Jingu Gaien redevelopment, Big Motor… Background of street trees in jeopardy across the country “Experts’ Surprising Views”

If you thought undergrounding power lines would allow them to grow and spread their branches…

Big Motor has been criticized for spraying herbicides at the base of street trees, causing them to die.

The Big Motor has been criticized for spraying herbicides at the base of roadside trees and letting them die.

Even in the smallest of planted areas, nature is at work and a variety of creatures live there. If you find beauty in a place where not a single weed grows and not even an ant can live, I doubt your sense of beauty. This is a problem that goes beyond management morals.

says Professor Nobuo Fujiwara of Osaka Public University’s Graduate School of Business.

It would be outrageous to let roadside trees, whose leaves turn red and yellow in autumn and delight the eyes of passersby, die. Now, however, the trees are in danger.

In order for roadside trees to grow, it is important to secure space both above and below ground. However, both above and below ground are now in a very difficult situation for roadside trees.

Street trees are usually planted in a concrete area called a planting basin. Underneath the concrete is soil. It would seem that the roots can grow as long as they want,

However, because of the tight confinement under the road, it is impossible for the roots to grow under the roadway.

If it is difficult to grow under the roadway, what about the sidewalks?

“Recently, they have been trying to build a common drainage system for electricity, water, gas, and other utilities. Even if you eliminate power lines and poles and secure a space for branches to grow above the ground, if the roots cannot grow, they will die. It’s both a pain and an itch.

When branches get in the way of power lines, they are cut down without mercy. Then, if the power lines are underground, the roots cannot grow. The “power mix method” was developed to deal with this harsh environment for roadside trees. The idea is to create a space for roots to grow by adjusting the soil under the pavement to a larger grain size and creating a gap. This is similar to the image of a square container filled with golf balls, where a space is created between the golf balls.

To an expert, it seems like throwing money away to cut down a tree that has grown so large.

One would think that since such a construction method is being considered, there would be a movement to take care of street trees, but apparently not.

The number of street trees increased when the city was built during the postwar reconstruction period. The street trees planted at that time have grown too large and are becoming a problem.

This is why a plan to replace the street trees is being proposed. In Sakai City, Osaka, a plan is under way to remove 6,000 street trees and plant 3,500 new ones, because the trees planted along a 45-kilometer stretch of city streets have grown too large.

The city is planning to remove 6,000 trees and plant 3,500 new ones. “For us tree experts, it seems like throwing money away to cut down trees that have grown too big. If they grow and spread their branches, they will provide shade and absorb carbon dioxide. And yet, they are going to be small trees.”

Currently, plans are afoot to cut down approximately 900 trees and plant 1,000 new ones at Meiji Jingu Gaien in Tokyo due to redevelopment of the aging baseball and rugby stadiums. The International Council on Monuments and Sites (ICOMOS), an advisory body to UNESCO (United Nations Educational, Scientific, and Cultural Organization), is in great opposition to this plan as “irreversible destruction of cultural heritage. The Tokyo Metropolitan Government has asked Mitsui Fudosan and other business operators to show concrete ways to preserve the trees, but what will happen?

According to Professor Fujiwara, roadside trees have various roles.

• On hot summer days, trees provide shade, making it more comfortable for passersby to move about.
• They reduce the heat island effect.
• They absorb carbon dioxide.
• They prevent exhaust gases and noise from entering residential areas along the street.
• They attract birds and other living creatures. Ginkgo trees contain a lot of water.

Come to think of it, ginkgo trees are also effective in preventing fires because of their high water content. The trees in Tokyo, Osaka, and Yokohama are all ginkgo trees. Is it for fire prevention that there are so many ginkgo trees in urban areas?

It is true that ginkgo trees are fire resistant. But if you are serious about fire prevention, you need to plant rows and rows of ginkgo trees without leaving space between them. The reason why there are so many rows of ginkgo trees is because Japanese people love the sight of them turning yellow in autumn.

The ginkgo was originally a Chinese tree that came to Japan in the Nara period (710-794) and was spread for use as a medicine. It is said that when Kokubunji temples were built throughout Japan, ginkgo trees were also distributed throughout the country.

The most important effect of ginkgo trees is to beautify the streetscape. The biggest effect is that they make the streets look more beautiful.

The carbon dioxide absorption and other effects can be evaluated in monetary terms, but the psychological effects are “priceless.

Many street trees are deciduous. This is because they provide shade in summer, and in winter, sunlight shines through the trees that have lost their leaves. However, these fallen leaves are a peculiar problem. Many municipalities are concerned about the cost of cleaning up fallen leaves and pruning trees, and when old trees die, weed prevention sheets are put over the planting area, and new trees are not planted.

So now we are doing research to see how effective street trees would be if they were valued at a monetary value.”

In the United States, an analysis program called “i-Tree Eco” has already been developed to evaluate the effects of trees in monetary terms.

However, in order to use this system, we need to measure tree height and trunk circumference, and we need data on how many trees are of what size, but we don’t have that data.

Moreover, even though this program allows for monetary evaluation of the effects of carbon fixation, air purification, and rainwater storage, it does not allow for monetary evaluation of how much effect the trees are having psychologically.

It is a relief to have greenery. I understand that it costs money to maintain them, but I would miss the street trees if they were to disappear for that reason. What should be done about it?

The most important thing is to make the residents love the trees. There are many wonderful street trees in Japan, such as the camphor tree in front of the prefectural office in Miyazaki, the zelkova trees along Jozenji Avenue in Sendai, and the ginkgo trees in Jingu Gaien Garden in Tokyo. The rows of Nanjamonja (Hitotsubatago) trees in Nagoya are also magnificent, with their bright white flowers in season. I think all municipalities are struggling with the cost of maintenance and management, but they are not thinking of cutting them down. In Sendai, if you cut down one zelkova tree, the residents get very angry.”

Will love save the street trees, too?

Nobuo Fujiwara is a professor in the Department of Green Space and Environmental Science, Graduate School of Agriculture, Osaka Public University. Landscape architect. Environmentalist. Formerly director of the Greening and Ecology Research Office at the National Institute for Land and Infrastructure Management, and parks supervisor at the Aichi Prefectural Construction Department before assuming his current position. Engaged in the development of environmental conservation technologies as well as greening-related technologies for urban parks and roadside trees. He has been involved in the construction of several national parks, including Michinoku Morino Kohan Park, Yodogawa River Park, Uminonakamichi Seaside Park, and Kiso San-river Park.