Isahaya-shi

In the latest Population Census the population is about 134,000 (133,852 in 2020). What should be noted first here is that the sharp rise of more than forty-eight thousand, from the 95,182 of 2000 to the 144,034 of 2005, is not the result of people naturally increasing. It is due to the merger in 2005 of the former Isahaya City with five surrounding towns, and the step in the numbers reflects that merger.

Looking at the substance after the merger upon that, from the 144,034 of 2005 to the 133,852 of 2020, some ten thousand have been lost over fifteen years. Those under fifteen fell by over forty-four hundred, from 22,360 in 2005 to 17,924 in 2020. The share aged 65 and over rose from 17.1% in 2000 to 30.6% in 2020. The household-with-children share is a high 22.7%, the Childcare Waitlist has been zero in recent years, and the Fiscal Capacity Index was 0.59 in fiscal 2023. The figure of a junction town widened by the merger, gently losing population yet keeping the weight of households with children, comes out in the numbers. Why it takes this form cannot be read without going back to the past of sea, highway and reclamation.

The urban area of Isahaya stands upon the singular position of land ringed by three seas. This town touches the three seas of the Ariake Sea, Omura Bay and Tachibana Bay, and lies at the root of the land passage linking peninsula and mainland. The main highways linking the interior of Nagasaki Prefecture — the Nagasaki Road, the Shimabara Road, the Tara Road — have crossed in this land. Within Nagasaki Prefecture, with its intricate coastline, Isahaya has functioned as a junction where land traffic cannot help but gather. Because it is ringed by sea, the land roads gather here — that is this town’s foundation.

At that boundary of sea and land, another past is piled on. Reclamation. At Isahaya Bay, reclamation turning sea into land has been pressed forward since around the Kamakura period, and in modern times the large-scale state-run Isahaya Bay reclamation project (from 1989) was also carried out. By this, a wide plain rare within Nagasaki Prefecture, which is poor in flatland, was opened, and this reclaimed land became one of the prefecture’s leading granary districts. The work of turning sea into land added a base of agriculture to the junction town. The Honmyo River, running through the urban area, waters this plain.

What decided the present shape of the city was the Heisei merger. In 2005 the former Isahaya City merged with Tarami, Moriyama, Iimori, Takaki and Konagai Towns, and it widened into a broad city area facing three seas. Beginning as a highway junction ringed by three seas, opening a granary district with reclamation, and widened by the merger — this town’s form stands upon the past of sea, highway and reclamation.

What characterizes Isahaya is that, while gently losing population after the merger, it keeps the household-with-children share on the high side. The total population fell by some ten thousand over the fifteen years after the merger, but the household-with-children share of 22.7% is on the relatively high side among the many regional cities that lose population. The location of a traffic junction, caught between Nagasaki City and Omura and close to Nagasaki Airport, can be read as an expression of how it has tied young households here to some degree.

In living infrastructure too, this junction character works. Lying in a position that can commute to both Nagasaki City, the prefectural capital, and Omura, where the airport is, has given this town its character as a bedtown. On the other hand, those under fifteen fell by over forty-four hundred, and the aging rate rose by over thirteen points in twenty years. Even while keeping the weight of households with children, the fall of the absolute number of children and the aging certainly reach this town too. The Childcare Waitlist has moved at zero in recent years. The town that flourished as a junction of three seas and opened a granary district with reclamation now holds, in a city area widened by the merger, both a gentle fall and the keeping of the weight of households with children. The total population gently falls, the children fall, the weight of households with children is kept. A falling indicator and a kept indicator stand at once in this junction town caught between Nagasaki City and Omura.

In Isahaya, several functions drawn in by a position ringed by three seas are layered. One is the singularity of that position — ringed by three seas and lying at the root of the land passage linking peninsula and mainland. The main highways of Nagasaki Prefecture crossed in this land, and it still functions as a traffic junction of the center of the prefecture. Another is the plain opened by reclamation continuing from the Kamakura period, forming one of the few granary districts in Nagasaki Prefecture, which is poor in flatland. And the Honmyo River runs through and waters that plain.

Isahaya is a junction town where sea, highway and reclaimed land overlap. From a highway junction ringed by three seas, to a granary district opened by reclamation, and to a city of the center of the prefecture widened by the merger — this very position, where the land roads gather here precisely because it is ringed by sea, drew in the highway junction and the reclaimed plain. Upon the landform of three seas and the Honmyo River, the past of highway and reclamation is folded together.