Depopulation and Biodiversity: Will Fewer People Save Nature?
- Natasha Dudek
- Jul 11, 2025
- 5 min read
We are in the middle of a biodiversity crisis. Since 1970, the world has lost 73% of its wildlife populations. Scientists warn that Earth’s sixth mass extinction may be underway, with species disappearing 100 to 1,000 times faster than before humans began altering the planet.
It’s clear that as the human population grows, biodiversity tends to decline. But what happens when the population shrinks? Could a shrinking human footprint slow, or even reverse, biodiversity loss? Could we see a “depopulation dividend” for nature?
A new study published in Nature Sustainability (June 2025) by researchers from Tokyo City University, The University of Tokyo, the University of Sheffield, Kindai University, and the Nature Conservation Society of Japan takes a hard look at this question. Their findings challenge some hopeful assumptions and offer essential insights for the future of conservation.
Japan: A Global Test Case
Japan is uniquely positioned to explore the relationship between depopulation and biodiversity. Its national population has been shrinking since 2010, with 23 of 47 prefectures already declining since 1995. In many rural areas, the population has been falling steadily for decades.
Japan is also one of the world’s biodiversity hotspots, home to rich and threatened ecosystems. Unlike other hotspots where human population growth threatens habitats, Japan presents a rare case of biodiversity under depopulation.
Researchers studied 158 sites across Japan’s wooded, agricultural, and peri-urban ecosystems landscapes, monitoring 464 species of birds, butterflies, fireflies, frogs, and 2,922 native and non-native plant species from 2004 to 2021.
What They Found: Despite Depopulation, Biodiversity Is Still Declining
The researchers set out to answer a key question: is biodiversity improving in places where human populations are shrinking? Their findings suggest the opposite. Biodiversity losses continued across most of the 158 sites studied, regardless of whether local populations were increasing or declining. In areas experiencing depopulation, both the abundance and species richness of most organisms, especially frogs and fireflies, fell sharply. The only group to consistently increase was non-native plant species, which likely signals ecological imbalance.
The decline in biodiversity isn’t driven by population loss alone, but by what comes next: major shifts in land use. Even as communities shrink, urban development continues to expand. Vacated land (residential or agricultural) is often left unmanaged or sold to developers, fueling sprawl and giving rise to new roads, shopping centers, sports facilities, housing developments, and parking lots. In other cases, farmland is consolidated into large-scale, industrial operations, such as intensive fruit and vegetable production under vast plastic hothouses.
Meanwhile, areas with relatively stable populations that continue traditional farming, like wet-rice cultivation, tend to show more stable biodiversity. But such regions are becoming rare, and many face looming ecological disruption as ageing accelerates.
Why Depopulation Isn’t Automatically Good for Nature
It’s tempting to think of depopulation as nature’s chance to reclaim space. But in Japan, the story is not one of quiet rewilding. Rather, it’s one of fragmentation and ecological drift. That’s because depopulation unfolds gradually, not dramatically. Houses sit empty, fields are left fallow, and infrastructure like roads, utility lines, and concrete channels linger, decaying slowly but rarely removed.
Rather than reverting to wild, biodiverse ecosystems, abandoned land is often funneled into two directions: sprawling urban development or industrial-scale monoculture. Former rice fields may be paved over for roads, shopping complexes, or suburban neighborhoods. Others are absorbed into consolidated farms that prioritize productivity over biodiversity, like mass-producing crops under vast plastic greenhouses.
This isn’t the natural world bouncing back; it’s a slow-motion ecological unraveling. The loss of traditional practices, like seasonal rice farming, forest thinning, and water management, means the disappearance of habitats that depended on them. Japan’s semi-natural traditional farming ecosystems were never truly “wild,” but they were rich in biodiversity thanks to human stewardship. As these practices vanish, so too does the delicate ecological balance they maintained.
Without active restoration or reimagined stewardship, depopulation does not automatically benefit biodiversity. Instead, it results in degraded landscapes, neither fully human nor truly natural, that are far less hospitable to the species that once thrived there and become prime targets for developers seeking to create urban infrastructure.
The Global Implications
Japan isn’t alone in experiencing depopulation. According to the UN, by 2050, 85 countries will be experiencing sustained population decline, including many in Northeast Asia and Eastern Europe. Without a clear understanding of how depopulation impacts ecosystems, we risk missing a crucial opportunity, or worse, continuing biodiversity losses under the illusion of progress.
While every region will have its own unique context, the findings suggest that passively waiting for nature to recover as people leave is unlikely to succeed. Instead, the future of conservation in depopulating areas depends on active habitat management, targeted rewilding efforts, and long-term ecological planning.
The Way Forward: Planning, Not Hoping
Depopulation won’t automatically lead to a biodiversity revival, but it can create new opportunities for regenerative, socially and ecologically meaningful change. The key is not to wait and hope, but to actively plan.
Around the world, rewilding is gaining momentum as a strategy to restore ecosystems and rebuild resilience. But in places like Japan, where landscapes have been shaped for centuries by practices like wet-rice agriculture, rewilding won’t mean returning to a pre-human past. A powerful example of this is the Knepp Castle Estate in the UK. Once intensively farmed, Knepp was transformed starting in 2001 into one of Europe’s most influential rewilding projects. Knepp’s rewilding process relied on natural processes, such as reintroducing free-roaming grazing animals to mimic ancient herbivore activity, to drive habitat regeneration and restore ecological complexity. The result has been astonishing: species once vanishing from the British countryside, like turtle doves and nightingales, are now breeding again, and more common species are thriving.
Knepp also demonstrates how ecological restoration can support vibrant, resilient rural economies. Its rewilding supports nature-based enterprises such as high-quality meat production, camping, glamping, wildlife safaris, and business rentals, revitalizing the local economy and boosting business for nearby pubs, shops, and B&Bs. The success of Knepp shows that even low-cost restoration of abandoned farmland can deliver dramatic biodiversity gains while creating new economic opportunities. Ultimately, rewilding at Knepp wasn’t about removing people, but about reimagining their role.
Nature won't bounce back on its own. But with intentional, well-informed strategies, we can guide the transition to a lower population toward something ecologically richer, more resilient, and better aligned with the changing human landscape.