In the quiet valleys at the foot of Mount Tenran in Japan's Saitama Prefecture, volunteers with hand saws thin the forest, plant and harvest rice. The mountain is low, only 197 metres, and looks more like a large hill, but its surroundings are considered a typical satoyama, that is, a traditional landscape where villages sit alongside forest and fields. Volunteers at this site saved the area from development thirty years ago. Among the cherry groves and thickets of susuki grass nests the tiny harvest mouse, and in the rice paddies fireflies light up in the evenings. What we see before us is not wild nature in its pure form, but the result of constant yet gentle human intervention.
A study published in Nature Sustainability in 2025 called into question the familiar idea that the departure of people automatically restores nature. Scientists from the University of Sheffield and the Japanese universities of Tokyo City and Kindai studied forest, agricultural and suburban landscapes of Japan. They compared data on population, land use and temperature with more than 1,5 million observations of 464 species of birds, butterflies, fireflies and frog spawn, as well as of 2 922 plant species. They covered the period from 5 to 17 years, starting in 2004. The result was unexpected: biodiversity losses were recorded in most of the groups studied regardless of whether the region's population was growing or shrinking. Nature looked more stable only where the number of people did not change.
Researchers call Japan a "frontrunner country" of depopulation: in their view, what is already happening here may be repeated in South Korea and China in the coming decades. The country's population is shrinking rapidly. The 2025 census showed a decline of 2,5 % over five years, or 3,17 million people. The share of rural residents, according to the World Bank, is about 7,7 %. Emptying villages turn into two different scenarios, and both harm wildlife: some abandoned rice fields are built over, while others are overgrown with weeds. In Europe the picture is also not clear-cut. According to Eurostat, in 2015–2020 the population of predominantly rural regions of the EU declined by about 0,1 % a year, while another publication from the agency speaks of 0,2 % a year.
Semi-natural meadows, which people created over centuries through mowing and grazing, show especially well how this works. In Sweden about a third of red-listed species are associated with agricultural landscapes where such meadows have survived. In one square metre here one can often find about forty species of vascular plants, and sometimes more. However, over the past 100–150 years semi-natural habitats in the country have shrunk greatly, and most Swedish meadows today do not meet the criteria for good conservation status.
Many species have adapted to moderate and regular disturbance: to seasonal flooding of the paddies, grazing, forest thinning and the burning of grass. When these practices cease, the landscape gradually becomes overgrown with monotonous forest or dries out, and with it the habitats for amphibians, insects and grasses disappear. A good illustration is the Heike firefly: its populations have been declining rapidly in many areas of Japan in recent years, and in satoyama local communities restore water habitats specifically for it. The authors of the study emphasise that without targeted support such landscapes often do not recover, and it is not worth waiting for everything to sort itself out.
There is, however, a caveat to the conclusion. Where biodiversity took shape together with traditional land use, a simple "return of nature" can turn into a loss. It is precisely such places, by the logic of the study, that need the continuation of the customary care, not its cessation.
That is why the conversation about the future of the Japanese and European countryside comes down not to a choice between people and nature. The researchers call for combining renaturation with economic development and for relying on traditional practices. Support for small-scale farming and training local residents in caring for the land look here like a sensible alternative to nature reserves alone.
