Tokyo, the capital of Japan is one of the largest cities of the world. The administrative area of the Tokyo Metropolitan government covers the 23 special wards of Tokyo to the east, 26 cities to the west (Tama) and two outlying island chains (Izu and Bonin). Despite Tokyo being relatively small in area, it has a rich biodiversity that requires conservation efforts. I review the current status of the natural environment and biota (especially, flora of vascular plants and mammalian fauna) and discuss perspectives of biodiversity in Tokyo. There are different types of ecosystems in Tokyo: urban, secondary forest and agriculture (Satoyama), and oceanic island ecosystems. Different types of landscape support different habitat specialists. In Tokyo, the total numbers of wild plant and mammal species were estimated to be 4323 and 51, respectively. On the Izu and Bonin islands, species richness is relatively low, but endemism is high. The four principal pressures directly driving biodiversity loss (habitat change, abandonment of agricultural landscape management, pollution and invasive alien species, and climate change) are either constant or increasing in intensity in Tokyo. Although nature conservation has had significant results in maintaining biodiversity in urban and agricultural landscapes, there may be an emerging problem of human wildlife conflict in urban area due to biodiversity conservation projects in Tokyo. On the oceanic islands of Tokyo, alien species still seriously threaten endemic species of some taxa despite eradiation efforts. In 2010, Japan hosted COP-10 to the Convention of Biological Diversity (CBD). The results of COP-10 have had great impacts on policy and practices for conserving and managing biodiversity in Japan. Considering nature to be mostly anthropogenically-influenced in Tokyo, promoting a public understanding of biodiversity is the key to drawing up an urban planning framework for the sustainable management of biodiversity.
