DOI: 10.13020/de0y-6p48
title: Biological control benefit-risk analysis; Heimpel et al. Ecological Applications

description: The release of biological control agents has been an important means of controlling invasive species for over 150 years. While these releases have led to the sustainable control of over 250 invasive pest and weed species worldwide, a minority have caused environmental harm. A growing recognition of the risks of biological control led to a focus on risk assessment beginning in the 1990s along with a precipitous decline in releases. While this new focus greatly improved the safety of biological control, it came at the cost of lost opportunities to solve environmental problems associated with invasive species. A framework that incorporates benefits and risks of biological control is thus needed to understand the net environmental effects of biological control releases. We introduce such a framework, using native biodiversity as the common currency for both benefits and risks. The model is based on interactions among four categories of organisms: (i) the biological control agent, (ii) the invasive species (pest or weed) targeted by the agent, (iii) one or more native species that stand to benefit from the control of the target species, and (iv) one or more native species that are at risk of being harmed by the released biological control agent. Conservation values of the potentially benefited and harmed native species are incorporated as well, and they are weighted according to three axes: vulnerability to extinction, the ecosystem services provided, and cultural significance. Further, we incorporate the potential for indirect risks to native species, which we consider will result mainly from the ecological process of agent enrichment that may occur if the agent exploits but does not control the target pest or weed. We illustrate the use of this framework by retrospectively analyzing the release of the vedalia beetle, Novius (= Rodolia) cardinalis, to control the cottony cushion scale, Icerya purchasi, in the Galapagos Islands. While the framework is particularly adaptable to biological control releases in natural areas, it can also be used in managed settings, where biological control protects native species through the reduction of pesticide use.
description: This excel spreadsheet allows calculation of the Benefit-Risk Index (BRI) that is described in the manuscript.
Users can input values corresponding to Table 3 in the main text to calculate the BRI and all the requisite functions.
While the spreadsheet is configured for two species of beneficiary and non-target species, users can add rows corresponding to more species of either type.

Note that if a target species is associated with different values of I(tar), Ps(tar) or Pe(tar) in different habitats (e.g. on different host plants), some modification will be needed.

Users are encouraged to contact George Heimpel with any question (heimp001@.umn.edu).

R code for the equations and sensitivity analyses described in the paper. Users should feel free to use the code to extend sensitivity analyses if they wish. They should also feel free to contact George Heimpel (heimp001@umn.edu) if they have any questions.