Is that electricity worth a mountainside? — Mega-solar in the hills, and the cost the map reveals

We recently added a layer called "Solar PV facilities (FIT-certified)" to MAPRISE. Based on the business-plan certification information published by Japan's Ministry of Economy, Trade and Industry (METI), it lets you overlay roughly 68,000 facilities across the seven Kyushu prefectures on the map, color-coded by generating capacity. From small ground-mounted arrays tucked into a corner of a property to large-scale mega-solar plants that cover an entire mountain, they all line up on a single screen.

Once the data was in place, I found myself thinking hard about one question: what kind of land is each of these points actually sitting on? When I overlaid the colored dots with the forest and slope layers, clusters of orange and deep-red points emerged across the green hills — unnaturally orderly. They were facilities carved out of cleared forest.

In the shadow of the "righteousness" of renewable energy

Let me say this first: I have no wish to denounce solar power itself. I do not dispute that renewable energy is necessary as a response to climate change. Panels spreading quietly across rooftops and former factory sites strike me as reassuring, even.

What troubles me is how some of them are built. Since the feed-in tariff (FIT) scheme began in 2012, solar power has expanded rapidly. Guaranteed purchase prices drew investment, and when flat land and rooftops were not enough, some plants were built on land created by felling forests and cutting into mountain slopes.

Forests do work we rarely stop to notice: they retain water. Trees and soil store rainwater, let it seep slowly into the ground, and hold back sediment; tree roots bind the slope together. What happens to that function when you cut down the forest, shave off the surface, and replace it all with a sheet of panels?

In fact, what has been reported in news coverage is muddy runoff and sediment flowing from these graded sites, surges of surface water with nowhere to go during heavy rain, and the anxiety of residents living downstream. The 2021 debris flow caused by an embankment in Atami, Shizuoka, was one catalyst for a new law regulating earthworks (the Regulation of Residential Land Development and Specified Embankments Act), enacted the following year in 2022 and put into effect in May 2023. The forest-land development permit under the Forest Act was also revised for solar power, so that development of a smaller area now requires a permit. That regulation has been tightened after the fact says a great deal about what was happening on the ground.

It is not only the slopes. "Light pollution" — sunlight reflecting off panels into nearby homes and roads — has also been the subject of complaints reported in some areas. Strong reflected light arriving from an unexpected direction at dawn or dusk becomes a daily burden for those who live there. Lost mountain ridgelines, fragmented animal habitats, clouded stream water: these costs, which rarely show up in the numbers, accumulate at the foot of each installation.

Destroying one part of nature for the sake of decarbonization?

Here is the contradiction that bothers me most. Renewable energy, meant to curb climate change, ends up — in order to be installed — cutting down the very forests that absorb carbon dioxide and protect us from disasters. Is generating that electricity really worth clearing a forest for?

I see this not as a problem with solar technology, but as a problem of siting — of where it is built. Rooftops, former factory sites, abandoned farmland, idle land already altered by human hands. There is even agrivoltaics, generating power while farming continues. Suitable land still remains in abundance; there should be no need to single out a rich forest. The fact that many local governments have already begun enacting ordinances to restrain installations in the hills is, I think, an expression of the same concern.

Which is exactly why it needs to be visible on a map

Before arguing for or against, what we should share first is the facts: which facility sits on what kind of land, and at what scale. Without seeing that, the debate dissolves into a clash of impressions.

The solar PV layer we added to MAPRISE is meant for exactly this. Try overlaying the certified-facility points with the layers for forests, slope, sediment-disaster warning zones, and rivers and watersheds. What each development — pushed forward under the banner of decarbonization — means for its region begins to take shape, quietly, on the map.

Note that positions on the map are approximate, based on published addresses, and may differ from the actual site. Even so, when a local government considers siting, when a financial institution evaluates the land behind a loan, and when each resident wants to confirm "what is happening to the mountains of my own town," this single map can be a starting point.

Is that electricity worth a mountainside? Each point layered onto the map asks that question — quietly, but unmistakably. We intend to keep building, on top of the map, the tools that let us face that question without looking away. For the ground risk that comes with land development, see embankment regulation zones and large-scale fill land; for the forest itself, see national forest GIS.

Source: location data for solar PV facilities is geocoded by MAPRISE from METI's Renewable Energy e-application (FIT certification data). This article is a discussion based on publicly available regulations and reporting, and does not refer to any specific operator or facility.