Using Data to Build Forests That Last 100 Years

Forests cover roughly 70% of Japan’s land, yet many are increasingly left unmanaged. When forests become too dense, trees develop shallow roots and spindly trunks, and the ground cover that would otherwise absorb the impact of rainfall struggles to take hold. The result is a heightened risk of landslides and flooding that threatens local communities. This problem is particularly pronounced in planted forests, where human management is essential to keeping the ecosystem in balance.

The planted forests established during Japan's postwar reforestation drive are now reaching maturity, but the people who managed them are aging, and the next generation has often been left without even a basic idea of where the family land is located. As properties change hands through inheritance, more and more forest owners find themselves with no clear picture of what they own—a significant obstacle when it comes to tasks like thinning trees or verifying property boundaries.

Climate change adds another layer of urgency. Forests play a critical role as long-term stores of carbon, locking CO₂ into timber and soil, but overstocked forests are less efficient at photosynthesis and absorb less carbon as a result.

In recent years, forest visualization through data has emerged as a key approach to addressing challenges such as disaster risk, ownership issues, and declining carbon sequestration. By quantifying the location and condition of individual trees, the data can support decisions ranging from boundary identification and thinning management to estimating carbon sequestration.

Although aerial imagery and satellite data are already used, obtaining detailed information from within densely forested areas remains difficult. In response to growing calls to address forest-related challenges, DENSO has been working since 2019 to digitize conditions inside forests—an undertaking that requires technology capable of operating in demanding outdoor environments.

“Environmental changes, including climate change, are partly influenced by the automotive industry. As DENSO works to reduce CO₂ emissions in pursuit of a carbon-neutral society, we are also focusing on improving carbon sequestration through forest management in Japan.”
ーFujii

Naoki Fujii of DENSO’s Social Innovation Business Development Function Unit explains. The forest project, as it is known internally, began as an effort to explore the intersection of the automotive industry, climate change, and forests. The idea originated after a typhoon in 2016 damaged forests in Hokkaido that team member Takashi Imura had inherited from his ancestors.

The concept of using automotive sensing technology for forest measurement began as a volunteer-driven initiative following an internal new business contest in 2018. It has since developed into demonstration projects carried out in collaboration with various government agencies.

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DENSO has focused its efforts on generating data that accurately reflects conditions within forests at a level of precision required by customers. Looking ahead to autonomous measurement using future electric mobility, the company adopted lightweight camera-based sensing, enabling the creation of 3D data that includes color information. With color data, features such as ground markers and differences in vegetation—difficult to distinguish in monochrome—can be identified more intuitively.

“When we think about forest owners who are not familiar with working with data, it’s difficult for them to grasp conditions on site if the data lacks color. With color included, features such as stone walls that serve as boundary markers can be visually confirmed, and in some cases, people recall being told long ago, this is where the boundary is."
ーImura

Since its launch as a volunteer-driven initiative in 2019, the forest project has explored opportunities to collaborate with a wide range of stakeholders, including government bodies. In 2024, it was selected for an innovation program in Aichi Prefecture, and DENSO has conducted demonstration trials with Toyota City for many years.

This photo has been adapted from the following work:“Fresh Green Korankei,” Toyota City, licensed under the Creative Commons Attribution 4.0 International License
（https://creativecommons.org/licenses/by/4.0/deed.ja）

Toyota City's strong focus on forest management can be traced back to the Tokai heavy rains of September 2000. Numerous mountain disasters occurred in the upper reaches of the Yahagi River, and urban areas in the midstream region came close to being submerged. This experience led to the recognition that maintaining healthy planted forests in the upstream area is essential for the safety of communities in the mid- and downstream regions, a principle that has since become the foundation of the city’s forest policy.

Following the Heisei-era municipal mergers in 2005, Toyota City incorporated surrounding towns and villages, becoming a forest city in which forests cover approximately 68 percent of the municipal area. In response, the city established a dedicated Forestry Division and has since promoted policies that approach forests from the perspectives of disaster prevention and residents’ daily lives.

In 2007, based on the belief that forest creation is a hundred-year undertaking, the city formulated the Toyota City Forest Creation Ordinance and the Toyota City 100-Year Forest Creation Vision. For more than 20 years since then, the city has worked on forest management aimed at thinning overly dense artificial forests.

Tsuyoshi Koyama, Deputy Director of the Forestry Division in Toyota City’s Industry Department, explains the city’s approach:

“Many national and local governments emphasize sustaining forestry as an industry by selling timber. In contrast, our Forestry Division has placed the safety and security of residents at the center of our efforts. Even our thinning activities are carried out from a disaster-prevention perspective. Currently, we are working toward a goal of eliminating overly dense artificial forests by the end of fiscal 2032.”
ーKoyama

Advancing the thinning necessary for proper forest management requires the consent of forest owners. To obtain that consent, it is necessary to identify the owners, confirm boundaries for forest management, and present the current conditions using scientific data. In practice, this involves two key processes: surveying to clarify boundaries and forest assessments to determine whether thinning is required. For the city, however, both processes had long been a significant burden.

Traditional surveying methods relied on pairs of workers walking through forests using compasses and distance meters. Measuring a single point took about five minutes, and surveying one area required two to three weeks. Forest assessments were similarly time-consuming, often taking four days or more per area, with the work remaining largely analog and dependent on manual labor.

Takayuki Tanaka, who is responsible for forest development promotion in the Forestry Division of Toyota City’s Industry Department, reflects on the situation as follows:

“We have reached the point where compass readings can be recorded digitally, but the method itself has hardly changed since the time of Tadataka Ino, the father of Japanese cartography. That’s why we’ve long felt the need to digitize and streamline the entire process.”
ーTanaka

Confirming forest ownership is also far from simple. Trees grow over periods of around 60 years, meaning ownership often passes to the next generation after planting. Many current owners are elderly and unable to visit the site, while others have moved outside the city or even the prefecture and may not even be aware that they inherited forest land. Even when ten stakeholders are gathered to confirm the ownership of a single area, in reality, only two or three people may actually be able to enter the forest.

Against this backdrop, the demonstration experiments conducted with Toyota City were far from straightforward. One major challenge encountered early on was verifying data accuracy. Discrepancies emerged between the data produced by DENSO’s system and the existing records that Toyota City had relied on for many years.

After carefully examining the cause, it became clear that conventional compass-based surveying is highly susceptible to magnetic interference near artificial structures like those made of concrete, meaning that the comparison baseline itself had limitations. As a result, the team shifted its approach to verifying accuracy using locations that had already undergone public surveying under the Survey Act as reference benchmarks.

Through this process, it was confirmed that the discrepancy between the measured forest boundaries (land boundaries) and the actual boundaries fell well within the acceptable range. At the same time, the time required for surveying is expected to be significantly reduced, from the previous two to three weeks to just two to three days.

Through this process of trial and error, a sense of progress gradually began to emerge in the field.
Tsuyoshi Koyama, Deputy Director of the Forestry Division in Toyota City’s Industry Department, reflects on the collaboration with DENSO:

“One of the most significant aspects of working with DENSO was the speed of the cycle from request to improvement. There were many moments when we thought, ‘It's fixed already?’ or ‘They handled that too?’ It made us feel that we might actually be able to reach the stage of real implementation.”
ーKoyama

Fujii, meanwhile, reflects on the perspective he kept in mind during the technology development process:

“Each customer has an appropriate level of quality they require, and even if we achieve millimeter-level precision, that doesn’t necessarily mean the people working on site need it. In the forestry field, hands-on judgment of experienced practitioners is highly valued, and since this is a public infrastructure initiative led by local government, there are also cost constraints. With those factors in mind, we worked to identify where the day-to-day challenges intersect with the available technologies, maintaining close communication throughout the process.”
ーFujii

Changes are also emerging not only in surveying but in forest assessments as well. Using the generated 3D data, it is now possible to measure the number, location, and diameter of trees within a forest. As a result, decisions that once relied heavily on the experience and intuition of veteran workers are increasingly being supported by data.

“People involved in on-site logging have told us that being able to visualize forest conditions in advance through data makes it easier to plan the order in which trees should be felled. They can draw up plans on days when rain prevents them from entering the forest, allowing them to move quickly once the weather clears. We are beginning to see how this could lead to significant improvements in operational efficiency.”
— Imura

These initiatives in Toyota City are also drawing interest from other municipalities facing similar challenges. Across Japan, the importance of forest management is growing amid concerns such as increased bear sightingsーfrequently linked to poorly maintained forest edges—and the rising risk of forest fires.
The project is scheduled to move into the implementation phase starting in fiscal 2026. By widely sharing the results achieved in Toyota City, the initiative also aims to expand to other regions.

The data and expertise accumulated through demonstration experiments in Toyota City and other areas hold potential that extends beyond improving the efficiency of surveying and forest assessments. One promising application is the creation of carbon credits. Carbon credits quantify the amount of CO₂ absorbed and stored by forests and allow that value to be traded, enabling companies to offset their own emissions.

Issuing these credits requires information such as the area of the target site, details about the trees, and records of ownership. If the data required for applications can be obtained collectively from the accumulated forest data, the previously complex issuance process could be significantly streamlined. Joint research with the University of Tokyo is also being conducted with this potential in mind, aiming to enable the creation of carbon credits based on more quantitative and reliable data.

Forest data is also expected to play a role in responding to landslides and wildlife damage. By continuously recording and comparing changes in vegetation and soil conditions, such data could provide a basis for detecting rising disaster risks at an early stage and for understanding shifts in the habitats of wild animals such as bears. Although these applications remain at the conceptual stage, they are becoming increasingly realistic as the volume and precision of available data improve.

At the same time, the challenges facing forests cannot be solved by any single individual or company alone. Issues such as the aging of forest owners, labor shortages, institutional barriers, and the complexity of region-specific conditions require ongoing trial and error at each site. Addressing these challenges will require cooperation that develops both technology and practical operations. Local governments, forestry operators, research institutions, companies, and individuals with a strong sense of purpose all have roles to play. Forest visualization is the starting point, but significant potential remains for people from a wide range of backgrounds to work together.

“Forest-related challenges cannot be solved by DENSO alone. That is why we hope to connect with people who are interested in our efforts and who are willing to think about these issues together with us. By continuing our work steadily while also expanding the circle of collaborators, we hope to contribute to solving the challenges surrounding forests.”
ーImura

Note: In this article, “surveying” does not refer to public surveying as defined under the Survey Act.