A Fence Through the Herd

The Białowieża Forest is one wood with two national park administrations, and since 2022 there has been a steel wall down the middle of it. On the Belarusian side the trees run to a cleared strip and the strip runs to a line of posts five and a half metres high, topped with wire, with no gap a large animal can use. Roughly three fifths of the forest lies in Belarus and is administered from Kamyanyuki as Belovezhskaya Pushcha; the rest is in Poland, which built the wall.

What that divides is not scenery. It is the largest surviving fragment of the lowland forest that once ran across the north European plain, and the population of European bison that was put back into it after the species had been extinct in the wild for a quarter of a century. Every one of those animals descends from twelve individuals. Their recovery is the most complete large-mammal restoration Europe has managed; it took ninety years and the cooperation of two states, and the open question now is how much of it a fence takes back.

Twelve animals

Bison bonasus was hunted out in two stages. The last free-living animals in Białowieża were killed around the end of the First World War — 1919 is the usual date and the precise one is disputed — after four years of occupation in which the forest was felled for timber and the herd was eaten. The last wild individuals anywhere were shot in the western Caucasus in 1927. What remained was fifty-four animals scattered across European zoos and private parks, of which only twelve turned out to have living descendants. The European Bison Pedigree Book has recorded every birth since 1932 — kept in Germany at first, and at Białowieża since 1947 — which is why those founders can still be named. Animals were brought back to the forest in 1929, held in enclosures for two decades, and the first were released to live free in 1952. In December 2020 the IUCN moved the species from Vulnerable to Near Threatened — an unremarkable-sounding administrative step, and for a mammal that was extinct in the wild inside living memory, close to unheard of.

One forest, two states

The line through the trees was drawn in 1945 and for most of its life it was quiet. UNESCO inscribed the Polish side in 1979, extended the property across the border to take in the Belarusian part in 1992, and enlarged it again in 2014, so on paper this is a single transboundary World Heritage property with a joint management framework and joint monitoring. On 8 December 1991, in a state hunting lodge at Viskuli inside the Belarusian part, the leaders of Russia, Ukraine and Belarus signed the agreement that dissolved the Soviet Union; the border in the forest stopped being the edge of a bloc and became the edge of a country. The two park administrations went on counting bison separately and reading the counts together, which is the only way a shared population can sensibly be managed.

Restoring the bison took ninety years and the cooperation of two states. Dividing them again took six months and required the cooperation of neither.

Why the wall went up

From the summer of 2021, people from Iraq, Syria, Afghanistan and a dozen other countries flew into Minsk on newly available routes and were moved to the European Union frontier. The EU called it state-organised instrumentalisation of migrants; Belarus denied organising anything. Poland declared a state of emergency along the border on 2 September 2021 and closed a three-kilometre strip to journalists, aid workers and anyone who did not live in it — the strip took in the forest. People died in the woods and marshes on both sides through that winter and afterwards; the recorded number runs to dozens and nobody, on any side, claims the record is complete. Poland began the permanent barrier in January 2022 and had 186 kilometres of it standing by June, at a reported cost of around 1.6 billion złoty. The section through Białowieża was the part fought over hardest, and the Polish Academy of Sciences' Mammal Research Institute, which sits in the village of Białowieża and has worked in this forest since the 1950s, was among the loudest objectors.

What a fence does to a population

The barrier has openings at intervals, sized for animals a great deal smaller than a bison. Bison cannot pass it. Neither can elk, red deer, lynx or wolf. The immediate consequence is not mortality but division: two populations where there was one, each smaller than the total, each breeding only within itself. Small closed populations lose genetic variation, and this species starts from an unusually poor hand — everything alive traces to twelve founders, and inbreeding depression in the herd is a documented problem rather than a theoretical worry. Researchers on both sides had spent decades treating the forest's bison as one management unit, with animals crossing and the numbers read as a whole. Since 2022 the two administrations publish figures that describe two different things. The Belarusian herd runs to several hundred and the park counts it every year; the forest total is well over a thousand, the largest concentration anywhere, and it has quietly become a sum rather than a population.

The view from Kamyanyuki

Belovezhskaya Pushcha on the Belarusian side is roughly 150,000 hectares of national park with its own research staff, its own enclosures, a hotel, and a network of forest roads laid out to be cycled. Its position is that it did not build the wall and was not consulted about it, which is true, and that the animals belong to a forest rather than to a state, which is the argument conservation has always made about borders and has never once won. Poland's position is that a state may fence its own frontier, which is also true. Both are governments talking past each other about a herd that reads neither statement.

The mechanisms that exist are slow ones. IUCN and the World Heritage Committee have raised the barrier as a concern for a property whose listing assumes cross-border management, and that is the lever — reports, missions, recommendations, delivered at the speed of committees. Nothing about the current relationship between Minsk and Warsaw suggests the joint monitoring restarts soon; the frontier zone on the Belarusian side needs a permit, the equivalent Polish strip has spent years under access restrictions, and field scientists who used to compare data across the line largely no longer do. Meanwhile the interesting number is not the wall's length but its lifespan. Fences are cheap to build and cheap to leave standing, and the political conditions that produced this one are not going to be resolved on a conservation timescale. A bison cow has a calf a year at best. The arithmetic of a closed population is patient, it is not reversible by apology, and it started running in June 2022.