Toward successful reintroductions: The combined importance of species traits, site quality, and restoration technique

Reintroduction of endangered plant species may be necessary to protect them from extinction, provide connectivity between populations, and reach recovery goals under the U.S. Endangered Species Act. But what factors affect reintroduction success? And which matter more: traits inherent to the species, qualities of the site, or reintroduction technique? Here I propose that all three interact. First, reintroduction success will be highest for endangered species that share traits with non-rare native species, invasive plants, and species that excel in restoration plantings as reviewed from the ecological literature. Ten traits are identified as common to at least two of these groups. Second, reintroductions will do best in habitats ecologically similar to existing wild populations and with few local threats, such as non-native plants and herbivores. And third, the methods used to establish plants, such as planting seeds vs. transplants or selecting appropriate microsites, will influence outcomes. For any reintroduction project, potential pitfalls associated with a particular species, site, or technique may be overcome by integrating information from all three areas. Conducting reintroductions as designed experiments that test clearly stated hypotheses will maximize the amount and quality of information gained from each project and support adaptive management.