In the second half of the 20th century the character of the Jizera Mountains changed completely. The German population of the area was expelled in 1945 and replaced by Poles on the now Polish and Czechs on the Czechoslovakian side of the mountains. The ecosystem was badly hit by emissions, produced by lignite fired power stations located in the Zittau basin, part of Europe's ecological Black Triangle. Weakened spruce forest, less resistant against various types of parasites, were on the verge of extinction. The higher parts of the mountains, once densely wooded, became largely treeless, in part also because of excessive deforestation. New roads cut through the once-secluded landscape.