Japan’s Declining Population Linked to Biodiversity Loss, Study Finds
A new study published in July 2025 suggests that Japan’s shrinking population, particularly in agricultural regions, is contributing to a concerning decline in biodiversity, a trend researchers warn could spread across East Asia and beyond.
The research, conducted by teams from the University of Sheffield, Tokyo City University, and Kindai University, challenges the assumption that fewer people automatically equate to ecological recovery. Instead, it reveals a complex interplay between demographic shifts, land use changes, and the enduring impact of human activity on natural ecosystems.
“Japan’s biodiversity has long been sustained by traditional rural livelihood practices such as wet rice agriculture, forest and soil management, and the maintenance of rural landscapes,” explained Kei Uchida, Associate Professor at Tokyo City University. “These human activities have shaped and supported ecological richness for centuries.”
However, the study highlights a troubling paradox. As populations dwindle, rural areas are experiencing an uneven pattern of change. Some areas continue to see human intervention, while others are abandoned to “ecological succession,” leading to a fragmented landscape that is, in fact, accelerating environmental degradation. “This uneven pattern of change produces a mosaic landscape which is accelerating the degradation of rural environments and undermining the biodiversity they support,” Uchida added.
The findings, appearing in the journal Nature Sustainability, add to a growing body of evidence demonstrating that simply removing humans from an area doesn’t guarantee “rewilding” – the restoration of ecosystems. The research underscores the need for proactive and nuanced conservation strategies.
Researchers have designated Japan as a “Depopulation Vanguard Country” (DVC) for East Asia, meaning it’s experiencing demographic trends that are likely to be mirrored throughout the region as global fertility rates continue to fall. “Japan is one of many countries whose demographic trends point to long-term population loss,” stated Peter Matanle, Senior Lecturer in Japanese Studies at the University of Sheffield. “We find that expected biodiversity gains from fewer people may not be occurring, and that losses are continuing. This indicates possible similar effects in other world regions such as Southern Europe, with Italy as its DVC, and Eastern Europe, with Bulgaria and Latvia as its DVCs.”
Analyzing the Data
The study’s conclusions are based on a comprehensive analysis of population data, land use patterns, and surface temperature across rural Japan. Researchers compared this information to changes in biodiversity among 464 species of birds, butterflies, fireflies, and frog spawn, as well as 2,922 native and non-native plant species, over a period of five to 17 years starting in 2004.
Notably, the research leveraged data collected by a large network of citizen scientists across Japan, resulting in a dataset of over 1.5 million observations – making it one of the most extensive studies of its kind.
The analysis revealed that biodiversity losses were observed in the majority of species studied, regardless of whether the human population in a given area was increasing or decreasing. Researchers attribute this primarily to shifts in agricultural land use, including urbanization, abandonment of farmland, and the intensification of existing agricultural practices. Only in areas where human populations remained stable did biodiversity appear to remain relatively stable as well.
Implications for a Depopulating World
With the United Nations projecting that 85 countries will experience continuous population decline by 2050, the study’s findings have far-reaching implications. Researchers believe the insights gained from Japan’s experience could be valuable for nations outside of East Asia, particularly those in Southern and Eastern Europe where below-replacement fertility rates and outward migration are prevalent.
The study calls for more effective government policies that strike a balance between promoting rewilding initiatives and supporting sustainable economic growth in rural areas. Addressing the complex relationship between population dynamics and biodiversity will be crucial for safeguarding ecosystems in a rapidly changing world.
Source: Tokyo City University; Image: Shutterstock
The study can be found at Biodiversity change under human depopulation in Japan
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