[Gravityloss]

A lot of the "forests" we have at least here are planted monocultures which are periodically completely cut down. Also known as "tree farms". All trees are the same age. Also the forest is full of ditches that makes it hard to pass for animals. The ecosystem and the species living there are quite different to real more natural forests. Most people have never even been to a multi century old forest anymore. Also we get invasions of pests like Diprion Pini etc. But yeah it looks green from a satellite or even airplane.

[Merg]

I am a forester and maybe I can chime in. From the point of view of CO2 assimilation the clear-cut or even better cut in small parts over the years forests are much better than those old-growth multicentury forests around the world. Actually old-growth forest will accumulate less CO2 than younger counterparts and may have ratio of realeased and accumulate CO2 being close to 1:1. Number of species at least in European or rather Polish forests are pretty large in both natural protected and normally used forests. Of course they are countries with worse forest conditions like for example Africa or Scandinavia, but still greener planet = better planet. It doesn't matter that much, why it is greener.

The general approach changes at least here. The largest difference is relatively smaller density of dead wood in the forests, which is important and still not fully understood habitat.

[Gravityloss]

At least this science survey concludes that old forests do accumulate carbon. https://www.nature.com/articles/nature07276

Also a lot of the forest mass that gets cut is used for "green energy" so it's worse than letting it stay in the forest. Basically in a periodically burnt (bioenergy) forest the carbon is kept in the atmosphere most of the time while in an old growth forest it's in the trunks all the time.