Sekisui House, Ltd. (TOKYO:1928) has been pursuing the conservation of biodiversity since 2001 by creating green networks in urban residential districts under its Gohon no ki (“five trees”) indigenous landscaping concept. Together with the University of the Ryukyus1, the company has analyzed the outcome of the Gohon no ki Project that it has implemented with 1 million customer households2 over the space of 20 years, and has designed the world’s first mechanism for quantitatively evaluating urban biodiversity. It has published this qualitative evaluation mechanism today as a nature-positive methodology for promoting the conservation of biodiversity.
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Results of quantitative evaluation analysis (1) - The number of native tree species in each region—the foundation of regional biodiversity—has increased tenfold. (Graphic: Business Wire)
The Gohon no ki Project
Since the 1970s, incessant urban development has dramatically reduced the amount of habitat available for flora and fauna in our cities. Sekisui House launched its Gohon no ki Project in 2001 as an initiative to conserve biodiversity through the eco-friendly landscaping and greening of the gardens of its customers. Based on the concept of planting five locally native trees, three for birds and two for butterflies, the Gohon no ki Project proposes greening gardens and local communities with native tree species suited to the local climate and benevolent to birds, butterflies, and other local fauna. The project takes its lead from garden landscaping modeled on traditional Japanese satoyama (which translates roughly as “village woodland”).
In the 20 years from 2001 up to 2020, more than 17 million trees have been planted under the project. The company has also promoted urban greening throughout Japan by incorporating the Gohon no ki concept into its planning of green spaces in its condominium and community development initiatives.
Quantitative evaluation of biodiversity
Sekisui House has since 2019 been working with the Kubota Laboratory, Faculty of Science, University of the Ryukyus, and Think Nature Inc. to quantitatively evaluate the contribution of this network-type greening to urban biodiversity. Based on the Japan Biodiversity Mapping Project (J-BMP)3 managed and operated by Think Nature Inc., a company established by Professor Yasuhiro Kubota, the partners have analyzed the data on tree number, species, and location accumulated over the 20 years of the Sekisui House Gohon no ki Project to quantitatively evaluate the effectiveness of the project in conserving and restoring biodiversity.
This quantitative evaluation revealed the following benefits for biodiversity from planting native tree species in line with the Gohon no ki Project as opposed to planting conventional horticultural and exotic species in gardens in urban areas where biodiversity has declined significantly (Japan’s three major metropolitan areas).4
- The number of native tree species in each region—the foundation of regional biodiversity—has increased tenfold.
- The number of bird species that residential districts can attract has doubled.
- The number of butterfly species that residential districts can attract has increased fivefold.
- Biodiversity in the three metropolitan areas has recovered to 30% of the level of 1977 for which the first trustworthy biodiversity related data exists.
This is the world’s first mechanism for quantitatively evaluating urban biodiversity and its application to an actual case. The disclosure of numerical data enables biodiversity to be expressed in terms of financial value, thereby providing a means for visualizing private sector contribution to biodiversity.
In recent years, increasing efforts are being made to conserve biodiversity. In June of this year, the Taskforce on Nature-related Financial Disclosures (TNFD) was launched, and in October, the 15th Conference of the Parties to the Convention on Biological Diversity (COP15) was held. In Japan too, discussion has begun in earnest on other effective area-based conservation measures (OECMs) for enlisting the support of the private sector to drive urban greening.
In this societal context, Sekisui House is making its 20-year biodiversity conservation initiative available to the public as a nature-positive methodology. The Gohon no ki Project’s nature-positive methodology represents a means for expressing urban biodiversity. Sekisui House is making this methodology available to the general public with the aim of raising awareness and enabling its store of knowledge and expertise to be utilized by others to promote greening and contribute to the conservation of biodiversity.
Nature-positive methodology website
Based on joint review of available data, Sekisui House and its partners set the number of tree, bird, and butterfly species, diversity index, and number of individual trees, birds, and butterflies in 1977 as 100%, and using 2000, the year before the Gohon no ki Project was launched, as the base year, simulated change up to 2070 in Japan’s three largest metropolitan areas (Kanto, Kinki and Chukyo) that have suffered the greatest decline in biodiversity. This simulation indicated that planting native tree species that are likely to benefit local fauna (the Gohon no ki concept) compared to 2000, the year before the launch of the Gohon no ki Project, would enable biodiversity to recover to 37.4% of 1977 levels by 2030 (target year for conservation of biodiversity internationally), 40.9% by 2050, and 41.9% by 2070.
If the Gohon no ki concept of planting native trees were applied to 30% of all newly constructed properties in Japan moving forward, urban biodiversity is predicted to rise to 84.6% of 1977 levels. Sekisui House believes that this indicates that if the private sector works with the general public, the decline in biodiversity can be reversed to achieve the goal of post-2020 biodiversity recovery that is the theme of COP15, and that its Gohon no ki concept can contribute to this goal.
We've received comments of endorsement from the following people. For more details, please refer to the attached document or the original news release via your browser.
- Mr. Makoto Haraguchi, Fellow, MS & AD InterRisk Research Institute and Sustainability Section SVP for TNFD, MS & AD Insurance Group Holdings
- Mr. Teppei Dohke, Executive Secretary General of the Japan Committee for the International Union for Conservation of Nature
- Ms. Mariko Kawaguchi, Specially Appointed Professor, Rikkyo University / Executive Advisor to CEO, Fuji Oil Holdings Inc.
- Mr. Yasuhiro Kubota, Professor, Faculty of Science, University of the Ryukyus / Representative Director, Think Nature Inc.
1. This is joint research with the Kubota Laboratory, Faculty of Science, University of the Ryukyus.
2. Cumulative number of households built from February 2001 to January 2021 is 1,001,977.
3. Japan Biodiversity Mapping Project (J-BMP) website: https://biodiversity-map.thinknature-japan.com
4. Comparison of continuing to plant conventional garden tree species with planting tree species in line with the Gohon no ki concept over the 20 years from 2001 to 2020