Satoyama destruction and homogeneity as sources of environmental vulnerability in Tokyo

In Japan, there exists a unique kind of landscape known as Satoyama. These are not wild, untouched forests, nor are they purely agricultural fields. Instead, they are the gentle, rolling margins where foothills meet farmland, a place where human activity and nature have long coexisted in a delicate balance. For centuries, these areas have served as a vital buffer, supporting a rich variety of birds, insects, and plants while helping to regulate the local climate and water flow. However, as cities expand, these transitional zones are increasingly being paved over or fragmented. This shift matters deeply because the loss of these green spaces does more than just remove trees; it strips away a natural system that has historically kept urban areas cooler, wetter, and more resilient against extreme weather. When these landscapes disappear, the environment loses its ability to absorb shocks, leaving cities more vulnerable to heatwaves and floods.

A researcher named Setsuko Onoda, working at Iwate Prefectural University, has spent years observing how this destruction plays out in and around Tokyo. Her work focuses on a specific, troubling trend: the replacement of diverse, living landscapes with uniform, concrete-heavy developments. She argues that current planning practices are ignoring the long-term health of the environment in favor of short-term economic gain. To understand this, she uses a way of looking at the land that combines two perspectives. First, she looks at the "surface," which is the physical map of the land at a single moment, showing how much green space remains versus how much is covered by buildings or roads. Second, she looks at the "line," which represents the history of that land over time, tracking how temperature, humidity, and animal behavior have changed as the landscape was altered. By combining these two views, she reveals a story of environmental decline that project-by-project assessments often miss.

Onoda's investigation covers the semi-urban areas between Tokyo and the neighboring Kanagawa Prefecture. She examined aerial photographs spanning nearly fifty years, from 1976 to 2024. In the 1970s, these photos showed a balanced mix of forests, fields, and homes, a patchwork that supported a healthy ecosystem. By the 1990s and continuing into 2024, the images tell a different story. The green patches have shrunk dramatically, replaced by dense clusters of housing and vast expanses of concrete. This is not just a visual change; it has measurable physical consequences. Meteorological data from the region shows that since the 1990s, temperatures in Tokyo have risen while humidity has dropped. The removal of trees and the covering of soil with concrete have created a local climate that is hotter and drier, a condition that weakens the remaining vegetation and increases the risk of flooding during heavy rains.

The human decisions driving this change are often rooted in financial pressures rather than a genuine need for more housing. Japan's population is shrinking, and the country already has a surplus of empty homes, yet new construction continues to clear away the last remaining green spaces. A major driver is the inheritance tax system. When landowners pass away, their heirs often cannot afford the taxes on forest or agricultural land, so they sell the property to developers. These developers then subdivide the land into small, uniform lots, building houses with little to no garden space. The goal is purely economic profit, creating a landscape of "cookie-cutter" homes that rely heavily on electricity and air conditioning. This approach treats land as a commodity to be sold rather than a living system to be maintained. Onoda points out that this is a deviation from the original purpose of housing, which should be to provide shelter, not to generate maximum profit at the expense of the environment.

The impact of this homogenization is visible in the behavior of the animals that once called these places home. Onoda conducted seven years of fixed-point observations, watching how wildlife adapted to the loss of their habitat. One striking example involves the Japanese pygmy woodpecker. In the past, these birds would drum on the trunks of large, old trees to communicate and mark territory. When those trees were cut down to make way for new housing, the birds did not simply leave. Instead, they began drumming on metal utility poles. The metal makes a louder sound than wood, so the birds adapted to the new, artificial environment. Similarly, a common kestrel, a bird of prey, was observed moving from the Satoyama fields into the city center to hunt, a shift in behavior that had not been recorded before. These changes are not signs of resilience; they are signs of distress, indicating that the natural environment has been pushed so far that the animals must alter their fundamental behaviors to survive.

The study also highlights how small, seemingly harmless management choices contribute to the larger problem. In many urban parks and slopes, local governments and private landowners now use weed-control sheets—plastic or fabric mats covered with gravel—to stop grass from growing. This is done to save money on mowing and to address labor shortages. While these sheets might let some water through, they prevent the soil from holding moisture effectively and stop diverse plants from growing. The result is soil that dries out faster and contributes to the rising heat of the city. Onoda notes that the use of these sheets has increased significantly, with the adoption rate reaching 7.5% in 2026. This trend, combined with the removal of street trees and the construction of high-rise buildings, creates a feedback loop where the city becomes hotter and drier, making it more susceptible to environmental disasters.

A critical part of Onoda's argument is that current regulations are failing to protect the environment because they look at development projects one by one, rather than considering the region as a whole. A developer might get approval for a single project that meets the minimum legal requirement for green space, but when dozens of such projects are approved across a city, the total amount of green space disappears. The system lacks a mechanism to see the "big picture" or to account for the historical accumulation of damage. For instance, a large redevelopment project near the Meiji-Jingu Shrine involved cutting down over 1,000 trees that were more than 100 years old to make room for commercial facilities. Although citizens sued to stop the logging, the courts rejected the request, and the trees were removed. This legal and administrative framework prioritizes economic development over ecological stability, allowing the destruction of landscapes that have taken centuries to form.

The findings suggest that the current path of urban development in Tokyo is moving away from its original social and ecological goals. Instead of creating resilient communities that can withstand climate change, the trend is toward creating fragile, uniform environments that are vulnerable to heat and flooding. The loss of Satoyama and the homogenization of the urban landscape are not just aesthetic issues; they are threats to the safety and well-being of the people living there. Onoda proposes that to fix this, we need to change how we evaluate development. We need to look at the land as both a surface and a line, considering the long-term history of the area and the cumulative impact of every new building. This means reinstating stricter regulations on green spaces, reusing existing vacant homes instead of building new ones, and recognizing that the natural world is not a resource to be consumed but a foundation for life that must be preserved. The evidence shows that without a shift in purpose, from profit-driven expansion to ecological stewardship, the region will continue to lose its ability to protect itself from the growing challenges of a changing climate.