Ecological Impacts of Emerald Ash Borer in Forests at the Epicenter of the Invasion in North America

Abstract

We review research on ecological impacts of emerald ash borer (EAB)-induced ash mortality in the Upper Huron River watershed in southeast Michigan near the epicenter of the invasion of North America, where forests have been impacted longer than any others in North America. By 2009, mortality of green, white, and black ash exceeded 99%, and ash seed production and regeneration had ceased. This left an orphaned cohort of saplings too small to be infested, the fate of which may depend on the ability of natural enemies to regulate EAB populations at low densities. There was no relationship between patterns of ash mortality and ash density, ash importance, or community composition. Most trees died over a five-year period, resulting in relatively simultaneous, widespread gap formation. Disturbance resulting from gap formation and accumulation of coarse woody debris caused by ash mortality had cascading impacts on forest communities, including successional trajectories, growth of non-native invasive plants, soil dwelling and herbivorous arthropod communities, and bird foraging behavior, abundance, and community composition. These and other impacts on forest ecosystems are likely to be experienced elsewhere as EAB continues to spread.

Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts

“…and its relatives across large areas of eastern North America [14]. More recently, hemlock woolly adelgid (Adelges tsugae Annand) is decimating eastern hemlock (Tsuga canadensis (L.) Carriere) across the same area [15]; emerald ash borer (Agrilus planipennis Fairmaire) is effectively eradicating several ash (Fraxinus) species in the north-central United States and southern Canada [16], and laurel wilt disease, involving an introduced insect vector (Xyleborus glabratus Eichhoff) and a pathogen symbiont (Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva), has killed hundreds of millions of redbays (Persea borbonia (L.) Spreng.)…”

First North American record of an unnamed West Palaearctic Agrilus (Coleoptera: Buprestidae) infesting European beech (Fagus sylvatica) in New York City, USA

“…Firstly, since the beginning of the millennium, alien Agrilus are discovered in North America with the scattering rate of one in about every three years (increase from six to 12 by 2019). One of them, A. planipennis, the infamous emerald ash borer, has caused unparalleled economic losses estimated at over 1.6 billion USD in the United States annually (Aukema et al, 2011), ecological impacts (Klooster et al, 2018), and threats to Native American cultural traditions (Costanza et al, 2017), all within about 25 years of establishment (Siegert et al, 2014). It might, therefore, be a matter of time before the sad story of mass North American tree killing is repeated by another immigrant Agrilus.…”

Dynamic Responses of Ground-Dwelling Invertebrate Communities to Disturbance in Forest Ecosystems

“…The range of EAB is increasing rapidly, and because Fraxinus is one of the most widely distributed tree genera in North America, the scale of impact will become continental. Consequently, EAB is causing widespread, nearly simultaneous formation of canopy gaps [91,92], with significant ecological and economic impacts [35,93,94,95]. Individual gaps from EAB-induced ash mortality are relatively small because most ash species exist in diverse forest communities .…”