A tree stands still in a crisp October forest. Its stubby height allows it to stand out amongst the array of neighboring oaks and pines and the sun casts a dusty glow on the few leaves that remain on its sturdy branches. Most of the leaves are scattered on the ground, sprinkling an occasional flash of gold throughout the surrounding collage of soil, dead leaves, and pinecones. Meet the ash tree, an extraordinary tree threatened with extinction.
The fraxinus excelsior, more commonly known as the ash tree, is an umbrella term for many different species of ash, the most common species being the green, white, black, blue, and Carolina ashes.
The ash tree has a notable ecological and commercial value. The wood is durable and flexible, making it ideal for interior paneling of houses and the construction of staircases, furniture, and everyday items such as sports equipment and hardware tools. Aside from its basic role maintaining the biodiversity of forests and purifying the air through the process of photosynthesis, countless bird species such as owls, woodpeckers, and redstarts rely on its intricate arrangement of branches as an ecological niche, and some bat species nest in the roots.
The tree also serves as a crucial food source, as many caterpillars consume its nutrient-dense leaves. Even after it decomposes, beetles dwell in the deadwood, and the nutrients are immediately recycled back into the soil to help maintain an adequate level of acidity. However, the recent introduction of an invasive species that preys on the bark of these trees has brought about mass destruction to the unique tree species, and the surrounding environment. The emerald ash borer, or the EAB, is known for its multicolored coat paired with green shimmering wings. They are hard to spot, as they only grow up to half an inch long, but the threat they pose is insurmountable. Native to Northeast Asia, the EAB was first identified in Detroit, Michigan in 2002 after entering the United States via planes and cargo ships.
An infestation begins when an emerald ash borer lays eggs among the tree bark. The beetle’s life cycle commences in the early spring after it hatches from an egg and burrows into the tree, leaving behind an S-shaped tunnel. The larvae feast on the phloem, a key component of the tree’s circulatory system that transports vital nutrients such as water, sugars, and amino acids throughout the ash tree, before exiting the tree as adults. This deprives the tree of essential nutrients, commencing a slow death, many dying only two years after the feeding and hatching cycle begins. The beetles leave the tree as adults, a year or two after they have hatched and created damage that has manifested in the form of physical markers, including peeling bark, dark spots, and S-shaped indents. There are, however, various treatments available to help combat the extinction of the ash tree, such as chemical treatments and the introduction of predators. These insecticides, found in the forms of sprays or injections, can be applied directly to the tree or to the surrounding soil. The beetle itself may be treated with insecticides which prevent them from laying eggs, so they are less likely to enter the tree to begin with. Although these treatments are mostly effective, they cannot keep up with the rate at which the emerald ash borer is destroying ash trees.
By far, the most significant threat of the emerald ash borer is that it feeds on any species of the ash tree and uses its structures to continue its life cycle. Unlike many other invasive species, the EAB has only one native predator, woodpeckers. This, too, is not enough to prevent it from rapidly spreading across the country. In fact, woodpeckers further damage ash trees by drilling holes into infected regions in order to consume the residing beetles.
Once done, the damage created by the EAB is irreversible, and in many cases, the tree must be cut down and removed from the environment.
As of today, The United States Department of Agriculture (USDA) reports that emerald ash borers have killed roughly 15 million ash trees. So far, this has cost the United States up to $25 billion dollars in tree replacement costs, and resulted in a nationwide shortage of ash wood in woodworking.
The future of the ash tree is grim. As of today, roughly 15 million trees have been killed by the EAB, and the available treatment options are still not enough to save the tree. The current rapidly changing ecosystem has brought about even more uncertainty about the threat of the emerald ash borer and future of the ash tree.
Increasing temperatures worldwide have only amplified the problem, as the emerald ash borer cannot withstand frigid temperatures. Therefore, as the number of cold days decreases, the EAB will continue to thrive. The predicted decline in the number of ash trees will only worsen the issue of climate change, as less trees are present to remove carbon dioxide from the atmosphere and provide shade for neighboring plants. When dead trees fall and are not removed from the area, the highly flammable deadwood serves as excellent kindling for forest fires. The more deadwood present, the easier it is for a fire to spread, and other trees to burn down, which emits smoke into the atmosphere and demolishes the population of other vital tree species.
To me, one of the most remarkable parts of the ash tree is the splash of brightness it adds to the fall foliage. Ash trees are known for their leaves that turn a stunning shade of yellow in the fall, the color being visible amongst surrounding trees–even from miles away. With their disappearance, there has been a reduction in the distinct yellow of the ash tree in autumn landscapes, changing the display of vivid colors into muted shades of red and brown.
The emerald ash borer is unfortunately only one of the many risks to the environment and tree species worldwide. The issue of climate change has led to the introduction of countless invasive species that pose a major threat to numerous tree species throughout the United States and the world. Organisms such as the spotted lanternfly, box tree moth, and the elm bark beetle are responsible for the mass deaths of countless trees. Due to steadily rising temperatures, these species have migrated to environments more suitable for them. With very few natural predators in the new area to curb the threat, these organisms are able to thrive in new areas while preying on native species.
Though severely threatened, ash trees can still be saved. Today, there are things that nearly anyone can do to help save this unique species. If you have ash trees on or near your property, and are able to do so, closely monitoring their risk for EAB is crucial for their survival. The first step in this process would be to check your tree for signs of damage, and if there are visible signs, get them tested for ash borer infestation.
If an infestation is present, look into injections or other possible treatments as soon as possible. Even if a tree appears healthy, it is still important to regularly spray ash trees with pesticides to minimize the risk of your tree being affected.
Overall, spreading awareness about invasive species and finding any way–no matter how small–to reduce your carbon footprint is something that anyone can do to combat the threat of not just the emerald ash borer, but any invasive species.
The future of the ash tree is grim. As of today, roughly 15 million trees have been killed by the EAB, and the available treatment options are still not enough to save the tree. The current rapidly changing ecosystem has brought about even more uncertainty about the threat of the emerald ash borer and future of the ash tree.