The Crisis

Climate change threatens to transform the distribution of our native tree species and the health and composition of our forests. The effects of climate change are expected to lower tree diversity, advance the spread of invasive insects and plants, and shift the range of some tree species. The region’s fragile tree canopy will be further weakened by the impacts of changes in temperature and rainfall patterns and the increased occurrence of extreme weather events.

At the same time that trees will be adversely affected by changes in climate, trees can help slow climate change. Trees can be part of the solution by absorbing the carbon dioxide and greenhouse gases that contribute to global warming, but their potential effectiveness is under-mined by continuing tree loss.

Invasive insects and exotic diseases can decimate tree species that lack defenses against them, as exemplified by the historic loss of the American chestnut and American elm and the more current loss of ash. Devastation of a tree species affects the wildlife that depends on it and also the forests where it grew, as the dead trees open area to invasive species and as gaps in the canopy result in higher stream temperatures that affect aquatic life. The invasive insects of greatest local concern — for either recent or potential impacts — include the following.

Emerald ash borer (EAB) – The EAB has moved through much of the region, left millions of dead ash trees in its wake, and caused millions of dollars to be spent on removing trees from public right-of-ways, parks and other areas where they posed a risk to public safety. The EAB will finish eradicating its host trees in our region within a few years (except for trees chemically treated), but the impacts of this massive tree loss will affect our communities and forests far into the future.

Asian Longhorned Beetle – The ALB poses a deadly threat to over a hundred tree species in thirteen genera – including maple, sycamore and willow. Since the ALB’s discovery in Clermont County in 2011, about a hundred thousand trees have been removed (as of December 2018) and regulations have been imposed to prevent firewood movement and the beetle’s spread beyond a 57-square mile area (East Fork State Park, Tate Township, part of Monroe Township). It’s expected that the ALB will be contained, but if it were to spread unchecked, local tree loss could approach 60% over a 20-30 year period from combined impacts of the ALB and EAB. Learn more about the ALB at Agri-Ohio

Other invasive insects emerging as threats to local trees include:

• Hemlock Wooly Adelgid (HWA) – has killed millions of hemlocks in the Appalachian region, is becoming established in parts of Ohio
• Gypsy Moth –feeds on the leaves of over 300 different tree and shrub species in its caterpillar stage (especially fond of oak), causes permanent damage or death after a couple of years of defoliation
• Spotted Lanternfly – first detected in 2014 in Pennsylvania and expected to enter our region soon (eggs carried by vehicles, firewood, other items that travel long distances); leaves a sticky residue that attracts fungus and mold to a variety of fruit, ornamental and woody trees; research underway to determine whether predation by some native wasps might reduce this invasive insect’s impact
• Walnut Twig Beetle – carries a fungus called thousand cankers disease (TCD) that’s fatal to black walnut trees, identified in Butler County (but no trees yet identified as infected), cited as a serious problem by the Kentucky Division of Forestry
• In addition to TCD, other diseases that are impending threats to local trees include:
  — Beech Leaf Disease (BLD) – a newly observed disease affecting beech trees in northeastern Ohio
  — Oak wilt – a fungus that’s often fatal to oak trees, currently spreading through Ohio and Kentucky

Learn more about invasive pests and diseases at these websites:

• Ohio Division of Forestry: Insects and Diseases
• Ohio State University Extension: Oak Wilt (PDF)
• Kentucky Division of Forestry
• Spotted Lanternfly

Invasive plant species that grow aggressively, spread, and displace native plants are a major factor in the decline of native trees and loss of bio-diversity. Invasive plants of greatest concern locally for their recent or potential impacts include the following.

Bush honeysuckle (Amur and other nonnative bush honeysuckles) is prevalent throughout open and developed areas in our region. The plant has moved from woodland edges into forest interiors and is filling the gaps from downed ash trees. It’s displacing native plants and native habitat, forming dense thickets that halt natural succession and blocking the formation of undergrowth and leaf litter that act to reduce runoff and erosion. The berries of bush honeysuckle are a food source for birds but don’t have the nutritional value to sustain migrating birds. Learn more at
Ohio State University Extension: Controlling Non-Native Invasive Plants in Ohio Forests: Bush Honeysuckle
Indiana Department of Natural Resources: Invasive Plant Species Fact Sheet: Asian Bush Honeysuckle (PDF)

Ornamental or flowering pear (commonly called Callery pear; Pyrus calleryana and ‘Bradford’, ‘Aristocrat’, ‘Cleveland Select’ and all of its other cultivars) is another major impediment to the natural succession of native trees. Ornamental pear has been widely planted in residential areas and public spaces but has spread through cross-pollination to become prevalent in open areas and is now considered an invasive species. As a major threat, flowering pear has colonized vacant lots and open fields, tolerates a wide variety of conditions and is difficult to remove while young. Learn more from the Ohio Division of Forestry

Winter Creeper and English Ivy (Euonymus fortune and Hedera helix) are commonly used as ornamental groundcovers, but they’re also climbing vines that are accelerating the loss of large-canopy and mature trees in our local communities and degrading woodlands and wildlife habitat as well. As climbing vines, winter creeper and English ivy are imminent threats to any tree on which they grow.

These vines can cause the death of mature trees by covering their leaf foliage and blocking sunlight needed for photosynthesis, resulting in tree death by slow starvation. The vines can smother small trees, increase tree vulnerability to damage from insects and storms, and rob older trees of moisture and nutrients through competition among the roots. As a ground cover, the vines in dense mats can prevent tree seedlings from becoming established, or if they cover a tree’s root flares, the vines raise the potential for fungal disease and tree death. You can learn more about these vines at:
Ohio Environmental Council
Greenville News 

To preserve vine-infested trees, vines can be removed by cutting out the portion between the ground and a couple of feet up the trunk (being careful to not damage the bark), allowing the vines to die above the cut, removing the vine’s roots so that a cleared space surrounds the tree trunk, and monitoring to prevent the vine’s resurgence. These sources are helpful for vine removal (information in each of sources can apply to either species).
Olmsted Parks Conservancy: Winter Creeper: How and Why to Remove from Trees (video)
How to kill English ivy

Our region can fight the tree crisis by planting new trees and keeping more of the trees we have, but adequate financial investment is critical for success. Monetary resources are needed not just to restore and expand tree canopy but to provide the kind of tree care and management that will create healthy, long-lived urban forest.

Throughout the nation, research indicates that public investment in urban forestry has declined in recent years, and cities are becoming on average less green. The persistent lack of funding for urban forestry is attributed to budget constraints, competing needs for public funding, and a general unawareness of the financial value of tree benefits. The financial gap between current spending and the investment needed to maintain healthy urban canopy is estimated at $8 per person annually on average. View the full report. (PDF)

National financial assessments don’t apply directly to our region, but it’s clear that local tree programs haven’t kept up with attrition. A failure to allocate adequate funding for tree planting and management is a major threat to achievement of a greener future.

Deer pose another threat to trees and an impediment to reforestation. Through over-population and by grazing on tree seedlings, deer contribute to the lack of saplings in many local wooded areas. In the words of one park staffer: “We don’t have natural forest succession anymore. What winds up coming up are invasive species and the few native plants that deer don’t prefer.”

Development practices are a major contributor to tree loss, especially for the loss of large mature trees and the fragmentation and decrease of forested areas. Loss can occur by removing trees during site preparation or by damage from construction practices. An injured tree may die quickly, or damage can cause a tree’s slow decline and death over a period of years.

Soil compaction is the most common construction practice that’s harmful to trees. Compaction typically results from construction equipment or stockpiled materials,
which have the greatest impact within the dripline. Compaction destroys soil structure by closing the pore spaces through which the tree roots absorb oxygen, water and nutrients, or compaction can crush the roots concentrated in the upper soil levels (may extend beyond the dripline).

Other common construction practices contributing to tree loss are topsoil removal (deprives the roots of vital nutrients) and grading. Grading can cause roots to be severed or smothered; lowering the grade by just two inches eliminates the feeder roots. Tree loss can also occur from damage to the bark or trunk, even though new wood may cover the wound or decay.