How is one to do that with a large population?
Instead of a few gianormous communities, make smaller communities, more easily connected via mass transit such as light rail.
Already and for always, large cities have divided themselves into neighborhoods. It's just too impossible to know or feel connected to a million people or more. That's for starters. But also: people absolutely require connection to nature, to sunlight and moonlight and starlight, to seasons, to plants and animals and growing seasons. They also need to be closer to where food is produced--and that's healthier and greener for everyone....
Since we are stuck with large communities,
No, we are not. Besides, what you are talking about is large cities which is the antithesis of community.
one must ask how to create an approximation of small communities in them.
Or have small, interconnected communities.
A good way, it seems, is to build casual meeting areas, like benches on city streets. Some place where people can feel welcome to stay as long as they want, without being pushed out after a few minutes of (say) eating what they bought in a nearby café.
Beaches on city streets? Sure because everybody lives on a coast and the ocean levels aren't rising and there's no such thing as skin cancer or water pollution....
We have city parks. Some cities do it better than other cities. Some communities do it better than other communities. Some communities are simply built in such a way that all the 'extra' green spaces are maintained as lovely parklike settings, with plants and wildlife and a bench or two or even water fountains and bike paths. You don't have to be a large city to do that.
High density has the additional virtue of consuming less land than low density. It can also mean shorter commutes and better support for mass transit. So high density is environmentally good in those ways. I think that some environmentalists seem to have romantic notions of living on a farm, but there isn't enough land for everybody to live in a farm-sized estate.
High density means high concentration of impermeable surfaces, the need to transport things like: food long distances and removing people from nature. It also means a higher concentration of air pollution, light pollution, sound pollution, pollution in general and higher stress for individual humans living in those conditions.
I grew up in farm country, with family who ran farms back when it was not very profitable to do so. I know that it is not 'romantic' an enterprise at all. Nor is that what I am suggesting. What I am suggesting is that instead of massive urban areas surrounded by massive urban sprawl where quite a number of people don't actually recognize cows (sounds stupid but trust me: I've had to point out to more than one urbanite what an actual cow in a pasture was and I won't even go into the amount of time and energy I've spent explaining the difference between a cow and a steer and a bull or that while beef cattle produce milk, they are not raised to produce milk except for immediate offspring for short term and that specific breeds of cows are specifically bred and developed in order to produce breeds that are extremely prolific milk producers with a high level of butterfat and that the same was done with goats and sheep and (slightly different) hogs and chickens, etc.
But goddamit, everybody ought to know what a cow is and what a rooster is and what a chicken is and so on. And how to tell corn from soybeans from wheat from alphalpha in the fields. And how to tell if a tomato was allowed to ripen on a vine or grown to pack well to be shipped thousands of miles away. Or whether strawberries were likely to taste good because they are in season locally or whether they were shipped from CA or FL.
And there absolutely need to be wild spaces, buffers of undeveloped land in addition to wetlands and deserts and forests and beaches, etc.
