The oak tree was a boon companion as humans expanded their presence across much of the globe. While oak woodlands (Quercus spp.) come today in stunningly diverse forms, the stately dehesas of Spain and the dramatic oak-dominated ranchlands of California are working landscapes where cultivation and manipulation for a couple of millennia have shaped Mediterranean-type ecosystems into a profoundly modified yet productive environment that is sought-after by every manner ofspecies.

The grazing of wildlife and livestock in oak woodlands yields a remarkable plant and animal...