Several hundred green activists, some donning masks made from tree bark, staged a protest on Sunday in the Polish capital, Warsaw, against the felling of thousands of diseased trees in one of Europe's oldest woodlands, the Bialowieza Forest. The government has said that up to 400,000 trees will have to go because they have been infested by spruce bark beetles. But critics of the plan insist the forest can regenerate itself by its own natural powers. Often described as the "last untouched wilderness of Europe", Bialowieza National Park, part of the forest, is the only one of its kind out of Poland's 23 national parks. Its inner zone belongs to the realm of old-growth forest which has been living without much human intervention for almost 800 years. Only scientists are allowed free navigation through the strictly protected area.