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Invasive alien forest insects will kill 1.4 million urban trees in US by 2050: Study

  • Published
    19th Mar, 2022

A recent study found that invasive alien forest insects will kill 2.1-2.5 per cent of all street trees (1.4 million) in the United States in 30 years (2020-2050). 


About invasive species:

  • An invasive species is an organism that is not indigenous, or native, to a particular area.
  • Pathways: An invasive species can be introduced to a new area via the ballast water of oceangoing ships, intentional and accidental releases of aquaculture species, aquarium specimens or bait, and other means.
  • Not all non-native species are invasive.
    • For example, most of the food crops grown in the United States, including popular varieties of wheat, tomatoes, and rice, are not native to the region.
  • Features: To be invasive, a species must 
    • It must adapt to the new area easily.
    • It must reproduce quickly.
    • It must harm property, the economy, or the native plants and animals of the region.


  • Extinction of native ecosystem: Invasive species are capable of causing extinctions of native plants and animals, reducing biodiversity, competing with native organisms for limited resources, and altering habitats.
    • This can result in huge economic impacts and fundamental disruptions of coastal and Great Lakes ecosystems.
  • Threat to resources: Invasive species can harm both the natural resources in an ecosystem as well as threaten human use of these resources.
  • Threat to native wildlife: Invasive species are among the leading threats to native wildlife.
    • Approximately 42 percent of threatened or endangered species are at risk due to invasive species.

Key findings of the study:

  • Invasive alien forest insects will kill 2.1-2.5 per cent of all street trees (1.4 million) in the United States in 30 years (2020-2050).
  • This loss would cost $30 million annually to manage.
  • Most of this damage (95 per cent) would be caused in 23 per cent of America’s urban areas.
  • Ninety per cent of all mortality would be due to the emerald ash borer (Agrilus planipennis).
  • The insect is expected to kill almost all the ash trees in 6,000 US urban settings.
  • The emerald ash borer will impact an area of 902,500 square kilometres, mostly in the southern and central US.
  • These areas would witness the destruction of 98.8 per cent of all ash trees.
  • Maple and oak trees would face the threat of Asian wood borers in the future, costing $4.9 billion over 30 years.
  • The study was the first spatial forecast of urban tree mortality due to invasive insect pests done in the US and identified dominant insect pests and spatial impact hotspots.

List of invasive flora and fauna in India


State / Region

Native to

African apple snail

Andaman and Nicobar

Papaya Mealy Bug


Mexico and Central America,

Cotton Mealy Bug


North America

Amazon sailfin catfish

West Bengal

Black Wattle

Western Ghats

South East Australia

Water Hyacinth

It is found throughout India

Tropical America

Black Mimosa

Himalaya, Western Ghats

Tropical North America

Parthenium/ Congress grass, Parthenium

It is found throughout India

Tropical North America

Cannibal Snail / Rosy wolf snail

Native to the southeastern United States.

Indian Bullfrog

Andaman and Nicobar

Afghanistan, Bangladesh, India, Myanmar, Nepal, Pakistan

Lantana camara

In the Bandipur National Park, Karnataka

South America

Additional examples:

  • Cogongrassis an Asian plant that arrived in the United States as seeds in packing material.
  • Feral pigswill eat almost anything, including native birds. They compete with native wildlife for food sources such as acorns.
    • Feral pigs spread diseases, such as brucellosis, to people and livestock. E. coli from their feces was implicated in the E. coli contamination of baby spinach in 2006.
  • European green crabsfound their way into the San Francisco Bay area in 1989. They out-compete native species for food and habitat and eat huge quantities of native shellfish, threatening commercial fisheries.
  • Dutch elm disease(caused by the fungus Ophiostoma ulmi) is transmitted to trees by elm bark beetles. Since 1930, the disease has spread from Ohio through most of the country, killing over half of the elm trees in the northern United States.
  • Emerald ash borer beetles: Emerald ash borer beetles are invasive insects first discovered in Michigan in 2002 and most likely brought over on packing material from East Asia.

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