Section 4 outlines the key components of pest risk analysis and explains its growing importance to plant health in general and in managing invasive alien species. It covers the revision of an international standard for phytosanitary measures (namely ISPM 11) to account for environmental risks associated with plant pests (including loss of biodiversity). It reports on support for application of this standard and the adaptation of regional standards for risk assessment to accord with it. Section 4 then looks at a tool for weed risk assessment and its application, and at cooperation between expert organizations to achieve optimum results from pest risk analysis.
International standard for phytosanitary measures ISPM 5: Glossary of phytosanitary terms
Chapter 10 discusses the importance of international standards and pest risk analysis as alternative procedures for justifying imposition of phytosanitary measures. It also covers the use of dispute settlement mechanisms to verify whether countries are implementing phytosanitary measures equitably.
Chapter 11 offers advice to national plant protection organizations on how to embark on a pest risk analysis when environmental risk is involved. It also considers the complexities of analysing the pest risk of secondary pests that indirectly affect plants.
Chapter 12 summarizes the principal tools and resources available for the pest risk assessment component of pest risk analysis and highlights the principal challenges for the future.
Chapter 13 explains how the European and Mediterranean Plant Protection Organization adapted its regional risk assessment and risk management schemes to the revised ISPM 11, also taking into consideration criteria of the Convention on Biological Diversity.
Chapter 14 outlines a weed risk assessment system developed in Australia and capable of adaptation for use elsewhere.
Chapter 15 describes the exceptional ecosystem of the Galapagos Archipelago, the major threat presented by invasive alien species and conservation initiatives. These programmes include an adaptation of the WRA system to assess the potential invasiveness of plant species not yet introduced or determine the priority for eradication efforts of those alien plants already established in the islands. The WRA system is undergoing further modification for use as a pest risk assessment to rank known introduced invertebrates.
Chapter 16 discusses pest risk assessment in Canada and the beneficial effects of a cooperative approach. In particular, for organisms of concern to forestry, a partnership between Canadian Food Inspection Agency (the national plant protection organization) and the Canadian Forest Service has resulted in the completion of challenging pest risk assessments and a good acceptance of resultant decisions.
Options of international standards or pest risk analysis
Pest risk analysis is a key element of all three major international agreements relating to plant protection, namely the International Plant Protection Convention, the World Trade Organizations Agreement on the Application of Sanitary and Phytosanitary Measures and the Convention on Biological Diversity. The IPPC framework, including the national plant protection organizations of all its contracting parties, could well provide an institutional framework that serves the objectives of the CBD and WTO as well.
To combine speed and safety of global movement implies compromise and acceptance of certain risks. Individual countries can manage these risks in a transparent and acceptable way by determining:
Together these three steps constitute the process known as pest risk analysis. Pest risk analysis is a framework for organizing biological and other scientific and economic information to calculate risk (essentially the probability of an unwanted event or hazard occurring multiplied by the magnitude of the consequences if it does happen). This assessment of risk is used to identify appropriate measures to reduce risk to an acceptable level.
To comply with international agreements, countries imposing new phytosanitary regulations must either support them through a pest risk analysis or base them on relevant international standards.
More specific international standards would be useful in harmonizing management options for pest risks. However, the wide variation in pest risks faced by individual countries in relation to introduction and spread of a pest (or pests) associated with a particular commodity usually makes it difficult to develop an agreed international standard. To date, only one specific commodity standard has been accepted under the IPPC as an international standard for phytosanitary measures, namely ISPM 15: Guidelines for regulating wood packaging material in international trade. This standards acceptance was helped in that many countries were in agreement over the risks associated with wood packaging material as a pathway for pests.
If the appropriate phytosanitary standard is not available, countries have the alternative of risk analysis to support restrictive measures.
International harmonization of phytosanitary measures will be successful only if contracting parties implement standards. Control systems are needed to verify whether this is done. The WTO has a dispute settlement mechanism in which the outcome of a dispute settlement is binding on the parties concerned. Phytosanitary disputes may be resolved within the IPPC framework, in a dispute settlement process which relies on the voluntary cooperation of both disputing parties, who are not bound by the findings. The use of the IPPC dispute settlement mechanism could provide valuable jurisprudence for consideration in phytosanitary disputes carried out through the WTO mechanism. To date, no dispute settlement has taken place within the IPPC framework.
Addressing environmental risks associated with plant pests
The contracting parties to the IPPC have developed a reference standard specifically to target the analysis of environmental risks posed by plant pests. This was adopted in April 2003 as a supplement (Analysis of environmental risks) to ISPM 11 : Pest risk analysis for quarantine pests. The standard has been further amended and supplemented to ISPM 11 : Pest risk analysis for quarantine pests, including analysis of environmental risks and living modified organisms. The process of revising ISPM 11  took into account the CBDs guiding principles for the prevention, introduction and mitigation of impacts of invasive alien species. ISPM 11 and other relevant ISPMs provide specific guidance to countries on how to use the information available to make timely decisions about potential threats to plants and plant communities from international trade. The international glossary of phytosanitary terms, ISPM 5, has been supplemented in 2001 with Guidelines on the interpretation and application of the concept of official control for regulated pests and in 2003 with Guidelines on the understanding of potential economic importance and related terms including reference to environmental considerations. These supplements have helped clarify what should be covered by pest risk analysis. Several other recent new or revised standards support pest risk analysis.
Systems for the classification of pests of potential economic significance, generally arthropods and pathogens affecting agriculture or forestry, are well established; identifying species or pathways that pose an environmental risk is a relatively new challenge for NPPOs. Three different approaches for developing an overall PRA strategy to the management of invasive alien species are:
to expand monitoring and regulation to cover taxa and pathways that have not been covered previously
This is particularly pertinent in a country that has not had legislation covering weeds. An NPPO could set up a quick screening process or a partial pest risk analysis on all plant species imported for planting. It would reduce the risk of introducing species of plants that escape their intended use and become countryside weeds or that become more invasive than in their native environment. If a species is found to be suspicious, a full pest risk analysis may be required. Although the focus is on plants for planting, any organism intentionally introduced that will establish a breeding population may warrant a pest risk analysis.
to identify the most important natural systems and/or native plants and review all potential threats to these
NPPOs work with a broad range of stakeholders, including environmental non-governmental organizations, to decide which species or ecosystems that are not already the focus for plant protection effort are the most important to start protecting.
to focus efforts on particular geographic areas or areas with specific levels of protected status.
Limiting an NPPOs efforts to particular geographic areas, such as protected areas or parks, may be a good starting point if resources are limited. Information on such an area will exist, including ecological data; other agencies may have the mandate of protecting the area and add their authority to the outcome of analysis. The constant threat of re-entry of a pest to a protected area from the surrounding area could reduce the cost effectiveness of this approach. However, it could suit countries with natural barriers that will reduce the likelihood of internal spread.
Pests causing indirect injury to plants
An annex to the revision of ISPM 11  states that:
The scope of the IPPC also extends to organisms which are pests because they ... indirectly affect plants through effects on other organisms
In addition to pests that directly affect host plants, there are those, like most weeds/invasive plants, which affect plants primarily by other processes such as competition ...
Such secondary pests are a difficult category for risk analysis. NPPOs could find themselves asked to regulate new pests and pathways for pests that were outside the experience, knowledge and training of their officials. Some of the organisms in this category of pests may be predicted (e.g. parasites of biological control agents or pollinators, species of exotic ants); for others, ecologists may have to sound the warning of the potential threat before an NPPO will know to act.
Resources for pest risk assessments
The principal tools and resources available for the pest risk assessment component of pest risk analysis include:
national data sources
National data will be needed from the PRA area and, to assess entry potential, from the country of origin.
international data sources
Examples include: CAB Internationals Crop Protection Compendium, which can be used to select species that might be present in a commodity based on the pest distribution and host range in the exporting country; climatological information; abstracts of scientific literature; books; pest alerts from regional plant protection organizations; Web search engines.
data sources for assessing entry potential
Data on trade pathways and interceptions (detections in consignments) are most important but usually require specific enquiries for unpublished data.
data sources for assessing establishment potential
If the area of origin and the host plants are known, climates in the area of origin can be compared with climates in the area under threat and the distribution of host plants determined.
data sources for assessing economic, environmental and social impacts
Assembling comprehensive data on a pests impacts in its current range, sufficient biological data to predict its spread and population dynamics in the PRA area coupled with financial, economic, environmental and social data for the enterprises, ecosystems and people likely to be affected may prove difficult. However, assessments can still be made even if data are lacking.
Adaptation of a regional PRA scheme
EPPO supplies a user-friendly questionnaire to assess the risks of organisms that are harmful to plants and to apply pest risk analysis in the framework of the IPPC. This scheme provides technical justification for the regulation of certain pests for the EPPO region (or parts of it) as the PRA area. It has now been adapted to the revised ISPM 11 and will be applicable to pest plants (invasive plants or weeds) and to indirect plant pests (pests that have negative impacts on other organisms resulting in harm to plants).
The structure of the scheme has been altered to accord with the sections of ISPM 11 and a rearrangement of questions to follow it more closely.
The most important changes regarding environmental aspects are the PRA schemes applicability to plants as pests. Invasive plants have effects on the environment; impacts are generally described in qualitative rather than in economic terms. This will be reflected in the revision of the scheme, for example by the following question:
How important is environmental harm caused by the pest within its existing geographic range?
In instances of intentional introduction of a plant, its potential for establishment in an unintended habitat has to be assessed. Intrinsic characteristics of invasiveness should be identified as far as possible, as covered by the following question:
Does the plant have intrinsic attributes that indicate that it could cause significant harm to plants or plant communities?
Weed risk assessment in Australia
Australia applies the principles of pest risk analysis to the review of sanitary and phytosanitary risks associated with the intentional importation of exotic plant species not yet established in the country. The weed risk assessment system was developed to help assess the weed potential of such species. It was calibrated and validated using about 350 exotic plant species that had been present in Australia for sufficient time to reveal their potential as weeds or non-weeds.
Between 1997 and 2003, assessments were carried out for around 1 000 proposals to import plant species into Australia. The WRA score for 30 percent of these was considered too high and the species were prohibited from entry into the country. Close to half of the species (46 percent) were allowed to be imported into Australia. The weed potential of the remainder required further investigation.
Features of the system are:
It is a question-based scoring method.
The assessment can be conducted on a computer using Microsoft® Excel spreadsheets or completed manually using two paper-based forms.
It generates a score for a species based on its history as a weed in other parts of the world, climatic suitability to Australia and biological attributes.
The WRA system is applied only to plant species that satisfy the IPPC definition of a potential quarantine pest.
It does not include risk analysis of pathways.
The system is adaptable and has been modified for use in New Zealand, Hawaii and the Galapagos Islands
The documentation is freely available on the Internet (e.g. at www.ippc.int).
Pest risk analysis in the Galapagos Islands
The Galapagos Archipelago, an exceptional tropical island ecosystem with a high rate of endemism, has attracted considerable national and international effort to conserve its biodiversity. Invasive alien species are a major problem:
More than 17 vertebrate, 550 plant and 500 invertebrate species have been introduced into the Galapagos Archipelago since colonization by human settlers almost 200 years ago.
Alien species are responsible for 11 of the 13 full species extinctions and 39 extinctions of subspecies, races, varieties and populations in the archipelago.
More than 40 of the 550 introduced plant species have become invasive.
Ecuador has approved laws and regulations specifically for conservation of the Galapagos. A special inspection and quarantine system was developed for the archipelago. A list of permitted, restricted and prohibited products for importation into the Galapagos Islands has been developed.
In addition to these environmental protection initiatives, the Australian weed risk assessment system has been adapted and is undergoing further modification to evaluate:
Approaches to pest risk analysis in Canada
In Canada, risk assessment is the responsibility of the Plant Health Risk Assessment Unit of the Canadian Food Inspection Agency. The unit completes 30-50 pest risk assessments a year, including both commodity-based risk assessments and pest-specific risk assessments.
Pest risk assessments have recently been undertaken when:
there is a new pest situation either in Canada or abroad that has implications for Canada
Fanwort, Cabomba caroliniana, an aquatic weed from Asia, is imported for use in aquaria. Its establishment was reported for the first time in Canada in a southern Ontario lake. The pest risk assessment concluded that introduction and establishment elsewhere was very likely. Economic and environmental impacts could be anticipated to include effects on native plant communities, including wild rice, with subsequent effects on water quality, water levels and aquatic animals.
there is a new pest situation abroad that has implications for Canada
there is a new trade situation that presents pest risks not previously addressed
Subsequent to a request to import fresh compost from Cuba, a pest risk assessment identified various plant, animal and human pathogens that could be introduced in the compost and concluded that the product presented an unacceptable risk for Canada.
The diverse nature of the issues involved in risk assessment means that the PHRA Unit may need to seek outside expertise. A cooperative approach, working with other government agencies, academic institutions and industry, has proved effective. In particular, for organisms of concern to forestry, assessments have been successfully completed through a partnership between the CFIA and the Canadian Forest Service.
Phytophthora ramorum, the organism associated with sudden oak death in the United States, has caused significant damage in California. A risk assessment needed not only knowledge of Phytophthora biology and its effects on its hosts but also information about the hosts present in Canada, including their susceptibility to the pest, their prevalence and distribution, and their economic and environmental significance. Other requirements were information on which pathways could be means of spread and what trade occurred for these commodities, together with tools for predicting both distribution and significance of P. ramorum. The P. ramorum risk assessment was the first truly collaborative risk assessment released jointly by the CFIA and CFS. It also drew on the contributions of scientists, biologists and forest managers throughout Canada and internationally. Partnerships of this type contribute significantly to the quality and acceptance of the resulting risk assessment and subsequent quarantine policies, particularly when addressing complex issues where the pest is relatively unknown, and many economic sectors and natural environments may be affected.
The CFS has a mandate to promote sustainable forest management, collect and integrate forestry information, and conduct scientific research in support of forest policy development. A special programme on invasive alien species incorporates six main themes:
In addition to working, with the CFIA, the CFS is increasingly involved with the international community through entities such as the IPPC, the North American Plant Protection Organization, the International Forestry Quarantine Research Group and the International Union of Forest Research Organizations.
For many pest risk analyses, NPPOs will benefit from partnerships with other specialist bodies and experts. Particularly when environmental risk is involved, the information for analysis may include a great many variables, interactions and uncertainty. NPPOs will require the cooperation of ecologists; they will rely on guidance from pragmatic experts who understand the need to make decisions based on the best available information to date, while always highlighting the areas of greatest uncertainty so that new data can quickly be incorporated into historic decisions.
The particular Canadian experience has been that a cooperative approach offers benefits to all partners concerned. Partnerships result in improved pest risk assessment capacity and broadened expertise; these in turn result in a greater credibility on the part of the regulatory body and a greater understanding between partners of the challenges faced by each. This shared responsibility is well viewed by stakeholders, including industry groups, the public at large and non-governmental agencies, and results in a greater acceptance of decisions taken and improved cooperation among stakeholders.
Recommendations on communication and research
Section 4 offers some specific recommendations for improving the quality of pest risk analysis through the dissemination of information and networking. It suggests:
documentation of good pest risk analysis practice in some form of manual to enable others to learn the discipline
development of a workable format for publication of pest risk analyses so that increased numbers of published analyses can demonstrate how they should be constructed.
a mechanism to foster links between PRA practitioners worldwide.
It also recommends additional scientific input into challenging components of pest risk analysis, such as:
This digest consists of information extracted from section 4, together with some background material and explanatory comment. For the full detail, argument, examples and supporting references, please refer to the following chapters 10-16.