[National Museum of Nature and Science] Cumulative Confirmed Biological Species in the Imperial Palace Reaches 7,982: Publication of Phase III Imperial Palace Biological Survey Results
The National Museum of Nature and Science published the results of the 'Imperial Palace Biological Survey (Phase III)', conducted from September 2021 to March 2026, and released the 'Imperial Palace Living Things Database'. Phase III confirmed 2,178 species, including a new species of cyanobacteria, bringing the total number of species confirmed in the Imperial Palace to 7,982 when combined with past surveys and literature.
📋 Article Processing Timeline
- 📰 Published: May 22, 2026 at 23:00
- 🔍 Collected: May 22, 2026 at 14:31
- 🤖 AI Analyzed: May 22, 2026 at 14:54 (22 min after Collected)
The National Museum of Nature and Science (Director: Makoto Manabe) has compiled the results of the 'Imperial Palace Biological Survey (Phase III)' conducted from September 2021 to March 2026 as part of its comprehensive research project, 'Research on the Transition of Biota in Urban Environments Over the Past 150 Years: Analysis of Specimens Collected in the City Center Focusing on the Imperial Palace'. The museum published the National Science Museum Monographs No. 53, 'Imperial Palace Biological Survey (Phase III): Plants, Fungi, Algae, Cyanobacteria', and No. 54, 'Imperial Palace Biological Survey (Phase III): Fauna', at the end of March 2026.
Furthermore, the 'Imperial Palace Living Things Database', which contains information on these biotas, is now open to the public. This press release highlights the main findings of the Phase III survey compiled in the reports, coinciding with the launch of the database.
In this study, alongside comprehensively assessing the biota of the Imperial Palace, researchers confirmed one new species of cyanobacteria, as well as 8 lichen species, 13 fungi species, and 2 parasitic helminths newly recorded in Japan. The survey also clarified the presence of alien and endangered species, and changes in distribution and flowering periods due to environmental shifts.
When adding the number of species confirmed in literature to the surveys and research conducted by the museum over the past 30 years from Phase I to Phase III, the cumulative number of organisms confirmed in the Imperial Palace reached 7,982 species. This record indicates an extremely high level of diversity for a large-scale green space in the city center. It has been revealed through continuous surveys by researchers in various fields, complementing the diverse natural environment of the Imperial Palace, which has been maintained with relatively minimal human impact.
The Imperial Palace is one of the few large-scale green spaces located in the center of Tokyo's highly urbanized environment. Under Emperor Showa's wish to keep it 'as natural as possible', the area has been managed with relatively little human alteration or disturbance since before the war. The Imperial Palace contains forests, grasslands, and stone walls, as well as water bodies such as moats, ponds, and streams, forming a diverse environment where terrestrial and aquatic areas are contiguous (Figures 1 and 2).
Figure 1. Flora survey environments in the Imperial Palace. A. Dokan Moat. B. Otaki Waterfall. C. Plum grove in Fukiage Gyoen. D. Stone wall near Hanzomon Gate. E. Evergreen broad-leaved forest near Upper Dokan Moat. F. Deciduous broad-leaved forest in Fukiage Gyoen. G. Inui Street. H. East Gardens (the yellow-flowered plant is the invasive Bidens pilosa).
Figure 2. Diverse fauna survey environments in the Imperial Palace. A. Insect survey environment 1 (Former riding ground ruins); B. Insect survey environment 2 (Otaki Waterfall); C. Insect survey environment 3 (Former pool); D. Insect survey environment 4 (Middle Dokan Moat); E. Tardigrade survey environment (collecting moss from the base of a large tree trunk); F. Fish survey environment (Inui Moat).
The Imperial Palace Biological Survey began prompted by the wishes of Emperor Emeritus, who hoped that 'an accurate record of the living things in the Imperial Palace should be kept to understand subsequent secular changes'. In response, the National Museum of Nature and Science conducted a detailed biological survey (Phase I) over five years starting in 1996 (Heisei 8), and the results were compiled in December 2000 (Heisei 12). The follow-up survey results on fauna were published in March 2006 (Heisei 18), and the results of the Phase II survey, which began in May 2009, were published in March 2014 (Heisei 26). By the end of the Phase II survey, 5,903 species (1,616 flora species, 4,287 fauna species) had been identified (Note: Taxonomic groups such as varieties and forms are conveniently referred to as 'species').
The Phase III survey, conducted in cooperation with the Imperial Household Agency, aimed to understand changes in the biota of the Imperial Palace associated with environmental changes, check the invasion status of alien species, and perform comparative analyses using DNA information. A total of 2,178 species were confirmed, including 619 flora species and 1,559 fauna species, which encompass new species, newly recorded species in Japan, and endangered species. Of these, 552 species were newly confirmed during the Phase III survey (including newly collected specimens and new identifications of unidentified stored specimens). Adding the number of species confirmed in the literature to the cumulative number confirmed since Phase I, there are 2,637 flora species and 5,345 fauna species, bringing the total number of organisms confirmed in the Imperial Palace to 7,982. Additionally, various insights were gained, such as the detection of intraspecific lineages and characteristic community structures not found in other regions, and the detection of changes in seasonal activities and distributions of organisms due to urban warming.
In the botanical field, the survey was divided into 10 groups: alien plants, aquatic plants, bryophytes, macroalgae, microalgae, lichens, fungi, imperfect fungi, pollination networks, and flowering survey analysis. Surveys were conducted targeting diverse terrestrial and aquatic environments in the Imperial Palace, including forests, grasslands, stone walls, moats, ponds, and streams. In this survey, 17 alien plant species, 37 aquatic vascular plant species, 117 bryophyte species, 9 macroalgae species, 56 microalgae species, 110 lichen-related species, and 277 fungi species were confirmed. Notably, a new species of cyanobacteria, Oscillatoria imperialis (Figure 3), was described, alongside multiple species newly recorded in Japan, including 8 lichen species and 13 fungi species (including corticioid fungi, mucoralean fungi, and myxomycetes).
Furthermore, the 'Imperial Palace Living Things Database', which contains information on these biotas, is now open to the public. This press release highlights the main findings of the Phase III survey compiled in the reports, coinciding with the launch of the database.
In this study, alongside comprehensively assessing the biota of the Imperial Palace, researchers confirmed one new species of cyanobacteria, as well as 8 lichen species, 13 fungi species, and 2 parasitic helminths newly recorded in Japan. The survey also clarified the presence of alien and endangered species, and changes in distribution and flowering periods due to environmental shifts.
When adding the number of species confirmed in literature to the surveys and research conducted by the museum over the past 30 years from Phase I to Phase III, the cumulative number of organisms confirmed in the Imperial Palace reached 7,982 species. This record indicates an extremely high level of diversity for a large-scale green space in the city center. It has been revealed through continuous surveys by researchers in various fields, complementing the diverse natural environment of the Imperial Palace, which has been maintained with relatively minimal human impact.
The Imperial Palace is one of the few large-scale green spaces located in the center of Tokyo's highly urbanized environment. Under Emperor Showa's wish to keep it 'as natural as possible', the area has been managed with relatively little human alteration or disturbance since before the war. The Imperial Palace contains forests, grasslands, and stone walls, as well as water bodies such as moats, ponds, and streams, forming a diverse environment where terrestrial and aquatic areas are contiguous (Figures 1 and 2).
Figure 1. Flora survey environments in the Imperial Palace. A. Dokan Moat. B. Otaki Waterfall. C. Plum grove in Fukiage Gyoen. D. Stone wall near Hanzomon Gate. E. Evergreen broad-leaved forest near Upper Dokan Moat. F. Deciduous broad-leaved forest in Fukiage Gyoen. G. Inui Street. H. East Gardens (the yellow-flowered plant is the invasive Bidens pilosa).
Figure 2. Diverse fauna survey environments in the Imperial Palace. A. Insect survey environment 1 (Former riding ground ruins); B. Insect survey environment 2 (Otaki Waterfall); C. Insect survey environment 3 (Former pool); D. Insect survey environment 4 (Middle Dokan Moat); E. Tardigrade survey environment (collecting moss from the base of a large tree trunk); F. Fish survey environment (Inui Moat).
The Imperial Palace Biological Survey began prompted by the wishes of Emperor Emeritus, who hoped that 'an accurate record of the living things in the Imperial Palace should be kept to understand subsequent secular changes'. In response, the National Museum of Nature and Science conducted a detailed biological survey (Phase I) over five years starting in 1996 (Heisei 8), and the results were compiled in December 2000 (Heisei 12). The follow-up survey results on fauna were published in March 2006 (Heisei 18), and the results of the Phase II survey, which began in May 2009, were published in March 2014 (Heisei 26). By the end of the Phase II survey, 5,903 species (1,616 flora species, 4,287 fauna species) had been identified (Note: Taxonomic groups such as varieties and forms are conveniently referred to as 'species').
The Phase III survey, conducted in cooperation with the Imperial Household Agency, aimed to understand changes in the biota of the Imperial Palace associated with environmental changes, check the invasion status of alien species, and perform comparative analyses using DNA information. A total of 2,178 species were confirmed, including 619 flora species and 1,559 fauna species, which encompass new species, newly recorded species in Japan, and endangered species. Of these, 552 species were newly confirmed during the Phase III survey (including newly collected specimens and new identifications of unidentified stored specimens). Adding the number of species confirmed in the literature to the cumulative number confirmed since Phase I, there are 2,637 flora species and 5,345 fauna species, bringing the total number of organisms confirmed in the Imperial Palace to 7,982. Additionally, various insights were gained, such as the detection of intraspecific lineages and characteristic community structures not found in other regions, and the detection of changes in seasonal activities and distributions of organisms due to urban warming.
In the botanical field, the survey was divided into 10 groups: alien plants, aquatic plants, bryophytes, macroalgae, microalgae, lichens, fungi, imperfect fungi, pollination networks, and flowering survey analysis. Surveys were conducted targeting diverse terrestrial and aquatic environments in the Imperial Palace, including forests, grasslands, stone walls, moats, ponds, and streams. In this survey, 17 alien plant species, 37 aquatic vascular plant species, 117 bryophyte species, 9 macroalgae species, 56 microalgae species, 110 lichen-related species, and 277 fungi species were confirmed. Notably, a new species of cyanobacteria, Oscillatoria imperialis (Figure 3), was described, alongside multiple species newly recorded in Japan, including 8 lichen species and 13 fungi species (including corticioid fungi, mucoralean fungi, and myxomycetes).
FAQ
皇居生物相調査（第Ⅲ期）で新たに発見された新種は何ですか？
シアノバクテリアの新種であるオスキラトリア・インペリアリス（Oscillatoria imperialis）が新たに発見されました。
これまでの調査で皇居内で確認された生物は合計何種ですか？
第Ⅰ期から第Ⅲ期までの調査と文献記録を合わせると、累計7,982種（植物分野2,637種、動物相5,345種）が確認されています。
第Ⅲ期調査では何種類の生物が新たに確認されましたか？
第Ⅲ期調査では植物分野と動物相あわせて2,178種が確認され、そのうち552種が新たに確認された種です。
皇居生物相調査はいつ、どのようなきっかけで始まりましたか？
上皇陛下が「皇居内の生物について正確な記録を残し、経年変化を把握することが望ましい」と願われたことを発端として、1996年（平成8年）から第Ⅰ期調査が始まりました。
皇居の生物多様性が高い理由は何ですか？
昭和天皇の「できるだけ自然のままに」というご意向のもと、戦前より人為的改変が少なく管理されてきたことと、森林や水域など多様な環境が形成されているためです。