The Threat of Invasive Species
One of the biggest threats to trees and forests today is invasive insect species. In particular, the emerald ash borer has become a major problem across North America. This small metallic green beetle native to Asia first arrived in the United States in the 1990s through shipping pallets. It likely went undetected for several years before being officially identified in Michigan in 2002. Since then, the emerald ash borer has spread to 35 states and several Canadian provinces, decimating ash tree populations along the way.
The larvae of the emerald ash borer feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. This eventually kills the tree, usually within 2–4 years of infestation. Adult beetles emerge in spring and summer to mate and lay eggs on ash bark. The larvae then tunnel and feed under the bark through fall and winter.
Since its accidental introduction, the emerald ash borer has spread rapidly and killed hundreds of millions of ash trees in forests, cities, and neighborhoods. It threatens all species of North American ash trees.
The Impact on Forests
The emerald ash borer poses a significant threat to forests, especially in areas where ash trees make up a major component of the canopy. Ash trees are ecologically and economically important, providing timber, wildlife habitat, shade, and aesthetic value. When ash trees are killed and removed from the forest ecosystem, it can have cascading effects.
Ash trees represent up to 30% of trees in some North American forests, particularly in the Midwest and Northeast. As ash trees are removed, forest composition is radically altered. This allows other tree species like maples, oaks, and hickories to increase in abundance and fill the canopy gap. The changing forest structure impacts wildlife that rely on ash trees for food and shelter. Water and nutrient dynamics may also shift.
Consequences for Cities and Homeowners
The loss of ash trees in cities and neighborhoods also comes at a high cost. Municipalities must dedicate substantial resources to removing dead and hazardous trees along streets and in parks before they pose a public safety risk. Homeowners are faced with the expense of treating or removing dying ash trees on their property.
Fallen ash trees can damage houses, vehicles, and infrastructure. Cities can lose up to 20% of their tree canopy as ash succumb to the borer. This reduces energy savings from shade, lowers property values, and detracts from community aesthetics. Urban forests become less diverse as ash trees are lost.
Management Efforts
Government agencies like the USDA Forest Service and EPA, as well as conservation groups, are working to slow down the spread and minimize the impact of the emerald ash borer. Efforts include quarantines, insecticide treatments, biological control methods, and public education campaigns.
Quarantines aim to slow long-distance spread of the borer by regulating movement of ash wood products and nursery stock out of infested areas. Systemic insecticides can be injected or drenched into ash trees to protect high-value urban trees. Several natural enemies of the borer from China have been introduced as biological controls, with some success in establishment.
Researchers are also working to better understand emerald ash borer biology, develop new management techniques, and breed ash trees resistant to the borer. However, controlling this invasive pest remains very difficult.
Looking to the Future
The battle against emerald ash borer is likely to continue for many years. Several options are being considered for the long-term management of ash forests. These include planting alternative native tree species, exploring genetic biocontrol methods, and conserving ash tree genetic material for future restoration efforts.
We must also continue to support research and conservation efforts focused on emerald ash borer and other invasive forest pests. Although we will lose many ash trees, innovative management solutions may help conserve ash on the landscape. Public education is key to preventing further spread. With dedication and creativity, we can hopefully find sustainable ways to manage invasive species threats to our forest ecosystems.
The Emerald ash borer in Utah is an issue of rising concern as infestations move closer to the state. Proactive management will be critical to protecting Utah’s ash resources.
