Extinction risk status by habitat type

Insights from Japan’s Red Lists (1997–2025) and changes in habitat area

Abstract

Clarifying extinction risks across habitat types is essential for enhancing the effectiveness of spatial planning for biodiversity conservation. This study analysed vascular plant species listed in the Japanese Ministry of the Environment Red Lists of 1997, 2007, 2020, and 2025. For each habitat type, we examined (1) the number of threatened species, (2) the proportion of species in higher red list categories, (3) the density of endangered species per area, and (4) temporal changes in endangered species density. Habitats were classified into nine categories based on the flora and botanical books: grasslands, wetlands, coastal areas, rocky areas, farmlands, roadsides, forests, forest edges, and aquatic environments. The total number of endangered species was highest in forests, followed by wetlands, rocky areas, grasslands, forest edges, and coastal areas. In contrast, endangered species density per area was highest in rocky areas, followed by coastal areas, wetlands, grasslands, roadsides, forest environments, and farmlands. From the late 1970s to 2021, the increase rate of endangered species density was highest in rocky areas, approximately 2.7 times that of forests, followed by grasslands and coastal areas. These results suggest that, considering the density of endangered species per unit area and the rate of habitat area decline, it is highly likely that an “extinction debt” is accumulating in non-forest habitats, suggesting a particularly urgent need for conservation. Grasslands and wetlands face threats such as natural succession leading to forestation, coastal areas face threats from construction and development, and rocky habitats (especially in alpine regions) face threats such as climate change. Future land use policies must strive to avoid the loss of these habitats as much as possible.