The ward has decided to invest 6 million yen from this fiscal year to develop what it has nicknamed “Neri-shiba” (Nerima grass). It is promoting the turf as a way to cut costs and increase the green coverage ratio–the proportion of land area covered by greenery.
The ward hopes Neri-shiba can play a significant role in the greening of the ward, but some specialists say it could artificially pad the ward’s greenery projects.
The green coverage ratio refers to the percentage of a local government’s area that is covered with greenery as a result of greenery projects. According to the Land, Infrastructure, Transport and Tourism Ministry, there are no nationally unified standards for determining the percentages.
As some local governments include ponds and rivers in their green coverage ratios, each local government calculates its ratio independently. For the wards and municipalities in Tokyo, the metropolitan government’s guidelines compiled in 1988 are used to calculate the ratios. Only some areas, such as Setagaya and Suginami wards, top 20 percent.
Neri-shiba consists of 10-centimeter-long artificial blades with wider-than-normal gaps between the rows of the turf. These gaps are filled with sand about eight centimeters deep and seeded with natural grass seeds.
A turf installation firm said this type of ground cover has been used for soccer fields overseas, as it holds up well to being stepped on. But the company had never heard of it being used for greenification projects.
The ward is enthusiastic about introducing Neri-shiba because of rapid progress in residential land development in the ward, which is reducing greenery.
Nerima Ward’s current green coverage ratio is 25 percent, the highest among Tokyo’s 23 wards, but its rate has been gradually slipping.
Nerima Ward included a plan to cover the grounds of five public schools in the ward, 1.4 hectares in total, with natural turf in its five-year plan starting in fiscal 2007. However, it scrapped the idea as schools complained about the time required for cutting, fertilizing and doing other maintenance work.
The ward then decided to partially cover the grounds of 25 schools with natural turf, and has managed add a total of 1.1 hectares of greenery.
If things continue in this vein, the ward will likely not reach its goal of 30 percent green coverage by 2038.
An ‘out of the yard’ idea
Unlike natural turf, which requires regular maintenance such as watering and cutting, the ward claims that Neri-shiba is easy to maintain and costs can be kept low.
However, since the green coverage rate is calculated based on the amount of plants, artificial turf is not included in principle.
The ward hopes to find ways through research and development to have Neri-shiba counted as a plant, such as calculating how much carbon dioxide it can absorb.
Regarding this issue, an official in the planning section of the metropolitan government’s Natural Environment Division said, “Improving the green coverage ratio is intended to spread the idea, ‘Let’s protect nature.'”
The official said mixing artificial turf with natural grass is something they did not anticipate.
“Claiming it’s a plant is difficult,” the official said.
Same amount of work?
Since Neri-shiba uses artificial turf made of plastic, there are concerns it will cause temperatures to rise under the strong summer sun.
Experts say it remains to be seen how much it will reduce the so-called heat island phenomenon in urban areas, even when it is mixed with natural grass.
“It’s like making a garden with fake flowers. It looks green to human eyes, but it’s far from the original intent of ‘greenification,'” said an executive at a Tokyo greenery consulting firm.
Kenichiro Fujisaki, vice chairman of the Japanese Society of Turfgrass Science and a full-time instructor at Nihon University teaching landscape architecture, sees it differently.
“If the natural grass grows so much it covers the artificial turf, I don’t see a problem with including it in the green coverage ratio,” he said.
However, if the grass grew that much, regular maintenance, including cutting and fertilizing, would be necessary.
“Then it would not be so different from natural grass [in terms of costs, maintenance time and other factors],” Fujisaki said.
Filed under: 5.Climate Change & Carbon