Assessing ecologic and economic impacts of non-native forest insects and diseases: White pine blister rust as a case study

Background/Question/Methods It is widely recognized that nonnative forest insects and diseases cause substantial adverse ecological effects and, subsequently, decrease the value of ecosystem goods and services.  However, despite general agreement about the nature of these impacts, there has been limited attempt to quantify their magnitude on particular ecosystem components, or synthesize information about their cumulative effects.  Faculty and students from seven universities synthesized data on ecologic and economic impacts of forest invaders through a Distributed Graduate Seminar sponsored by the National Center for Ecological Analysis and Synthesis.  As part of this effort, we used white pine blister rust (Cronartium ribicola) - one of the most well studied nonnative forest pathogens in North America – as a case study for examining the quantity and quality of published information on the ecological impacts of nonnative forest insects and diseases, in order to determine whether there is sufficient ecological information to model non-market economic costs.  We identified a total of 364 articles published between 1960 and 2007 on white pine blister rust by searching Web of Science - Science Citation Index and Agricola.  For each article, we collected data on 74 variables, including geographic location of the investigation, primary research objective, Pinus host species, and measures of ecologic or economic impact. 
Results/Conclusions We found that publication rate increased with time, with the last decade accounting for 33% of all published articles.  Sixty percent of papers addressed the basic biology of white pine blister rust.  Other dominant research objectives included resistance breeding (27%) and identifying infection rates and distribution (15%).  However, only eight papers (3%) addressed ecological impacts of white pine blister rust, and three of these were review articles.  Interestingly, only one article mentioned the impact of climate change on white pine blister rust; similarly, the effect of rust on fire dynamics was investigated in only one paper.  The majority of articles focused on three commercially valuable Pinus species, rather than species without commercial value (76 vs. 24%), respectively).  These findings suggest that our understanding of the ecological effects of white pine blister rust is extremely limited.  Given that blister rust has received more scientific attention than most other non-native forest pests and pathogens in North America, we suspect that there is even less ecological information for other species of concern.  In order to quantify non-market economic costs of nonnative invasive forest pests and pathogens, there must be greater investment in research on their ecological impacts.