Can buildings be more porous, more open to the vitality of the surrounding city? As with the creation of the great urban parks of the 19th century, designers today are rebalancing the relationship between architecture and nature, with the goal of increasing the quality of life, especially in urban settings.

Sometimes this means erasing boundaries between indoors and outdoors, buildings and environment. Instead of the man-made and the organic jockeying for position or dominance, they are sharing each other’s territory. And occasionally they seamlessly fuse, each transforming the other. This, after all, is the age of the rooftop farm and the outdoor conference room.

Whether any of these gestures will mitigate the pressing problems of global warming and rising sea levels is still unknown — the fix likely requires more than what one landscape architect calls “boutique wetlands.” But projects debuting this fall suggest that hard barriers between the designed environment and the natural one are softening — maybe for good.