Adaptive management of geese in a restored tidal freshwater wetland.

Failure to account for top-down control on vegetation dynamics can strongly influence restoration trajectories. Abundant (large) herbivores can impede restoration efforts by exerting intense grazing pressure on plant communities. An adaptive management cycle can mitigate initially discounted impacts and alleviate herbivore disturbances. In this study, conducted in an urban and restored tidal freshwater wetland in Washington, D.C., we tested the effects of resident, non-migratory Canada geese (Branta canadensis maxima) in a long-running exclosure study (2009-2025), with vegetation monitoring of paired herbivore exclosure and unprotected control plots both before and after implementation of adaptive management in the form of goose population control. Unprotected plots recovered strongly several years after goose population control measures were initiated. Specifically, total plant cover, cover of annual species, species richness, and Shannon-Wiener Diversity Index increased in response to goose population control. In most regards, unprotected control plots began to resemble herbivore exclosure plots following enactment of goose population control activities. However, community composition was slower to recover and lagged other metrics. Surprisingly, the overall trajectory of recovery continues to be influenced by the initial vegetative state in which the plots occurred when the experiment was begun in 2009, reflecting a long legacy within the plant dynamics. These results highlight the effectiveness of localized population control for non-native or otherwise problematic herbivores in a restoration setting and the value of adaptive management for restoration success.