Healthy Forests Require Deer Control

If left unchecked, both overabundant white-tailed deer populations and invasive shrubs like Amur honeysuckle (Lonicera maackii) can devastate deciduous native tree regeneration. Yet, a management strategy focused only on deer, or only on invasive shrubs, results in little or no forest health improvement, according to research from Ohio, spanning more than 10 years.

“Control of only invasive shrubs will reduce native cover and not improve tree regeneration,” says David Gorchov, PhD, and Miami University (Ohio) biology professor. “Managing only deer will increase woody plants but reduce native cover. Management of both stressors is needed to promote tree regeneration and plant community restoration.”

These conclusions summarize research, recently published online in Invasive Plant Science and Management (IPSM), volume 17, issue 1, by Cambridge University Press, a Weed Science Society of America (WSSA) research journal. For this study, Gorchov and his coauthors, MS student Marco Donoso and undergraduate honors student Hanna Leonard, investigated deer pressure and Amur honeysuckle effects for 11 years in a split-plot experiment in the Miami University Natural Areas in southwest Ohio, where both were at high density.

To conduct the research, Gorchov and another Miami University biology professor, Tom Crist, PhD, established deer exclosure (an area from which unwanted animals are excluded) and deer access plots in 2010, and removed invasive honeysuckle in each plot half.

“Excluding deer, but not removing honeysuckle, significantly increased the density and species diversity of tree seedlings,” says Gorchov. “However, for some tree species – Sugar Maple, Red Oak, Bitternut Hickory, Black Cherry, Redbud – the combination of deer exclosure and shrub removal was necessary to enhance abundance, though that same combination allowed some invasive plants, like Burning Bush and Winter Creeper, to thrive.”

Forest regeneration failure means insufficient juvenile tree density to replace canopy trees. “We found that tree seedlings responded more to deer exclusion than to Amur honeysuckle removal, but combining both measures results in the greatest tree seedling density and species richness,” points out Gorchov.

“Managing both deer and invasive shrubs is necessary to realize the greatest improvement in tree seedling density and diversity and recruitment of trees from seedlings to the understory-size class, as well as cover of native plants.”

White-tailed deer and invasive shrubs that deer find palatable are commonly found in high densities in deciduous forests in the eastern and midwestern United States. As a result, these findings will help to inform forest managers throughout the region about successful practices to help forests thrive.

Reference: Zalewska K, Gilroy JJ, Catry I, et al. European Breeding Bird Declines Associated With Narrower Climatic Niches. J Biogeo. 2025. doi: 10.1111/jbi.15127

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