RAPID: Does riparian vegetation state mediate consequences of climate change-induced extreme flooding for stream-riparian food webs and communities?

Idaho State University, Pocatello ID

Investigators

Abstract

In June 2022, Northern Yellowstone National Park experienced rain-on-snow events leading to a 1 in 500-year flood, devastating local infrastructure and capturing public attention as a high-profile consequence of human-caused climate change. Extreme disturbances, whether they be category 5 hurricanes, severe wildfires, or extreme droughts, are becoming more frequent and intense. Natural resource managers and policy makers need to understand the consequences of such extreme disturbances and find ways to support ecosystem resiliency. Historically, ecologists thought that though ecosystems were resilient to, or even benefitted from, mild or moderate disturbances, extreme disturbances “reset” ecosystems to some uniform, baseline state. NSF has approved RAPID support for this project, to evaluate extreme disturbance in the context of Northern Yellowstone. The study area contains considerable biodiversity throughout a mosaic of distinct habitats. One source of this complexity comes from the restoration of predators like wolves and grizzly bears, their interactions with herbivores such as elk and bison, and the subsequent changes to plant communities. As a result, willows and alders have regrown around some streams and rivers while others, just miles away, remain dominated by grasses and sedges. Previous investigations showed that different plant communities influence the diversity and productivity of streams and rivers, but in ways mediated by local context that result in a mosaic of ecosystem states. Just as the restoration of predators has not uniformly changed this ecosystem, responses to the recent extreme flooding may have been mediated by local context. In turn, results from this study may inform management decisions and influence public perceptions regarding consequences of such disturbances, as indeed past ecological studies have done for wildfire in this region. Through the opportunistic use of a natural experiment and by comparing stream-riparian ecosystems before and after the extreme flooding, this project will evaluate whether a homogenous “reset” of stream-riparian ecosystems occurred, or if terrestrial wildlife dynamics that influence riparian vegetation state, as well as pre-flood traits of aquatic communities, mediated heterogeneous responses of stream-riparian organisms and ecosystem processes. This project will collect parallel measurements after flooding to those collected before, including stream-riparian habitat characteristics, herbivory and riparian plant community composition and structure, stream ecosystem organic matter dynamics, productivity and food web interactions of aquatic invertebrates and fish, and riparian spider and bird communities. If organism, community, or food web traits shape resistance, resilience, and trajectories of change following the extreme flood, this will provide an opportunity to evaluate how such “ecological memory” constrains responses to future extreme events. If traits of organisms and communities are indeed important to mediating responses to extreme disturbances, this project may highlight the importance of conserving such complexity in the face of climate change and the biodiversity crisis. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.