin. Perhaps the original plan was to release the gene into the wild again after CO2 levels normalized, but somehow the gene was lost, and atmospheric CO2 is reaching dangerously low levels...

Static forests are a buffer. Expanding forests are a sink.

I had no idea. Where can I read more about this please?

I used a simplification.

Wikipedia has a bit more detail: https://en.wikipedia.org/wiki/Carboniferous#Rocks_and_coal

But a buffer helps you flatten the curve. Which is most important in slowing nonlinear processes.