With the temperature 96 degrees in the shade, veterans of this concrete jungle braced themselves recently as they opened a door to an apartment building roof. But instead of confronting a wall of dry heat, they felt their faces cooled by moist air, carrying a light scent of soil and fresh grass. Tile by tile, workers were laying a new form of ultralight and ultracheap roof garden. With a low-maintenance variety of grass growing in four inches of vermiculite, a mineral substance often used in gardening, this carpet of cooling green weighed only 16 pounds per square foot. ”If a roof is rated to take people, which most are, it can easily take a roof garden,” Takaharu Yoshioka, environmental director of Greenich Garden, a landscape design company, said stepping onto the emerald lawn. ”Last year we did only 50 roof gardens. So far this year we have already had 200 orders.” The realization that Tokyo is becoming a vast ”heat island” is behind the boom in roof gardens. Here, centuries of gradual climate change are telescoping into decades. ”Over the last century, Tokyo temperatures have increased five times as fast as global warming,” said Takehiro Mikami, […]