Tree infestation is a pressing issue that threatens the health of forests across the United States. Harmful pests and diseases are devastating millions of acres of trees annually, reducing biodiversity and releasing vast amounts of carbon into the atmosphere.
By analyzing important statistics around this topic, we can better understand the severity of these infestations, identify hotspots, and prioritize conservation efforts.
Read on to learn about the latest statistics on the severity of tree infestations in the U.S., the types of invasive species involved, their environmental and economic impacts, and how they contribute to climate change.
Key Takeaways:
- In 2022, 8.4 million acres of U.S. forests experienced tree mortality from insects and diseases, up from 5.8 million acres in 2021.
- 1.4 million street trees are projected to die from invasive pests by 2050, which will cost the U.S. about $30 million annually.
- 41.1% of total live biomass in U.S. forests is at risk from pest species.
- By 2027, 334 million hectares of U.S. forestland will be at risk of tree mortality from insects and diseases.
- By 2027, 25 million hectares of forests in the United States are expected to lose more than 20% of their host tree basal area due to infestations.
- By 2050, the emerald ash borer is expected to destroy 99% of ash trees in over 6,000 communities and cause 90% of insect-related tree damage.
- In 2022, 50% of whitebark pine trees died due to white pine blister rust, impacting 500,000 acres across the country.
- Hemlock Woolly Adelgid (HWA) caused damage to nearly 6,000 acres of hemlocks in the eastern U.S. in 2022.
- Spongy moth defoliation impacted 1.7 million acres of trees in the U.S. in 2022, down from 2.5 million acres in 2021.
- In 2022, the southern pine beetle affected 14,000 acres of trees, with over 9,000 acres impacted in New York.
- Rapid ‘Ōhi‘a Death infested 865,000 acres of trees in Hawaii in 2022, with 618,000 acres on Hawai‘i Island alone.
- The annual carbon sequestration loss due to insect and disease damage in forests equals 50 million tons of carbon dioxide, which is equivalent to the emissions of over 10 million cars.
- Forests damaged by pest infestation in the U.S. sequester 69% less carbon than healthy forests.
Severity of Tree Infestation in the U.S.
- According to the 2022 “Major Forest Insect and Disease Conditions in the United States” report by the U.S. Department of Agriculture:
- In 2022, 8.4 million acres of forests in the U.S. experienced tree mortality caused by insects and diseases, compared to 5.8 million acres in 2021.
- Out of the 462 million acres of forests surveyed, tree defoliation and other types of damage were observed across 5.9 million acres.
- According to a 2022 study by Hudgins et al. titled “Hotspots of Pest-Induced U.S. Urban Tree Death, 2020-2050”:
- 1.4 million street trees are projected to be killed by invasive insects between 2020 and 2050.
- The annualized cost of insect-induced tree mortality is estimated at US$ 30 million.
- Approximately 23% of urban centers will account for 95% of all insect-induced tree mortality.
- Approximately 90% of the damage caused will be attributed to the emerald ash borer, which is expected to destroy 99% of ash trees across more than 6,000 communities.
- According to a 2020 study by Anderson-Teixeira et al. titled “Long-Term Impacts of Invasive Insects and Pathogens on Composition, Biomass, and Diversity of Forests in Virginia’s Blue Ridge Mountains”:
- In the Blue Ridge forests in Virginia, exotic forest insects and pests had affected at least 24% of trees by 2020.
- Exotic forest insects/pests were responsible for 21-29% of biomass losses across forest ecosystems in this region.
- According to a 2019 study by Potter et al. titled “Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts”:
- Approximately 334 million hectares of U.S. forestland are at risk of experiencing tree mortality from insects and diseases by 2027.
- Nearly 25 million hectares of forest are projected to lose more than 20% of the host tree basal area due to infestations.
- Forest insects and diseases affect 419 tree species across the continental U.S. and Alaska, involving 339 identified agents.
- Approximately 228 of surveyed tree species (54%) are infested by at least one exotic insect or disease agent.
- According to a 2019 study by Fei et al. and the Department of Forestry and Natural Resources at Purdue University titled “Biomass Losses Resulting From Insect and Disease Invasions in U.S Forests”:
- 41.1% of the total live biomass in conterminous forests in the United States is at risk of invasion from pest species.
- There are over 450 non-native insect and disease species in U.S. forests, with 83 recognized as causing reportable damage.
- Of the pests studied, the most common types of damaging pests in U.S. forests are foliage feeders, representing 34%.
- According to a 2019 report by Asaro et al. titled “Denser Forests Across the USA Experience More Damage From Insects and Pathogens”, 11-16% of the 881 tree species native to the United States face the risk of extinction, driven by invasive pests and diseases.
U.S. Tree Infestation Statistics by Type of Invasive Species
- According to the 2022 “Major Forest Insect and Disease Conditions in the United States” report by the U.S. Department of Agriculture:
- In 2022, southern pine beetle activity was recorded in around 14,000 acres. Over 9000 acres of tree mortality because of southern pine beetles were reported in New York.
- In 2022, Rapid ‘Ōhi‘a Death infested nearly 865,000 acres of trees statewide, with 618,000 acres occurring on Hawai‘i Island.
- 10 states in the U.S. had suspected cases of Beech Leaf Disease (BLD). In Pennsylvania, 65 of 67 counties were confirmed to have BLD infections.
- Emerald Ash Borer (EAB) was detected for the first time in Oregon in 2022, with 58 confirmed infested ash trees and 120 suspected infestations.
- In 2022, fir engraver beetles caused tree mortality on nearly 3.4 million acres. The highest infestations were found in California, affecting over 28.1 million trees.
- Nationally, spongy moth defoliation decreased to 1.7 million acres in 2022 from 2.5 million acres in 2021.
- In 2022, approximately 50% of whitebark pine trees have died across their range due to white pine blister rust infestation. About 500,000 acres of whitebark pine have been impacted.
- In 2022, HemlockWoolly Adelgid (HWA) caused damage to nearly 6,000 acres of hemlocks in the eastern U.S. in 2022.
- Oak wilt was confirmed in 52 of 55 counties in West Virginia, 66 of 92 counties in Indiana, and 34 of 67 counties in Pennsylvania.
- In 2022, the roundheaded pine beetle caused tree mortality across 4,500 acres in southwest Colorado.
- Spruce beetle activity was observed on 48,800 acres in Alaska, the lowest annual activity since 2015. Up till 2022, spruce beetle infestations had impacted around 1.9 million acres in Alaska.
Impact of Tree Infestation in the U.S. On Climate Change
- A 2021 study by Quirion et al. titled “Insect and Disease Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous United States” looked at the link between tree insect infestation and climate change and found that:
- Forests damaged by insect infestation sequester 69% less carbon compared to undamaged forests.
- Forests affected by diseases sequester 28% less carbon than healthy forests.
- Across the United States, insect and disease damage is reducing the carbon sequestration potential of forests by approximately 50 million tons of carbon dioxide annually, equivalent to the annual emissions of more than 10 million cars.
- According to a 2019 study by Fei et al. and the Department of Forestry and Natural Resources at Purdue University titled “Biomass Losses Resulting From Insect and Disease Invasions in U.S Forests”, the annual carbon storage lost due to forest pest infestations is equivalent to the carbon emissions from 5 million vehicles.
Frequently Asked Questions
What Is Tree Infestation?
Tree infestation occurs when harmful insects, fungi, or other pests invade forests and attack trees. These pests cause problems like defoliation (leaf loss), disease, or tree death. Common examples include bark beetles and the emerald ash borer.
Is Tree Infestation Bad in the U.S.?
Yes, tree infestation is a serious problem in the U.S. Research by Purdue University shows that over 40% of forested land is at risk due to invasive species, which are killing so many trees that about 6 million tons of carbon are released into the air each year.
Which Is the Most Dangerous Invasive Pest to Trees in the U.S.?
The emerald ash borer is considered one of the most dangerous invasive pests in the U.S. This jewel beetle is expected to kill 99% of ash trees and be responsible for 90% of all insect-related tree cover damage by 2050.
