Restoration and management projects often involve a high degree of uncertainty and risk. One way to minimize uncertainty involved in restoration and management projects is to use small-scale, carefully planned and controlled experiments to inform larger projects. This form of active adaptive management allows investigators and managers to accumulate knowledge by using experiments to test and evaluate particular hypotheses, rather than by accumulating anecdotes generated through trial and error. This knowledge then can be used to alter plans and actions to produce projects with less risk and uncertainty and a higher chance of success.
This presentation describes a case study of an ongoing active adaptive management process at Zion National Park (ZNP). In the 1920s and 1930s, a 4.5 mile section of the North Fork of the Virgin River (NFVR) was lined with revetments to control flooding and protect the newly built road and lodge within the canyon. Eighty years of decreased flood frequency and intensity have resulted in decreased Populus fremontii (cottonwood) and Salix spp. (willow) recruitment and have facilitated the colonization of invasive Bromus tectorum (cheatgrass) and Bromus diandrus (ripgut brome) within the canyon. Loss of native diversity, combined with an increased fire threat due to the fine fuels produced by the grasses have made restoration of the NFVG a priority at ZNP. Restoration efforts are focused on restoring flooding to the canyon bottom and restoring native species to prehistoric (fluvially disconnected) terraces within the canyon.
Preliminary planning exercises for restoration of riparian terraces highlighted many uncertainties surrounding control of the invasive grasses and revegetation of the terraces with native xeroriparian plant species. Rather than using a trial-and-error approach, ZNP staff partnered with academic, government and private-sector collaborators to conduct small scale experiments to explicitly address uncertainties concerning the composition and quality of native seed banks; Bromus spp. biomass removal; herbicide rates and application timing; and effective seeding methods for native species. Active adaptive management has succeeded at ZNP because all stakeholders share a common objective; ZNP managers accept the risk inherent in experimentation; and ZNP personnel are committed to finding funding to continue these projects. Success at ZNP can be used as a template for restoration projects elsewhere, however, other projects may not have the luxury of time that this approach requires, or may be unable to find academic partners due to lack of incentives for this type of research within the academic community.