Settlement, logging and clearance has left forest pockets in the foothills with dense and continuous forest being found in the upper parts of the mountains. Due to logging in the last centuries little remains of the broad-leaf trees like beech, sycamore, ash and littleleaf linden that were once common in the Sudetes. Instead Norway spruce was planted in their place in the early 19th century, in some places amounting to monocultures. To provide more space for spruce plantations various peatlands were drained in the 19th and 20th century. Some spruce plantations have suffered severe damage as the seeds used came from lowland specimens that were not adapted to mountain conditions. Silver fir grow naturally in the Sudetes being more widespread in past times, before clearance since the Late Middle Ages and subsequent industrial pollution reduced the stands.