I’m not an expert at all but I know the plan is to keep most of HK as undeveloped woodland.

It’s one of the things that surprises visitors, despite being one of the most densely populated places on earth, 2/3rds of HK is a nature preserve and they plan to keep it that way.

Partly this is because nature is good and the city treasures the green spaces. Which is why you see those funny high rises with a square missing in the center, it’s not actually feng shui it’s because approval often requires that you don’t block the sun and views of the mountains.

But it’s also in part because the mountainous parts are not very suitable for building and they’re prone to mudslides so building up on them would be a bad idea.

It’s actually cheaper and easier to “reclaim” land from the sea which is where most new land comes from, but really it’s increasing density and building up that creates most new housing.