Overgrown agricultural machinery on a vacant farm near the Chernobyl Nuclear Power Plant in Ukraine.

Overgrown agricultural machinery on a vacant farm near the Chernobyl Nuclear Power Plant in Ukraine. Okla Michel / CTK via AP

Abandoned Lands: A Hidden Resource for Restoring Biodiversity

Abandoned farmland has been increasing, with a billion acres — an area half the size of Australia — lost globally. Ecologists are increasingly pointing to the potential of these lands and of degraded forests as neglected resources for rewilding and for capturing carbon.

Gergana Daskalova was nine months old when she was taken in by her grandparents in their small village in Bulgaria. It was soon after the fall of the Iron Curtain, and her parents had left for the city after the closure of the village’s state-run collective farm.

She grew up in a countryside emptying of people and with large areas of farmland lying abandoned. She eventually left too, traveling abroad and forging an academic career as an ecologist. But she never forgot her home village, where her childhood saw an ecological transformation paralleling the social one. As people left Tyurkmen, in Plovdiv province in southern Bulgaria, nature returned with a vengeance.

“Over the last three decades, I have seen Tyurkmen change as houses were abandoned, gardens engulfed by vegetation, and birds like pheasants and hoopoes became a more common sight than people,” she says. “The brambles are so thick, stepping on them feels like a trampoline. Looking back, it was these changes that inspired me to study ecology.”

But while most ecologists prefer to study pristine places, Daskalova has become one of a rising group of researchers focusing on the previously neglected ecology of abandoned land. She believes these neglected and often despised new wildernesses could be a crucial part of the planet’s salvation. If only we noticed and tended them, she says, they offer great opportunities for meeting both climate and biodiversity targets.

The scale of recent global farmland abandonment is a staggering and still largely untold story.

Abandonment, she says, is a “silent driver of biodiversity change. Yet there is still so much we don’t know about its imprint on the planet.” From her current research base at the International Institute for Applied Systems Analysis in Austria, Daskalova is working to change that, both globally and back home, where Bulgaria is a case study in the impact of population decline.

In the past 35 years, the country has seen the fastest decline in population of any country in the world — a 28 percent drop. Most of that exodus has been from the countryside, where for the past two years Daskalova has been researching 30 Bulgarian villages, including Tyurkmen, to chart in detail how nature is colonizing the abandoned land.

The scale of recent global farmland abandonment is a staggering and still largely untold story. We are used to seeing humans colonize nature. In the tropics that continues. But elsewhere the reverse is happening. Globally, an area of land half the size of Australia, around a billion acres, has recently been relinquished, Daskalova and Johannes Kamp of the University of Göttingen in Germany reported in Science in May.

This vast land bank is ripe for rewilding, they say, with huge potential to improve biodiversity and capture atmospheric carbon dioxide.

The stone remains of an abandoned house in Bulgaria.

The stone remains of an abandoned house in Bulgaria. Gergana Daskalova

Other researchers point out that so-called “degraded” forests — meaning forests that have been logged in the past but now often stand neither productive nor protected — represent a parallel bank of unused or underused land potentially vital to planetary salvation. A recent study found that globally, degraded forests cover an area almost the size of Russia. These forests are similarly underexplored by ecologists as reservoirs of biodiversity. And they are often ignored by policy makers for their potential in future ecological restoration and carbon capture.

In the cases of both abandoned farmland and degraded forests, researchers such as Daskalova say our preconceptions about categorizing land — as pristine forest, production forest, protected, farmland, or urban areas — too often blinds us to the environmental potential of these largely unmapped border lands, wastelands, backwoods, and no-go areas.

Abandoned farmland is growing fast. Despite increases in cultivated areas in many developing and tropical regions, the amount of land under agriculture globally has been in decline since 2001. Arable land in the United States has declined by almost a sixth in the past three decades. Europe has seen a similar retreat.

In parts of Africa, farming is seen as an old man’s activity, and fields lie neglected as the young head for jobs in the cities.

Some of the most extensive abandonment has been in the countries of the former Soviet Union. As state-run collective farms closed following the collapse of communism in 1991, few of these giant enterprises were subsequently cultivated by private farmers. In all, agriculture in the former Soviet Union has retreated from around 290 million acres, with some estimates putting the loss at as much as a third or more. Likewise, in a swath of Eastern Europe from Poland through Slovakia to Ukraine, an estimated 16 percent of farmland has been abandoned since 1988. In the Baltic state of Latvia, the figure is a staggering 42 percent.

Southern Europe is not so different. Greece, Italy, Spain, and Portugal never had collective farms, but the inexorable aging of their populations and the exodus of young people to cities is emptying villages and leaving fields and pastures untended. Francesco Cherubini of the Norwegian University of Science and Technology calculates that in the past three decades, Europe has seen a net loss of farmland larger than Switzerland.

The trend is surprisingly widespread. Japan, one of the most densely populated countries in the world, nonetheless has approaching 250,000 acres of farmland sitting idle. Even in parts of Africa, where populations continue to grow, farming is seen as an old man’s activity, and fields lie abandoned as the young head for jobs in the cities, notes Edward Mitchard, a researcher at the University of Edinburgh.

Königsbrücker Heath nature reserve in Saxony, Germany, is on a former Soviet Army training area.

Königsbrücker Heath nature reserve in Saxony, Germany, is on a former Soviet Army training area. Ullrich Gnoth / Alamy Stock Photo

Sometimes the abandonment is not driven by economic, demographic, or social factors, but by pollution or industrial disasters. Hundreds of square miles of radioactive former farmland around the stricken nuclear reactors at Chernobyl in Ukraine and Fukushima in Japan are now within exclusion zones and could be without human occupation for centuries to come.

Nature pays little regard to exclusion zones, however. Despite the radiation, wolves, bears, wild boar, lynx, and other large animals are reclaiming their former terrain, forests are encroaching, and carbon is being captured.

Other times, it is war that does the damage. In the past 19 months, swaths of eastern and southern Ukraine have been consumed by warfare following the Russian invasion. Despite the military mayhem, nature is in places taking over abandoned fields. And even when the war ends, minefields could leave the land unused and unproductive for decades.

While the retreat from farming, for whatever reason, is the largest source of abandoned land globally, there are other causes. For instance, the end of the Cold War has led to the abandonment of an estimated 5,800 square miles of former military training areas in Europe. Free of tanks and troops, many of these areas are becoming nature reserves, including the former British tank grounds at Lüneburg Heath in western Germany and the Königsbrücker Heath in eastern Germany vacated by Russian troops.

The collapse of collective farming in Russia has led to the sequestering annually of more than 40 million tons of carbon.

Left to its own devices, nature will usually reclaim abandoned places, with benefits for biodiversity and climate. Even without human intervention, carbon capture from the abandoned areas of Russia is already considerable. Irina Kurganova, a soil scientist with the Russian Academy of Sciences, estimates that the collapse of collective farming there has led to the sequestering annually of more than 40 million tons of carbon in natural vegetation and improved soils.

The unanswered questions are about what kind of nature returns and whether — by mapping, studying, managing, and protecting these vast tracts of abandoned land — we could increase their potential to meet global goals for climate change mitigation and the restoration of species and their habitats.

Not everyone is sanguine about the likely gains from natural regeneration on abandoned land, however. Some ecologists fear the growing invasion of unwelcome species.

A lone tree stands on a tsunami-scarred landscape near the devastated Fukushima Daiichi Nuclear Power Plant.

A lone tree stands on a tsunami-scarred landscape near the devastated Fukushima Daiichi Nuclear Power Plant. Christopher Furlong / Getty Images

In Poland, where 12 percent of agricultural land has been abandoned since 1990, as much as three-quarters of that land “is now dominated by invasive plant species such as golden rod, walnut and box elder maple,” according to Magdalena Landa of the country’s Institute of Nature Conservation. In the Bulgarian villages Daskalova has studied, she has found a profusion of ailanthus, a tree originally from China that she says is “relentless and nearly impossible to eradicate.”

Likewise, in a well-known example in the Southern U.S., an Asian vine called kudzu, which was first planted widely to restore lands deserted during the Dust Bowl era, has gone from being a boon to a curse, invading abandoned farmland, pastures, and woodland, wrecking buildings, downing power lines, and strangling trees.

Land abandonment has also been linked to soil erosion, desertification, and an increased risk of wildfires. The last in particular can undermine the potential of natural regeneration to capture carbon from the air. “Shrubbier landscapes can be susceptible to fires, tipping the balance from a carbon sink to a carbon source,” says Daskalova.

The reintroduction of wild grazing animals on areas of the Central Asia steppes no longer used for grazing could help limit fire risk.

This is a likely reason for a rapid growth in wildfires on the steppes of Russia and its neighbors in the past three decades. In a 2020 study, Kamp and Martin Freitag of the University of Munster found a threefold increase in wildfires across an estimated 770,000 square miles of northern Kazakhstan and southern Russia. It was concentrated in areas that had accumulated more grassy biomass since Soviet livestock stations were abandoned. The study quantified the process precisely. “When the grazing intensity fell below a threshold of four dung piles per 200 square metres [2150 square feet], fire frequency started to increase sharply,” it concluded.

So, what is to be done? In the Anthropocene, nature often needs help to meet our ecological expectations. The reintroduction of wild grazing animals — such as saiga antelope — could limit fire risk on the steppes of Central Asia, for instance. Elsewhere, control of invasive species may be needed. And, counterintuitively, keeping some people on the land helps too, says Daskalova.

She points out that landscapes containing lots of small farms, woodlands, and spare land — depopulated but not entirely abandoned — are typically richer in species than fully abandoned areas. This is because they have more ecological niches for often locally rare species, and invaders are less likely to take hold. Such areas are precious, she believes, because they provide “important opportunities for establishing protected areas managed by local people, where the focus is on protecting both biodiversity and human livelihoods.”

An abandoned farmhouse in Rijssen, Netherlands.

An abandoned farmhouse in Rijssen, Netherlands. Pierre Crom / Stringer via Getty Images

Similar strategies, combining local control and natural regeneration could also work to maximize the benefits from the world’s degraded forests. “There are over 1.5 billion hectares [3.7 billion acres, an area almost the size of Russia] of forests worldwide that retain 50-80 percent of their potential biomass,” says Tim Rayden at the Wildlife Conservation Society, in New York, who is author of a new study of their potential.

Often selectively logged in the past and then left behind, these are vital reservoirs of biodiversity, yet are frequently ignored in investigations into how forest and former forest lands could protect nature and soak up carbon dioxide. Rayden says restoring these areas to their full potential “could deliver rapid biodiversity and climate mitigation benefits” more quickly and cheaply, and with much less threat to existing land users, than planting on cleared land, which is often in use for farming.

“Forest restoration is sometimes presented as a trade-off between food security and nature,” says Rayden. But “there is so much scope … for nature restoration in degraded forests that don’t displace farming activity.”

An analysis found proper management of degraded forests in Mesoamerica could increase the carbon stored by two-thirds.

Rayden did an analysis of Mesoamerica that found that proper management of degraded forests could increase the amount of carbon stored in the region’s forests by two-thirds, compared to just targeting cleared former forest land.

Handing land back to nature is no silver bullet for either the world’s climate or biodiversity ills. But it does have huge potential if properly exploited and managed. Rayden believes active restoration of degraded forest could be the primary means of reforesting the planet and capturing carbon in land vegetation. Daskalova says that “land abandonment and human depopulation are a modern-day wildcard when it comes to their potential to conserve biodiversity and capture carbon.”

But both say we still have a blind spot for these in-between places — they are hiding in plain sight. Daskalova says her aim is to shine a light on them, “to find the optimal ways to use abandoned land for both nature and people.” Her upbringing in Bulgaria and studies of the backwoods of her depopulated homeland may deliver important lessons for us all.