This ecological balance was permanently destroyed, however, by the colonization and clearing of woodland that took place during the Middle Ages. Clearance by burning, the use of land for the production of straw and the unrestricted exploitation of the forest for raw materials and fuel led, little by little, to the devastation of wide areas of woodland, something that reached its peak in the 17th and 18th centuries (see Settlement history). This situation made the introduction of properly regulated forest management pressingly urgent - management that not only put a priority on controlled exploitation, but above all on care and sustainability. So in the 18th and 19th centuries, cleared land was reforested, mainly with undemanding, rapid-growing pines, which were followed in the 19th century by other non-native coniferous species such as spruce, larch, Weymouth pine and Douglas fir. In the Palatine Forest, this regulated management produced mixed woodland, in which coniferous trees formed around two-thirds of the total stock in areas that had historically comprised mainly oak and beech. Not until recent decades were there increasing attempts to turn larger areas of the forest into near-natural mixed woodland with a better ratio of deciduous to coniferous trees of around 50% (see adjacent table).