They might be planting "local, mainly broadleaf tree species", but the principle is still wrong. Why attempt to second guess what will work, when nature will do it better than we ever possibly could, saving a lot of labour, too. I'm sure the resulting woodland would be far more interesting.
Additionally the land may still have a purpose, such as for flood defense down stream, in which case engineering the habitat should absolutely take place.
Frankly the lack of trees in some areas of the UK (even rural areas, such as large parts of the Yorkshire dales/moors where I am from) would mean that forest regeneration would take far longer (100's of years longer, as we would have to wait multiple times for trees to mature before spreading seeds in the local area.
Another thing to take into account is the local wildlife. Due to having a very unhealthy amount of predators tree growth is hampered by large numbers of deer, rabbits and in many areas sheep, which roam in un-enclosed fashion. Mature trees do very well, but saplings just get grazed to oblivion.
So yes, please plant trees on this scale, but they do need to take their time, and do it right.
Re wildlife, yes they would need to be controlled if trees are to take root. Sheep and trees aren't natural bed fellows. I'm not a making a man vs nature argument here; support is necessary in all manner of ways, in some it means taking a hands-off approach.
As for lack of trees in some areas, that might be for a good reason. Not every bit of land is suitable for woodland. Where it doesn't take root, it's a hint. And where it takes root, I would ask how you come up with a figure of hundreds of years.
It will do the very opposite.
> Let's remember that plants migrate slowly!
You initially get lots of 'green stuff' if you plant it yourself. However, weeds are not as slow to take root as you might expect. If you've ever maintained a garden lawn without pesticides, you'll know that.
This plan smacks of "quick, quick lets make this work, to hell with the consequences of not thinking it through". Which is very much the mantra of today's world.
Haste makes waste.
“Helping nature” to make things move faster is a normal thing there. Other examples are reintroducing wolves in Yellowstone, and sinking old ships to help reefs develop. Would you be opposed to those, too?
> In densely populated areas, there is no nature; everything that happens or doesn’t happen gets decided by man.
Nonsense, and besides the point. In the densest of cities there is plenty of nature (beside us). And in any case this planned forest isn't being planted through the middle of manchester and leeds.
Even then, if an acre of urban land is left idle by man it will sprout all manner of weeds and, not before long, trees. Many a distopian sci-fi film will show this.