I really can't stand the way the word "sustainable" is used. On a sufficiently short timescale, everything is sustainable. On a sufficiently long timescale, nothing is sustainable.
More importantly, talking about sustainability only makes sense if we're not planning on any technological improvements. For instance, burning fossil fuels for energy obviously is only sustainable on a decades-to-centuries timescale, but that doesn't mean we need to stop; the question is whether it will keep us going for long enough to develop good alternatives.
Cars, on the other hand, aren't intrinsically unsustainable on a thousands-of-years timescale provided that they're powered sensibly.
"For instance, burning fossil fuels for energy obviously is only sustainable on a decades-to-centuries timescale, but that doesn't mean we need to stop; the question is whether it will keep us going for long enough to develop good alternatives."
That only applies from the peak oil perspective. From a global warming perspective, fossil fuels might have been unsustainable yesterday.
Yes, but the implicit timescale in these discussions is something near the expected lifetime for the children of those now living. On that timescale, most of us had better change something soon.
I don't think talking about green communities ignores technological advance. Rather, what's changed is the angle of technological attack. Green communities are an interesting experiment. Most of us work on taking the technology used by most of the world, and gradually reducing its sustainability and environmental footprint.
By contrast, zero carbon communities start with net zero carbon output to the environment and hope that they can expand from there to be economical and capable of sufficient densities.
That's true to some degree. However, much of our infrastructure are designed for 1000 year timescales but rely on technologies with far shorter timescales.
There are plenty of alternatives to powering our cars, but none currently (and none on the horizon either) that are as good (cost effective) as petroleum. The cost-benefit analysis will be changing, but we won't be able to adapt because our communities rely on cheap fuel. People will have the unenviable choice of paying an arm and a leg commuting, or letting their exurban communities (and the massive investment they represent) fall back into farm land.
Y'know, suburban and exurban communities are a conundrum: They bear a lot of the blame for the incipient energy crash, but they may be one of the average joe's best assets in surviving it. It's similar to the systemic inefficiencies in the Soviet system allowed an industrial buffer during their collapse (ref. Dmitri Orlov's essays). This inefficiency will let people convert that half acre of useless lawn into a garden bearing a good percentage of the food a family needs, the same way durable goods piled up in warehouses because of the Soviets' command-directed economy could be used and traded by those with access. Turn the local park into less-intensively-improved land growing staple cereals, and you've gone most of the way converting a suburb to a village that can at least subsist at a 17th century level.
In six years .... not terribly different. Though we can look at current technology thats up and coming and place bets that by this time such will be popular.
Look at Facebook, it has been around since 04 and four years later we are now just seeing the early majority hop on board. Adoption takes time and bureaucracies slow new and better tech down. i.e. alternative energy and telecommunications
More importantly, talking about sustainability only makes sense if we're not planning on any technological improvements. For instance, burning fossil fuels for energy obviously is only sustainable on a decades-to-centuries timescale, but that doesn't mean we need to stop; the question is whether it will keep us going for long enough to develop good alternatives.
Cars, on the other hand, aren't intrinsically unsustainable on a thousands-of-years timescale provided that they're powered sensibly.