French to Dutch Other Geology

I am translating an English text to Dutch which has been translated itself from French (original). It is a text about the geology of Peru.

The context of this term is: 'Les tentatives pour classifier les régions naturelles au Pérou sont nombreuses, en considérant les zones de vide, les éco-régions... (etc.)' In the English texts, 'zones de vide' has been translated as: 'empty areas', but 'lege gebieden' sounds a bit unprofessional to me. There must be a better term! Does anyone have any idea?