An End to the American Beech?
Last week, in the cool of the July morning, I went for a walk along the Plateau Trail on the western slope of the Cuyahoga Valley National Park. Located a few miles southwest of Peninsula, the Plateau Trail is an easy 4.4-mile loop trail featuring young and older-aged hardwood forest. Along the way, however, I noticed that the leaves of some juvenile beech trees looked unusual. They were dry and crackly, like a brown dehydrated fallen leaf in November, but still green and connected to the tree. I did some research, and it seems that these are among countless other Northeast Ohio beech trees suffering from Beech Leaf Disease.
According to the Ohio Department of Natural Resources, Beech Leaf Disease (BLD) was first discovered in Lake County, OH in 2012, affecting primarily American beech (Fagus grandifolia) and European beech trees (Fagus sylvatica). Since then, BLD has been documented throughout Northeast Ohio and in Pennsylvania, West Virginia, New York, Connecticut, Massachusetts, and Ontario. The ODNR describes, “dark banding on leaves, leaf disfigurement, and branch dieback,” as typical BLD symptoms, “linked to the presence of nematodes (microscopic worms) in the leaves and buds.” BLD has greatly weakened the beech understory and has led to, “extensive mortality” of young beech trees. Many details pertaining to the origin and spread of BLD are still unknown.
Upon discovery, Lake Metroparks Naturalist John Pogacnik contacted the U.S. Forestry Services and botanists at the Ohio State University and others in Europe and Asia regarding BLD. No one else had ever heard of such a disease. Meanwhile, BLD was spreading from just 510ha of Lake County forest in 2013 to 2,525ha in 2016. Similar growth patterns are visible throughout other affected areas. BLD, however, is not the only disease affecting beech trees. Beech bark disease (BBD), spread by the scale insect (Cryptococcus fagisuga), is a lethal disease that, “precedes the attack of the BBD bark fungi” (Ewing, Hausman, Pogacnik, Slot, Bonello, 2019). Additionally, the invasive beech leaf-mining weevil (Orchestes fagi) has been destroying American beech trees in Nova Scotia with greater intensity since 2012. Scientists predict that, through human-assisted and natural movement patterns, O. fagi will spread throughout the existing range of the American beech, causing irreparable damage to the species and North American forests.
Beech-maple forests are an extremely important ecosystem throughout eastern North America. Beech trees, which hold their leaves all winter long, are critical for birds and mammals that rely on them for food and shelter. The migratory red bat (Lasiurus borealis) hides among the beech leaves when it returns to Ohio in early spring. Beechnuts are an integral element in the diets of turkeys, jays, squirrels, foxes, and black bears. Furthermore, the reduction of the beech tree canopy and understory affects the light environment in forests which may greatly alter the entire eastern hardwood ecosystem. The loss of American beech trees will also be expensive to humans, leading to over $225 million lost in terms of the environmental benefits otherwise provided by existing beech trees. Although scientists are not expecting the total extinction of the American beech, its functionality as a species in eastern forests will likely wane.
In the wake of the loss of American chestnut trees (Castenea dentata) eradicated by the chestnut blight of the early 1900s, eastern forests evolved to the now dominant beech-maple ecosystem. Although many species which depended upon chestnut trees did not survive, forest ecosystems adapted just like they have for millennia. If North America does witness the end of the era of the American beech, a new ecosystem will eventually form, and forest species will largely adapt to the new forest composition. The ever changing eastern hardwood forest will persevere as always and, in the meantime, scientists will continue researching ways to stop the spread and defend against BLD and other diseases affecting American beech trees. Next time you’re hiking in the forest and notice a healthy American beech tree, savor the sight and appreciate the beech-maple forest through which you’re likely traversing. You are experiencing a constantly changing environment that never stagnates, one who's days might be numbered.
Image Descriptions: All images taken along the Plateau Trail, Cuyahoga Valley National Park, Peninsula, OH.
Top left: The Plateau Trail winding through the Northeast Ohio hardwood forest
Top middle: American beech trees looking up
Top right: American beech trees looking up
Bottom left: Individual American beech with apparent effects of BLD. Dry ribbed leaves
Bottom right: Closer analysis of aforementioned individual with apparent effects of BLD
Ewing, C. J., Housman, C. E., Pogacnik, J., Slot, J., & Bonello, P. (2018). Beech Leaf Disease: An Emerging Forest Epidemic. ms, Columbus, OH. https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/efp.12488.
Martin, D. K., & Volk, D. (2021, January). Beech Leaf Disease. Pest Alert. https://ohiodnr.gov/wps/wcm/connect/gov/1b6ef179-92be-49d6-ab38-74ecda2ed5c5/BeechLeafDisease-USDA-FS-PestAlert-2021.pdf?MOD=AJPERES&CONVERT_TO=url&CACHEID=ROOTWORKSPACE.Z18_M1HGGIK0N0JO00QO9DDDDM3000-1b6ef179-92be-49d6-ab38-74ecda2ed5c5-nEQ-fsc.
McCarty, J. F. (2017, December 10). Beech Leaf Disease Discovered in Lake County, Spreading Throughout NE Ohio, PA, NY, Ontario: (photos, video). The Plain Dealer. https://www.cleveland.com/metro/2017/12/beech_leaf_disease_discovered.html.
Stansberry, M. (2018, October 26). A Tree Hugger's Guide to the Forest Dynamics of Northeast Ohio. Belt Magazine. https://beltmag.com/a-tree-huggers-guide-to-the-forest-dynamics-of-northeast-ohio/?fbclid=IwAR1s5hrDX732x6ucIN_HQfOJbNaQW-HClpFo-fC9h70eOF3xla5FHaEkAco.
Sweeney JD, Hughes C, Zhang H, Hillier NK, Morrison A and Johns R (2020) Impact of the Invasive Beech Leaf-Mining Weevil, Orchestes fagi, on American Beech in Nova Scotia, Canada. Front. For. Glob. Change 3:46. doi: 10.3389/ffgc.2020.00046