Pest risk analysis and the international plant protection convention
Introduced plant pests can lower crop yields and have environmental impacts. The spread of plant pests from one geographical area to another is an issue of international concern. The principal international agreement aimed at addressing the spread of plant pests through international trade is the International Plant Protection Convention, a multilateral treaty for international cooperation in plant protection aimed at preventing the spread of pests of plants and plant products, and promoting appropriate measures for their control (IPPC, Article I.1). In accordance with the WTO Sanitary and Phytosanitary Agreement the IPPC aims to protect plants while limiting interference with international trade.Liebhold, A. M., Brockerhoff, E.G., Garrett, L.J., Parke, J. L. & Britton, K. O. (2012) Live plant imports: the major pathway for forest insect and pathogen invasions of the US. Frontiers in Ecology and the Environment 10, 135–143. A key principle of the IPPC is that contracting parties (signatories) provide ‘technical justification’ to support phytosanitary decision making affecting trade. The IPPC recognises pest risk analysis as the appropriate format for such technical justification. The responsibility for conducting pest risk analysis sits within government, specifically within a country's National Plant Protection Organization (NPPO) and comes as an obligation when countries become contracting parties to the IPPC (IPPC Article IV, 2a). IPPC standards, referred to as International Standards for Phytosanitary Measures (ISPM), have been developed to assist NPPOs. The primary ISPMs relevant to pest risk analysis are ISPM 2, Framework for pest risk analysis, ISPM 11, Pest risk analysis for quarantine pestsFAO (2013) ISPM No. 11 Pest risk analysis for quarantine pests, FAO Rome, 26 pp. and ISPM 21, Pest risk analysis for regulated non-quarantine pests. Although ISPMs relating to pest risk analysis provide guidance regarding the factors to consider when conducting analyses, they do not provide instructions as to how to actually perform a pest risk analysis. However, many countries including Australia, New Zealand and the USA, have developed procedures to assess the pest risks associated with the import of plant commodities. Devorshak (2012) describes the principles of pest risk analysis, how analyses can be performed and the use of pest risk analysis in regulatory plant protection. A general guide to the principles of pest risk analysis for plant pests and a description of some of the problems and difficulties that may be encountered when undertaking such analyses are included in text by Ebbels (2003) which also covers wider plant health issues.Stages within a pest risk analysis
In accordance with ISPM 11, a pest risk analysis consists of three stages.Stage 1: initiation
Common reasons for initiating a pest risk analysis include: * Pest-based information, e.g. a pest is detected during inspection of an imported commodity; a pest is reported to be spreading; a pest outbreak is detected; a new pest is reported in scientific literature. * Pathway-based information, e.g. a mechanism potentially facilitating the entry or spread of a pest is identified. Mechanisms include new trade pathways, usually of plants or plant products but could also include articles used in the transport and distribution of traded goods such as pests carried as contaminants of passenger baggage and natural spread. * Review of existing phytosanitary policy, e.g. new information that impacts on an earlier phytosanitary decision can cause a review of policy as can disputes over phytosanitary measures. Within the initiation stage of a pest risk analysis the reason for conducting the analysis, the identity of the pest and or pathways being analysed and the area in relation to which the analysis is conducted (the pest risk analysis area) is provided.Stage 2: pest risk assessment
There are three steps to the assessment of pest risk. *Step 1: Pest categorization The purpose of pest categorization is to determine whether a pest identified during the initiation stage satisfies the criteria of being a quarantine pest. A quarantine pest is a pest of potential economic importance to the area endangered thereby and not yet present there, or present but not widely distributed and being officially controlled. Pest categorization includes all the main elements considered in Step 2 of a pest risk assessment but the elements are considered in less detail and pest categorization is essentially a quick assessment of whether the analysis should continue. The categorization step provides an opportunity to eliminate a pest from analysis at an early stage in the pest risk analysis process thus avoiding unnecessary in-depth examination. Pest categorization can be done with relatively little information, provided that the information available is sufficient to carry out the categorization. *Step 2: Assessment of pest entry, establishment and spread. Assessing the likelihood of pest entry requires assessment of each of the pathways with which a pest may be associated, from its origin to its establishment in the pest risk analysis area. In a pest risk analysis initiated by a specific pathway, often an imported commodity or goods associated with an imported commodity, e.g. packing materials, the probability of pest entry is evaluated for that specific pathway. For a pest risk analysis initiated for a specific pest, all probable pathways are evaluated for that individual pest. To estimate the likelihood of establishment of a pest, biological information about the pest including its life cycle, itsStage 3: pest risk management
For a quarantine pest, pest risk management is the process of evaluation and selection of options to reduce the risk of introduction and spread of the pest. Conclusions from the pest risk assessment (Stage 2) are used to support decisions regarding the level of risk presented by the pest. If a pest is judged to present an unacceptable risk then phytosanitary measures should be identified that will reduce the risk to an acceptable level. Phytosanitary measures should accord with IPPC principles of necessity, managed risk, minimal impact, transparency, harmonization, non-discrimination and technical justification. ISPM 11 provides more information about each stage of pest risk analysis for quarantine pests.Level of detail required
The level of detail in a pest risk analysis will be limited by the amount and quality of information available, the tools, and time available before a decision is required. Quantitative and qualitative techniques are used in pest risk analysis but pest risk analysis need only be as complex as is required by the circumstances to support a phytosanitary decision and provide the necessary technical justification to defend decisions regarding phytosanitary measures. Nevertheless, a pest risk analysis should be based on sound science, be transparent and consistent with other pest risk analyses conducted by the NPPO. Examples of pest risk analysis are available in the EPPO Platform on PRA.Uncertainty
Estimating the likelihood of pest introduction and of the consequences that could result involves many uncertainties. Uncertainty is always part of pest risk analysis; very often there is a lack of data necessary to reach secure conclusions. The subjective nature of pest risk analysis is also a source of uncertainty. ISPM 11 recognises that pest risk analysis involves many uncertainties, largely since estimates and extrapolations are made from real situations where the pest occurs to a hypothetical situation in the pest risk analysis area. In most cases analyses performed during pest risk analysis use historical data to forecast potential future events. It is important to document the areas of uncertainty and the degree of uncertainty in the assessment, and to indicate where expert judgement has been used. This is necessary for transparency and may also be useful for identifying and prioritizing research needs.Criticism of pest risk analysis
Pest risk analysis, as conducted under the IPPC and SPS Agreement, has been criticised for being reactive, only coming into effect after a pest problem has been identified. For example, many pests now subject to phytosanitary measures, supported by pest risk analysis, only became recognised as potential risks once they had already escaped from their geographical centres of origin and caused impacts in other parts of the world. Some ‘newly escaped’ organisms were previously unknown to science before they escaped and current international standards for pest risk analysis cannot assess risks from unknown organisms. In addition, a pest risk analysis will focus on a pest at the species level assuming the pest to be genetically stable but this can be a great oversimplification if the pest has a short generation time with capacity for rapid genetic change. During the assessment of impact, assessors focus on impacts on known hosts or habitats. However, if a pest adapts to a new host plantGilbert GS & Webb CO (2007) Phylogenetic signal in plant pathogen-host range. Proceedings of the National Academy of Sciences USA 104, 4979–4983. or habitat once established in the pest risk analysis area, impacts will be underestimated. Risk analyses forSee also
* Convention on Biological Diversity *Further reading
* Ebbels, D.L. & King, J.E. (Eds). Plant Health: The Scientific Basis for Administrative Control of Plant Diseases and Pests. Blackwell Scientific Publishing, Oxford. 1979. 322pp. * Gordh, G. & McKirdy, S. (Eds). The Handbook of Plant Biosecurity: Principles and Practices for the Identification, Containment and Control of Organisms that Threaten Agriculture and the Environment Globally. Springer, Netherlands. 2014. 723pp. * Jarrad, F., Low-Choy, S. & Mengersen, K. (Eds). Biosecurity Surveillance Quantitative Approaches. CABI, Wallingford. 2015. 374pp. * MacLeod, A., Pautasso, M., Jeger, M.J., Haines-Young, R. (2010) Evolution of the international regulation of plant pests and challenges for future plant health, Food Security, 2 (1) 49–70.References
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