Changing wildlife in central Tokyo's Imperial Palace sends quiet warning

The Imperial Palace forest in central Tokyo, once a refuge for wildlife, now serves as a silent indicator of changing environmental conditions. A 30-year study of the forest, initiated by Emperor Emeritus Akihito, has reached a significant milestone. Researchers have documented 7,982 plant and animal species within the 115-hectare area, despite observing some organisms vanishing.

The forest, surrounded by moats and home to towering trees like 300-year-old chinquapin and sawtooth oaks, is an urban oasis teeming with biodiversity.

Yoshihito Ohmura, a researcher at the National Museum of Nature and Science, led the final phase of the survey, which ended in 2025. The extensive study covered plants, animals, algae, fungi, and bacteria. Among the discoveries were a new species of soft windflower, Anemone imperialis, and a previously unknown species of mite, Eotetranychus palatiensis.

Sayako Kuroda, Emperor Naruhito's younger sister and a research fellow at the Yamashina Institute for Ornithology, documented the presence of northern goshawks and owls breeding in the palace grounds, indicating a thriving ecological environment.

However, the survey also revealed troubling trends. The native Japanese tree frog has disappeared, replaced by bullfrogs and aggressive mosquitofish, both introduced species. The rare candleflame lichen, resilient to pollution, has nearly vanished from a trident maple tree. The arrival of the Ictinogomphus pertinax, a dragonfly whose range is shifting northward, may be linked to rising temperatures due to climate change.

The Imperial Palace, a green island in a concrete jungle, remains a vital urban refuge for wildlife. However, the observed changes serve as a quiet warning, urging us to recognize the evolving nature of our environment.