Prioritizing Invasive Species Threats Under Uncertainty

Agricultural and Resource Economics Review, Apr 2006 by Moffitt, L Joe, Osteen, Craig D

Prioritizing exotic or invasive pest threats in terms of agricultural, environmental, or human health damages is an important resource allocation issue for programs charged with preventing or responding to the entry of such organisms. Under extreme uncertainty, program managers may decide to research the severity of threats, develop prevention or control actions, and estimate cost-effectiveness in order to provide better information and more options when making decisions to choose strategies for specific pests. We examine decision rules based on the minimax and relative cost criteria in order to express a cautious approach for decisions regarding severe, irreversible consequences, discuss the strengths and weaknesses of these rules, examine the roles of simple rules and sophisticated analyses in decision making, and apply a simple rule to develop a list of priority plant pests.

Key Words: invasive species, decision criteria, uncertainty

The U.S. Department of Agriculture (USDA) and the U.S. Department of Homeland Security (DHS) have programs to prevent or respond to the entry of damaging exotic pests or invasive species, which are non-native organisms that cause damages in excess of benefits. Program officials make important preparedness decisions concerning many organisms, such as whether or not to collect more information about specific organisms and their potential effects; implement surveillance programs; develop management practices or strategies; ban or restrict imports; require import inspections or treatments; implement offshore management programs; develop plans for eradication, containment, or control strategies in response to pest detections; or implement information or extension programs to help growers identify and respond to a pest. Officials with constrained budgets may have to make rapid decisions under extreme uncertainty. For these reasons, prioritizing invasive species threats and responses is an important resource allocation issue for government decision makers.

Different economic approaches can be applied to decisions concerning invasive species threats, ranging from sophisticated models that consider spatial, dynamic, stochastic, and other aspects of economic and biological systems, to simple decision rules using minimal information. Both sophisticated models and simple rules can have roles in decision making, depending on the decision to be made, available information, and time available for data collection and analysis. We develop a group of simple decision rules that use minimal information, discuss the strengths and weaknesses of those rules, examine potential roles for different rules in decision making, and apply a simple rule to develop a list of priority plant pests for preparedness activities.

In developing the simplified decision rules, we use the minimax criterion as a way to express a cautious approach for decision making, which Horan et al. (2002) suggest decision makers use for uncertain invasive species events with potentially severe, irreversible consequences. The relative cost criterion as applied in the economics of terrorism literature provides insight when there are severe uncertainties about the effectiveness of prevention and response options. Since government officials sometimes use a cautious approach for decision making under uncertainty, the economic implications warrant examination. For example, Michael Chertoff, Secretary of DHS, said that while the Department's risk analysis is based on threat, vulnerability, and consequences, "DHS will concentrate first and most relentlessly on addressing threats that pose catastrophic consequences" (Chertoff 2005).

Context of the Decision Problem

Prioritizing pests or invasive species generally focuses on identifying and ranking the worst threats. The National Invasive Species Council (2003) discussed guidelines for early detection and rapid response systems and cited the need for active detection networks to focus on high-priority species, pathways, and at-risk sites, and for preliminary risk assessment of high-priority species before detection in order to facilitate rapid response after detection. USDA's Animal and Plant Health Inspection Service (APHIS) annually prioritizes plant pests for the Cooperative Agricultural Pest Survey (CAPS) in order to allocate detection and surveillance resources to the greatest threats, using criteria for potential entry, establishment, spread, economic impact, and non-economic impact. Homeland Security Presidential Directive-9 (HSPD-9), in 2004, directed USDA, in coordination with other agencies, to develop a National Plant Disease Recovery System (NPDRS) in order to respond to high-consequence diseases of economically important crops by identifying pest control measures and developing emergency plans for their use.

From an ideal economic perspective, decision makers would consider the costs of prevention or management options and their effects on pest damages, simultaneously select the best approach for every pest, and allocate funds to pests and actions, subject to a budget constraint. However, decision makers often face extreme uncertainty, that is, sparse or unreliable information, about new pests, some of which may be imminent threats, and/or response options. There may be incomplete information about what crops a pest might damage, potential for entry, potential damage, crop area at risk, rates of increase and spread, and environmental and economic factors affecting entry, spread, and damage. In the most extreme cases, the identity of an organism as a pest may be uncertain, because there are undiscovered organisms that may become pests in new environments, while some known organisms, benign in their native environments because natural enemies or production practices mitigate infestations or damage, may cause significant damage in new environments. There also may be incomplete information about the cost-effectiveness of preventative or management methods for some pest threats, and in some cases, those options may be poorly understood or not available. Uncertainty about the likelihood and economic consequences of pest events hinders accurate assessment of threats, while uncertainty about the costeffectiveness of prevention or management options hinders selection of a strategy. When detection or control methods are not available or are poorly understood, none can be selected.