Population loss in Japan's countryside linked to declining biodiversity

Biodiversity is declining across Japan’s countryside, even as villages empty and young people move to the cities. Many would expect birds, insects, and native plants to return when humans leave. A new study shows that’s not happening.

The research team examined land-use change, temperature records, and nearly two decades of citizen-science observations.

Population loss doesn’t equal biodiversity gain

The researchers mapped population change across rural Japan and overlaid 1.5 million sightings of 464 animal species and 2,922 plant species collected between 2004 and 2021.

Shrinking towns did not rebound ecologically. Instead, abandoned rice fields turned into either housing estates or weed-choked lots. Both outcomes hurt wildlife.

Study co-author Dr Peter Matanle is a senior lecturer in Japanese Ssudies at the University of Sheffield.

“Japan is one of many countries whose demographic trends point to long-term population loss. We call it a ‘Depopulation Vanguard Country’ because it presages losses in similar neighboring countries such as South Korea and China,” said Dr. Matanle.

“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.

Dr. Matanle noted that his team would like to study other regions in the future such as Europe and Latin America to find out if similar effects are being felt there.

Citizen scientists fill the data gap

Volunteers across Japan recorded birds, butterflies, fireflies, frog spawn, and local flora. Their notebooks and apps supplied one of the richest ecological datasets on Earth.

The study shows how community monitoring can spot silent declines that official surveys might miss.

The study suggests that modest, steady farming often supports more life than sudden abandonment. When fields are left untended, invasive weeds can outcompete native plants. Without people to manage canals and paddies, wetlands dry out and the species they harbor disappear.

Traditional practices support biodiversity

“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. These human activities have shaped and supported ecological richness for centuries,” said Kei Uchida, an associate professor at Tokyo City University.

“Even as populations decline, human interventions continue in some areas, while others are left to ecological succession. This uneven pattern of change produces a mosaic landscape which is accelerating the degradation of rural environments and undermining the biodiversity they support.”

According to Professor Uchida, the research has implications for maintaining biodiversity in other depopulating countries in East Asia, and contributes to knowledge about the outcomes of human depopulation worldwide.

Population loss is a global issue

The United Nations expects 85 countries to decline in population by 2050, including much of Eastern and Southern Europe. The researchers urge governments to blend rewilding with rural job programs so that landscapes do not slide into neglect.

Shorter workweeks for farmers, subsidies for low-impact cultivation, and support for local wildlife groups are among the proposed ideas.

The lesson is clear: people leaving an area can harm nature as easily as they can help it. Careful planning is needed to tip the balance toward recovery.

Population and biodiversity loss

Biodiversity loss is not just a local issue – it’s a global concern that affects ecosystems, economies, and everyday life. The decline of species, whether plants, insects, or animals, disrupts food chains, weakens soil health, and reduces the resilience of natural systems.

When biodiversity shrinks, the services ecosystems provide – like pollination, water purification, and climate regulation – begin to break down.

In Japan, the study highlights how biodiversity continues to decline even as people leave rural areas. But similar trends are being seen worldwide, in both developed and developing regions.

Land-use change, habitat fragmentation, invasive species, pollution, and climate change all contribute to the problem. Even regions experiencing depopulation are not immune – sometimes, they’re more vulnerable if the land is mismanaged or neglected.

New strategies to protect wildlife

This research adds to the growing body of evidence that simply removing human pressure isn’t always enough.

Without intentional support, many landscapes fail to recover. Rewilding, conservation, and traditional ecological practices all have a role to play in reversing the loss.

As countries face changing demographics and population loss, preserving biodiversity will require new strategies that account for both ecological and social realities.

The full study was published in the journal Nature Sustainability.

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