Complex sentence: Of this area, 57.9% is used for agricultural purposes, 30% is forested, 7.9% is settled (buildings or roads) and the remainder (4.2%) is non-productive (rivers, glaciers or mountains).
Split into simpler sentences: Of this area, 57.9% is used for agricultural purposes, while 30% is forested. Of the rest of the land, 7.9% is settled (buildings or roads) and the remainder (4.2%) is non-productive (rivers, glaciers or mountains).