The wood-pasture hypothesis (also known as the Vera hypothesis and the megaherbivore theory) is a scientific hypothesis positing that open and semi-open pastures and wood-pastures formed the predominant type of landscape in post-glacial temperate Europe, rather than the common belief of primeval forests. The hypothesis proposes that such a landscape would be formed and maintained by large wild herbivores. Although others, including landscape ecologist Oliver Rackham, had previously expressed similar ideas, it was the Dutch researcher Frans Vera, who, in his 2000 book Grazing Ecology and Forest History, first developed a comprehensive framework for such ideas and formulated them into a theorem. Vera's proposals, although highly controversial, came at a time when the role grazers played in woodlands was increasingly being reconsidered, and are credited for ushering in a period of increased reassessment and interdisciplinary research in European conservation theory and practice. Although Vera largely focused his research on the European situation, his findings could also be applied to other temperate ecological regions worldwide, especially the broadleaved ones.
Vera's ideas have met with both rejection and approval in the scientific community, and continue to lay an important foundation for the rewilding-movement. While his proposals for widespread semi-open savanna as the predominant landscape of temperate Europe in the early to mid-Holocene have at large been rejected, they do partially agree with the established wisdom about vegetation structure during previous interglacials. Moreover, modern research has shown that, under the current climate, free-roaming large grazers can indeed influence and even temporarily halt vegetation succession. Whether the Holocene prior to the rise of agriculture provides an adequate approximation to a state of "pristine nature" at all has also been questioned, since by that time anatomically modern humans had already been omnipresent in Europe for millennia, with in all likelihood profound effects on the environment.
The severe loss of megafauna at the end of the Pleistocene and beginning of the Holocene known as the Quaternary extinction event, which is frequently linked to human activities, did not leave Europe unscathed and brought about a profound change in the European large mammal assemblage and thus ecosystems as a whole, which probably also affected vegetation patterns. The assumption, however, that the pre-Neolithic represents pristine conditions is a prerequisite for both the "high-forest theory" and the Vera hypothesis in their respective original forms. Whether or not the hypothesis is supported may thus further depend on whether or not the pre-Neolithic Holocene is accepted as a baseline for pristine nature, and thus also on whether the Quaternary extinction of megafauna is considered (primarily) natural or man-made.
Vera's hypothesis has important repercussions for nature conservation especially, because it advocates for a reorientation of emphasis away from the protection of old-growth forest (as per the competing high forest theory) and towards the conservation of open and semi-open grasslands and wood pastures, through extensive grazing. This aspect in particular has attracted considerable attention, and has made Vera's hypothesis an important point of reference for conservation grazing and rewilding initiatives. The wood-pasture hypothesis also has points of contact with traditional agricultural practices in Europe, which may conserve biodiversity in a similar way to wild herbivore herds.