Judging by the pages of recent journals and books, one could easily believe biodiversity conservation is experiencing a crisis. New phrases and metaphors abound, making for great headlines. Protecting the Wild is one of two new volumes that are entirely motivated by this supposed fracture in conservation. From a quick look at these books, one would think that there are thousands of scientists and conservationists in the streets, calling for the end of protected areas. Of course, this is far from reality. Even the volume's archenemy, Peter Kareiva, is not explicitly opposed to parks; rather, his focus just happens to be on all the stuff outside of parks and wilderness: “Conservation will likely continue to create parks and wilderness areas, but that will be just one of the field's larger goals. The bigger questions… regard what will we do with the rest of it.” Arguments for silver bullets, however, make better copy than cost–benefit analyses do.
Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.