Invasive insects cause tens of billions in damage


Formosan subterranean termite damage to a house in New Orleans; observed by Ed Freytag & Alan Lax; photo by Scott Bauer, USDA Agricultural Research Service;

A recent study documents the high costs imposed by invasive insects worldwide.  The study, by Bradshaw et al. (source with link is at the end of this post) concluded that invasive insects cause at least $77 billion (US) in damage every year. This figure includes costs of $70 billion in estimates of damaged goods and service; and $6.9 billion in associated health costs.

What is more, this figure is “grossly underestimated” for a number of reasons:

  • There were few studies providing cost estimates. The authors started by reviewing more than 700 articles, but found that only 158 yielded usable economic estimates.
  • Most of the studies applied to North America and Europe; much of the globe is not included.
  • Ecosystem services eroded by invasive pests are rarely quantified.
  • The health cost estimate does not include the impact of malaria (in most areas, the vector is native rather than invasive), the Zika virus, or economic losses in tourism or productivity (these latter were too difficult to calculate).

While the most destructive of the insects identified in the reports was the Formosan subterranean termite, Bradshaw et al. question some of the economic data included in the single report on the termite. The most damaging insect for which they found “reproducible” economic estimates is the diamondback moth, a voracious consumer of cruciferous crops worldwide.

Other invasive insects cited as being associated with high damage levels are tree-killing pests familiar to readers of this blog: the brown spruce longhorn beetle, the European gypsy moth in North America, and the Asian longhorned beetle (write-ups on all three species can be read here. In my view, the high ranking of these insects reflects a (welcome!) effort by researchers to quantify tree pests’ impacts; although damages caused by agricultural pests are more easily reduced by pesticide applications.

The situation is likely to worsen in the future. According to the authors, climate change, rising human population densities, human mobility, and intensifying international trade will allow these costly insects to spread into new areas. Still, substantial savings could be achieved by increasing surveillance, containment and public awareness (my emphasis).

In an interview with Agence France Presse, one of the coauthors, Franck Courchamp said the best way to combat this growing threat — spread mainly through international commerce — is not more pesticides. Instead, “The solution is better ‘bio-security’,” he said. “This includes inspection of ship and air cargo from certain regions, legislation to ensure that high-risk imports must be treated and rapid eradication of new incursions.” (Interview is posted at



Bradshaw, C. J. A. et al. Massive yet grossly underestimated global costs of invasive insects. Nat. Commun. 7, 12986 doi: 10.1038/ncomms12986 (2016). (Open access)

Posted by Faith Campbell

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