Non-Native Forest Insects and Pathogens in the U.S.: Impacts and Policy Options

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Scientists from the Hubbard Brook and Harvard Forest LTER sites led a team of ecologists, economists, and policy experts in an initiative to review and synthesize information on invasions of non-native forest insects and diseases in the US, including their ecological and economic impacts, pathways of arrival, distribution within the US, and policy options for reducing future invasions. Non-native insects have accumulated in US forests at a rate of about 2.5 y^-1 over the last 150 y. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates.  Introduced pests occur in forests and cities throughout the US, and the problem is particularly severe in the Northeast and Upper Midwest. More than 24 million hectares of forestland in the US are estimated to be at risk of significant loss of host tree basal area from non-native pests in the next 15 years.

Non-native forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from US forests in the span of decades. The resulting shift in forest structure and species composition alters ecosystems functions such as productivity and nutrient cycling and may degrade wildlife habitat.  In urban and suburban areas, loss of trees from streets, yards and parks affects aesthetics, property values, shading, stormwater runoff, and human health.  The economic damage from non-native pests has yet to be fully reckoned, but is in the billions of dollars per year, and the majority of this economic burden is borne by municipalities and residential property owners.

Current policies and protocols for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. All of the lines of defense against pest arrival and establishment need strengthening, including pre-arrival measures, phytosanitary treatments to ensure clean shipments of plants and wood products, inspections at ports of entry, post-entry measures such as quarantines, and surveillance and eradication programs.  Improved data collection procedures for inspections and greater data accessibility would support better evaluation of policy effectiveness.  Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions.