While you won't find any virgin forests in Tokyo's Edogawa Ward, you will find hedges -- nearly 30 km of them. Ironically, these strips of greenery were planted to combat the problem of the ward's dearth of other vegetation. These verdant stripes, bordering roads and buildings, are part of a ward-engineered greenery revival project.

"In the rush to develop, greenery was left behind," said Koichi Tamura of the ward's park construction division.

Like much of the metropolis, development has been the ward's dominant theme for the past century. But local governments gradually came to re-evaluate its importance after the economic boom of the 1960s.

"From around 1973 to 1978, the era of rapid economic growth and pollution began to gather attention and there was a realization that greenery needed to be increased," Tamura said.

Greenery makes up only 14 percent of downtown Tokyo, rising to 22 percent for the greater metropolitan area and nearly 60 percent when its lush western fringe is included.

In a bid to bring a bit of greenery to the concrete cityscape, Edogawa Ward devised a program in 1978 to subsidize the planting of hedges in place of concrete walls. After 23 years, 1,600 projects and 650 million yen in subsidies, the ward now has nearly 30 km of hedges surrounding its local homes and businesses, attesting to its efforts.

A few blocks from the ward office sits a prime example. A drab factory with corrugated iron walls is given a dash of color by the hedge surrounding it.

However, the ward is planning to revise its system this year, beginning with a cut to the current subsidy of 30,000 yen per meter of hedge, according to Tamura.

"We are also looking to focus on more individualized activities using ward land, mostly in parks, where groups or individuals can increase greenery by planting trees and plants and looking after them," he said.

The ward is not alone. The metropolitan government is also trying to boost urban greenery, with its newest policy twist entailing a vertical shift in thinking.

An ordinance obligating builders of structures more than 1000 sq. meters in area to plant vegetation on 20 percent of the structure's nonbuilding area has been revised to include a stipulation that companies also crown 20 percent of the building's roof area with greenery.

This marks a shift from greenery policies of the past, said Hideo Hara, of the metro government's environmental planning section. Originally, green projects were solely intended to enhance scenery and spruce up the dull urban cityscape. Not anymore.

"At first it was more of an aesthetic issue. But now other reasons, invisible to the eye, have become important. Increasing greenery is environmental policy," he said.

Looming big on the list of reasons to push greenery is the so-called heat-island effect. With large expanses of concrete and asphalt, urban areas absorb and radiate heat, much of which would be reflected by vegetation.

In the summer, scorching days regularly push the mercury in developed areas 3 to 4 degrees higher than in heavily vegetated enclaves, such as Meiji Shrine, Hara said.

One expert predicts that within 30 years, midsummer night temperatures in the heart of the metropolis could reach as high as 43 degrees.

"In recent years, the temperature has really jumped. The blame can't all be laid on the heat-island phenomenon, but the city is clearly getting hotter," Hara said.

Statistics bear him out. Nearly 30 days a year -- roughly double that of three decades ago -- are tropical nights, where the temperature does not sink below 25 degrees. The loss of vegetation is, somewhat surprisingly, a larger contributor to the heat-island effect than the concrete buildings that rise in its place.

"Nearly 80 percent of the heat-island phenomenon is caused by the loss of greenery, while only 20 percent comes from heat released from the city," Hara said. The increase in temperature has also altered the urban climate.

There are already documented increases in the severity of urban precipitation, said Hara, as a hotter city seems to give rise to more sudden bursts of rain, heightening the threat of urban flooding.

According to a plan released at the end of 2000, the metro government is aiming to boost greenery in its 23 wards by 3 percent over the next 15 years, in part to counter the effects of urban warming.

These moves have put the spotlight on roof gardens. Hara points out two buildings, both of which predate the government's current system, as shining examples of the types of roof gardens environment authorities hope will increasingly grace the Tokyo skyline.

St. Luke's International Hospital, near Chuo Ward's Tsukiji area, boasts an outdoor roof garden where patients, visitors and employees relax, find solace, and even smoke.

The nearly 2000-sq.-meter jungle, which sits six stories above the streets below, was constructed along with the building in 1992, said Katsuo Komuro, an architect at the hospital's planning office.

"For patients, just looking at greenery through a window isn't enough. We want them to experience it with the five senses as much as they can," he said.

"When they see the butterflies and dragonflies, they want to speed their recuperation and return to society," he added.

The head office of Dai Nippon Printing Co. in Shinjuku Ward has a roof garden replete with plum and cherry trees where employees often go to enjoy lunch and a snooze.

The Tokyo Metropolitan Park Association, a semipublic body started in 1985 with money from the metropolitan government and private contributions, currently offers assistance for greenery projects. The association has seen a rise in applications for roof garden subsidies, said Yoshie Doi, who is in charge of the subsidy program.

In fiscal 2000, the park association approved seven roof greenery subsidies, up from five the year before and zero just five years ago, Doi said.

Doi, who believes the rise has been encouraged in part by the metro ordinance, expects the trend to continue.

While the new program will no doubt encourage the greening of the city, Doi questions to what extent, because it is not everyday that buildings covering more than 1000 sq. meters are razed and rebuilt.

Programs based on local government initiatives have their limits.

"In the end, there really needs to be a change in consciousness, or greenery (in the cities) will not increase," she said.