But if in France, stay below the 40ha limit to not have to deal with massive costs of having your forest to be managed with validated planning every X years etc. which makes it very hard to keep "wild" areas in it (even more paperwork!).
I read about that a while ago! To me it seems like good-intent at first that turned out a complete bureaucratic creep! My question is: Can we decide to "manage" the forest ourselves and be registered as an official "forest manager", draft a management plan, publish any outstanding paperwork, etc ? I'm not sure about which administrative body would enforce the planning and management (municipalities, ONF, ...)
I won't go above 40ha for any foreseeable future, so it's probably not an issue!
Trees are not evolving as fast as the speed we destroy our environment, we have no choices left and we need to help them by not letting the forest completely wild. You need a bit of control. This is the reasoning being this 40ha limit. Starting this limit, you need to do the control seriously.
Mostly, the problem isn't actually one of too-slow evolution, but even more basic: Forests often can't migrate fast enough to keep up with current rates of climactic zone movement.
Human intervention is pretty simple and effective, though: keep planting trees on the leading edge of the forest (usually poleward or upslope where the limit is temperature, away from the coast where the limit is precipitation)
Of course, there are ecosystems that don't have anywhere convenient to move to (arctic and alpine, for example), but most forests don't fall into that category.