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STORY: This fence cutting through Poland's Bialowieza forest, on the country's border with Belarus, is meant to stop the flow of migrants.

But it is also hampering the movement of the Bialowieza lynxes and could lead to their extinction, researchers says.

Before the border wall’s completion in late June, about 40 of the lynxes, which are protected by Polish law, inhabited the dense forest.

It is a UNESCO World Heritage site and an EU Natura 2000 special area of conservation.

It is unclear how many of the lynxes stayed on the Polish side after the barrier was built.

But the population is likely to be divided between the two sides, says the Mammal Research Institute at the Polish Academy of Sciences.

Rafal Kowalczyk is a scientist there:

"Lynxes used areas on both sides of the border, they had areas on both sides of the border and functioned as one population. Now, dividing the forest into two separate ecosystems will cause the population of these animals to be separated. In the case of lynx, it is so important that we already know that this population was partially isolated, it was characterized by a very low genetic variation, the lowest among European populations."

Kowalczyk says his research showed that lynxes used to cross through the fence in Belarus undisturbed about 50 to 60 times a year.

Poland's border guard says the fence does not constitute an obstacle for animals as it has 24 gates for large creatures to go through if needed, which will enable continuous migration.