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Poland violated EU law by ordering large-scale logging in one of Europe's oldest woodlands, the Bialowieza forest, the European Court of Justice has ruled.
Bialowieza forest has been designated a Unesco World Heritage site and is home to Europe's largest herd of nearly extinct bison.
But Poland argued its decision to order a three-fold increase in logging was necessary to combat beetle infestation.
Poland says it will respect the ruling.
The court's decision is a defeat for the country's conservative-led government.
The ECJ said Poland had "failed to fulfil its obligations" in directives covering the habitats of animals and birds.