Centuries ago the farmers of Extremadura (the region of Spain where Monfragüe is situated) discovered that the forests of evergreen oak that covered the land could provide essential shade and sustenance for their flocks.a So instead of felling all the trees to provide grazing land, they conserved sufficient oaks to create an open woodland. They also pruned the trees to encourage their branches to spread out. The shade of these venerable oak trees protected the grassy pastures beneath, and their bounteous harvest of acorns provided nutritious food for cattle and pigs. Since this dehesa preserved a significant part of the original tree cover, many native species of birds and animals could survive.