Rural depopulation can harm biodiversity as well as urban expansion, according to research from Japan and other regions. Many species depend on the grasslands, rice fields, forest edges and other habitats maintained by people through low-intensity farming and regular disturbance. As populations leave the countryside, those activities stop, landscapes become overgrown or fragmented, and species that once benefited from human stewardship can disappear.
Less than an hour by train from central Tokyo, ecologist Kei Uchida walks through groves of wild cherry trees and grasslands filled with elephant-tall pampas grass. On the roadside, he spots a ball of knee-high grass stalks woven together. It is a small Eurasian Mus musculus (micromysminutus), a species in decline in the region and a target for conservation.
Ecosystems depend on humans. Don’t abandon humans.
Volunteers saved this area around Mount Tenran from development 30 years ago. They now monitor its plants and animals, thin the forest, and plant and harvest rice, all in the name of biodiversity. In the shallow waters of the rice fields, tiny fish swim among the stems, while dragonflies mate above the surface. At dusk, fireflies rise over the fields.
Uchida, an environmental scientist at Tokyo City University in Yokohama, and his colleagues included the site in a study of thousands of species across more than 150 forests, farmlands and “peri-urban” landscapes in Japan.1 The results were not surprising in one respect: where human populations are growing, the diversity and abundance of most species are declining. But the researchers also found that biodiversity is declining in areas where the number of people is falling.
That finding, echoed by research from other parts of the world, challenges the common assumption that nature always flourishes when people leave.
Japan and many other countries are seeing rural areas emptied as people move to urban centres. Research shows that this can damage biodiversity in depopulated areas and create new conservation challenges.2 Conservationists therefore need to look beyond establishing and managing protected areas. In some ecosystems, they may also need to recruit, train and support people who can live there and maintain the habitats.
Maintaining the satoyama landscape
I joined Uchida and local volunteers to learn how human activity can increase biodiversity. Uchida says the area is typical of the satoyama landscape, a term combining the Japanese words for village and mountain. “Agriculture and living things can coexist,” he says.
Japan’s satoyama landscapes are being lost as populations decline and urbanisation advances. Around Mount Tenran, as in many forested parts of Japan, people cut trees for fuel and removed fallen leaves for fertiliser for centuries. Those activities kept the forest open and benefited particular plants and insects. When they stopped, the forest became denser and more shaded.
“We’ve been using forests for 1,000 years, but we haven’t been using them recently,” Uchida says. Young students are now given small handsaws and taught traditional techniques for thinning the forest.
Tsubasa Kojima, a volunteer who observes nature in the area, showed us where fireflies are counted at night. Two types live there. Small Heike fireflies (outer aquatica) prefer rice fields, whereas the larger, brighter Genji fireflies (Nipponorciola crucciata) are associated with running water.
“You rarely see both at the same time,” Kojima says proudly. He counted 60 fireflies in the rice field four days earlier. Often, he is joined by urban residents who come to admire the countryside at dusk. After the display, however, most board a train and return to brightly lit Tokyo.
The consequences of rural decline
Many people in Japan now have to travel to see fireflies, although the insects were once common outside homes. The pattern is widespread. In 1950, almost 40% of the world’s population lived in rural areas. According to United Nations data, only 19% of the world’s 8.2 billion people currently live in rural areas. The global rural population is expected to peak in the 2040s and then decline.
Japan is already far along that path. Its total population fell by 4 million people between 2015 and 2025, while the rural population declined even more rapidly. In 2025, only 8.6% of the population was classified as rural.
Peter Matanle, an independent environmental and social scientist who worked with Uchida on the biodiversity research, describes Japan as an “avant-garde country” from which other nations can learn about population decline. European Union data show that rural Europe lost 0.2% of its population per year between 2015 and 2024. Rural areas also tend to have older populations than cities, suggesting that further decline may follow.
Uchida and his co-authors examined data on 464 species of birds, butterflies, fireflies and frogs, as well as about 3,000 plant species. The data came from different Japanese landscapes and covered periods of between five and 17 years beginning in 2004.
Biodiversity declined where landscape destruction was greater. That destruction could result from people moving into an area and building infrastructure, or from agricultural intensification, in which small family farms are replaced by corporate operations.
Rewilding the Earth: How seven artificial islands can help a dying Dutch lake
The researchers also recorded biodiversity declines in areas abandoned by people. Although this may seem paradoxical, amphibians and many insects cannot reproduce when irrigation stops. Other ecological niches disappear as well. Dry, abandoned landscapes can become too fragmented for many species to recolonise.
“It’s not going to be good for anyone if we let it go,” Matanle says.
A similar relationship between rural population decline and biodiversity has been documented in Europe. A study of 70 sites in Albania, Bulgaria, Croatia and Greece found that rural abandonment “consistently has negative impacts on bird communities”.2 The species most affected were those living in agricultural areas.
A European Commission monitoring system found that European agricultural bird populations declined by 58% between 1980 and 2024. Agriculture intensified in some places and disappeared from others.
Birds are not the only animals to have benefited from human-managed environments. In Sweden, semi-natural grasslands cleared by people and kept open by livestock are the main habitat for one-third of the country’s endangered species. They can support up to 40 plant species per square metre.3
After the Second World War, the total area of grassland fell by more than 90% in some regions as people left the countryside and land use changed.4 In many cases, the loss of grazing animals allowed land to become row crops or forest, either through natural tree growth or deliberate timber planting. Both types of forest support less biodiversity than the semi-natural grasslands they replaced.
In Spain, Francisco Lloret, an ecologist at the Autonomous University of Barcelona, says biodiversity falls when people leave the countryside because some species lose habitat while others lose food. Vultures and other scavengers, for example, have depended on livestock for centuries, but that food source is disappearing.
Revolution is sweeping Europe’s farms: Can revolution save agriculture?
Wooded and herbaceous areas at the edges of fields are also disappearing. In Mediterranean countries such as Spain, fields are often bordered by grasses or dry-stone walls that shelter many vertebrates and invertebrates. When the walls are removed to create larger fields for modern farming systems that require fewer workers, those organisms are lost.
Why moderate disturbance can help
The reasons species thrive in low-intensity agricultural landscapes vary. Some organisms need the standing water of rice fields. Others depend on grasslands kept open by mowing or livestock, or on the edges between forests and open land.
The broader pattern, however, is that many species depend on mosaic habitats maintained by regular, moderate disturbance. Seasonal flooding, grazing, burning, forest thinning and patchy logging can create a mixture of conditions. Landscapes inhabited and managed by people can therefore contain more species than large areas of undisturbed forest.
These are the Arcadian landscapes depicted by Romantic poets, in The Wind in the Willows (1908) and in My Neighbour Totoro: culturally beloved ecosystems that have supported a wide range of species since at least the Iron Age.
“Biodiversity has evolved together with people and human activities over the past millennia,” Lloret says. Some species may even have evolved to be better suited to human-managed landscapes. But he cautions that there are no universal rules: context is crucial.
In some places, biodiversity may increase as populations decline. Large predators such as wolves often do best in areas with few people. In the tropics, the most biodiverse regions on Earth, relatively few countries are experiencing population declines, so habitat loss remains the more pressing concern.
How does nature need humans?
In response to biodiversity loss associated with rural depopulation, conservation researchers from the Czech Republic and Poland have proposed small-scale farming as a tool for protecting farmland birds.5 They argue that such rural areas would also have “high aesthetic and heritage value”.
Uchida and his colleagues propose a “new interventionist rewilding” to complement rewilding projects that aim to let nature function with minimal human involvement. Some European Union schemes support farmers and biodiversity, although they have been criticised as ineffective.6
As the volunteers and Uchida finished their hike and emerged from the forest, the sky opened and rain began to fall. We went to a nearby bakery for curry bread, a popular Japanese snack, and returned to a question that had occupied me throughout the day: who will create habitat for endangered species in the countryside in the future?
Source: www.nature.com
