Green cities could remove CO₂ from the atmosphere

This is true, but I don't think it's that big of a problem, by simple thought experiment:

Trees also don't exist in the long term, for the same reason. Once they die, they're not there.

Given that forests exist, I think that CO2 can actually be stored there.

A forest has more sequestered CO2 than a field, probably. Individual trees die and decompose but new trees replace them.

A single tree won't, but a forest (aka, a system of trees growing and dying, to be replaced by more trees), will sequester CO2 meaningfully better than an open field.

You're missing the forest for the trees, my dude.

Better than an open field yes. How long does it take to burn down a forest? The amount of carbon stored in a forest compared to what we're pumping out from under the ground which has formed over millions of years is laughable.

Find your own forest, my dude.

Then maybe we shall keep the man with an axe away from them.