When one thinks of border protection thoughts naturally focus on illegal immigration, drugs, and weapons smuggling. A less often acknowledged but equally critically component of border control involves securing the border from invasive micro-organisms.

At United States ports of entry, the contents of air, maritime, truck, and rail cargo, as well as air passenger baggage, vehicles, and mail are subject to Agricultural Quarantine Inspection (AQI) by the United States Department of Homeland Security (DHS), Customs and Border Protection officials. The purpose of AQI is to help ensure that United States agriculture is protected from accidentally or intentionally introduced pests and diseases, including the possibility of agroterrorism.

Traditionally inspecting cargo shipments of fruits and vegetables at United States ports has been based on inspecting 2% of the items in a container for the presence of pests, with some allowances for the size, contents, and origin of the container.

A new study , Securing the Border from Invasives: Robust Inspections Under Severe Uncertainty, written by two professors at the University of Massachusetts, Amherst, Mass., L. Joe Moffitt and John K. Stranlund, and Craig D. Osteen, an agricultural economist at the United States Department of Agriculture , argues that current systems are outmoded and badly in need of rethinking.∗

“Although simple to apply,” the study says, current inspection rules “appear not to have any economic content; that is, they does not consider the costs of inspections or the losses of failing to prevent an invasive species from entering the country. Nor do they account for the severe uncertainty associated with infestations in shipping containers and the potential losses from introductions of poorly understood or surreptitiously introduced invasive species.”

The authors propose an alternative set of decision criteria for determining inspection probabilities that incorporate economic considerations with particular emphasis on the severe uncertainties of pest introductions and damage.

“With probability distributions over invasive species introductions and their impacts one could cast the problem of determining optimal inspection rules in the familiar terms of risk analysis,” the authors write. “Then it would be relatively straightforward to specify inspections rules that balanced the costs of inspections against the expected benefits of preventing introductions of pests.”

However, the study adds, “this would require information that policy makers don’t possess, cannot obtain at all, or cannot obtain within a timeframe that is useful. In many areas of economic decision making, including the management of invasive species, it is often difficult to measure and interpret probability distributions associated with uncertain outcomes.”

The authors outline an alternative approach known as information-gap (info-gap) decision theory, designed for cases in which probability distributions for uncontrolled events are not available.

“The essence of info-gap analysis,” according to the study, “is the pursuit of decisions that are robust in the sense that, roughly speaking, they maximize the range of uncertainty in the decision environment within which the decision maker is certain to achieve a specified performance requirement. One decision is more robust than another if the range of uncertainty under which the performance requirement is met is larger. Given a performance criterion, a robust decision gives the decision maker maximum confidence that his or her performance criterion will be met.”

Adopting this approach to the problem of determining robust inspection protocols for detecting invasive species in imported agricultural goods, the authors say, involves developing an inspection protocol to maximize the set of uncertain outcomes over which the expected loss from an introduction plus the cost of inspections will not exceed a critical value.

Comparing what they call robust inspection rules to the AQI 2% rule the authors find that “optimal inspection rules provide significant increases in robustness over the AQI rule over a wide range of feasible performance criteria. Moreover, robust inspection rules suggest significantly more scrutiny of incoming shipments than the AQI rule.”

This suggests, concluded the authors, a reallocation of federal resources to more intense inspections and away from efforts to deal with invasives that get through the inspection process.

“For a wide range of performance criteria,” they write, “the 2% rule is simply not very robust to the substantial uncertainty that characterizes the problem of preventing some invasive species introductions.”

Moreover, they add, “ our calculations of robust optimal inspection rules suggests that a shift of resources toward more inspections and away from allocating funds to deal with invasives that get past the inspection process may be justified.”

Increasing the agricultural inspection rate would require congressional action to increase budget appropriations or identify alternative funding sources, the authors acknowledge. It is achievable they believe, despite current fiscal constraints, citing US Government Accountability Office (USGAO) estimates that the current cost of inspecting commercial vessels is considerably less than total fees collected.Since the protocol can be applied to poorly understood or surreptitiously introduced organisms for which probabilities are not easily available, the authors suggest it can address concerns about detecting new pests and agro-terrorism threats during inspection.

“ By suggesting higher sampling rates than currently used under a wide range of performance criteria,” they say, “ the protocol can address concerns about inspection reliability raised by declining interceptions as import shipments increased. Although the study is focused narrowly on the challenge of detecting invasive species in fruit and vegetable shipments, the authors argue that this same approach might be applicable to an increasingly wide range of detection problems where uncertainty is severe and effective use of scarce inspection resources is required. Potentially useful applications of this approach might further include border inspections for smuggled contraband, general law enforcement problems, and the early detection and control of infectious diseases.