The subalpine belt of the Pyrenees, once forested, is now a mosaic of forest patches and open landscapes with pastures. We reconstruct the palaeoenvironmental history using sedimentary ancient DNA, pollen and charcoal. We show that Neoglacial cooling initially opened the forest, and pastoralism through fire and grazing maintained it. These landscapes result not from climate or humans alone, but from their long-term synergy, implying that conservation must emulate traditional herding practices.