The roar of a chainsaw and staccato blows of an axe break the silence deep in Poland's majestic Bialowieza forest as loggers swiftly fell a 90-year-old tree.

Teeming with wildlife, Bialowieza, a UNESCO World Heritage Site, includes one of the largest surviving parts of the primeval forest that covered the European plain ten thousand years ago.

But today, this peaceful haven is the scene of a bitter battle between environmentalists and officials over a spruce bark beetle infestation that rangers say is damaging healthy trees.

There is no denying spruce bark beetles are having a field day in the forest, also home to the continent's largest mammal, the European bison, as well as elk, wolves and lynx.

The wood of a logged spruce reveals a spectacular network of tunnels created by the insects.

"When their population gets as huge as it is now, the beetles are no longer content just to finish off diseased spruce. They also attack healthy trees," Andrzej Antczak, a local forest ranger told AFP.

Authorities insist the goal of the tree felling is to stop the degradation of the treasured woodland.

But environmentalists and many scientists argue the beetle poses no threat and that officials are more interested in selling wood than protecting the forest.

Spruce trees make up around 30 percent of Bialowieza and rangers say that beetles have attacked about a fifth of them, translating into about a million cubic metres (35 million cubic feet) of lumber.

Each infected tree threatens up to 30 of its neighbours. And warmer weather means that up to five generations of beetles can reproduce over a year.

Cutting a single infested tree and removing it, can "save one to two hectares (2.5-5 acres) of forest per year," Grzegorz Bielecki, head forest ranger at Bialowieza, told AFP.

Over the centuries, Bialowieza has been spared the loggers by Polish kings and Russian czars who treasured it as the perfect hunting ground brimming with large game.

The forest also survived massive clear-cut logging -- when all is felled down to the stem -- in the 20th-century by Russian and German occupiers, British industrialists and communist authorities.

Sprawling over 150,000 hectares (370,000 acres), Bialowieza reaches across the Polish border with Belarus, where it is entirely protected as a nature park, compared to only around 16 percent of the Polish part of the forest.

Green activists argue that the entire Polish part of the forest should be designated as a nature park, meaning logging would be forbidden.

But since it was elected in October 2015, the controversial Law and Justice (PiS) government has said it plans to harvest more than 180,000 cubic metres of wood over a decade -- triple the amount approved by the previous liberal government.

The PiS insist new trees outnumber ones that are being chopped down and that protected virgin woodlands will not be logged.

- 'Huge' infestation -

The governing conservatives claim logging will protect the forest from beetles and people from being hit by weakened, falling spruce.

Environmentalists, however, accuse rangers of altering the forest's unique ecosystem which is described by UNESCO as "an irreplaceable area for biodiversity conservation".

A coalition of environmental organisations, including Greenpeace and the Polish branch of the Worldwide Fund for Nature (WWF), has lodged a complaint with the European Commission over the logging.

The EU has also said it is "concerned" by Warsaw's decisions to log in Bialowieza and a UNESCO delegation is due to visit Poland from June 4 to 8.

Science professor Rafal Kowalczyk told AFP he opposes the felling, believing the beetle-ravaged trees should be allowed to die naturally and become a habitat for new flora and fauna.

"The trees around me look dead, but in reality they're brimming with life, even more so than when they were growing, because now they're home to hundreds of insect species," Kowalczyk said, standing in part of the forest where trees fell victim to beetles.

"A dead tree is a wealth of biodiversity," added the director of an outpost of the Polish Academy of Sciences in Bialowieza.

"To cut down trees in this forest is comparable to what the Taliban does when it destroys works of art!"

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HERITAGE OIL