Abstract
Pest Risk Assessments (PRAs) routinely employ climatic niche models to identify endangered areas. Typically, these models consider only climatic factors, ignoring the ‘Swiss Cheese’ nature of species ranges due to the interplay of climatic and habitat factors. As part of a PRA conducted for the European and Mediterranean Plant Protection Organization, we developed a climatic niche model for Parthenium hysterophorus, explicitly including the effects of irrigation where it was known to be practiced. We then downscaled the climatic risk model using two different methods to identify the suitable habitat types: expert opinion (following the EPPO PRA guidelines) and inferred from the global spatial distribution. The PRA revealed a substantial risk to the EPPO region and Central and Western Africa, highlighting the desirability of avoiding an invasion by P. hysterophorus. We also consider the effects of climate change on the modelled risks. The climate change scenario indicated the risk of substantial further spread of P. hysterophorus in temperate northern hemisphere regions (North America, Europe and the northern Middle East), and also high elevation equatorial regions (Western Brazil, Central Africa, and South East Asia) if minimum temperatures increase substantially. Downscaling the climate model using habitat factors resulted in substantial (approximately 22–53%) reductions in the areas estimated to be endangered. Applying expert assessments as to suitable habitat classes resulted in the greatest reduction in the estimated endangered area, whereas inferring suitable habitats factors from distribution data identified more land use classes and a larger endangered area. Despite some scaling issues with using a globally conformal Land Use Systems dataset, the inferential downscaling method shows promise as a routine addition to the PRA toolkit, as either a direct model component, or simply as a means of better informing an expert assessment of the suitable habitat types.
Highlights
Whilst the roots of pest risk modelling extend back to early in the 20th Century [1], modern computer-based pest risk modelling has only been practised for some 30 years [2,3]
Under the International Standards for Phytosanitary Measures (ISPM’s), Pest Risk Assessments (PRAs) need to identify the endangered area, “an area where ecological factors favour the establishment of a pest whose presence in the area will result in economically important loss” [13]
If human disturbance patterns are extended into this region, we may find that P. hysterophorus extends its range there
Summary
Whilst the roots of pest risk modelling extend back to early in the 20th Century [1], modern computer-based pest risk modelling has only been practised for some 30 years [2,3]. A thirst for more detailed risk maps saw the development of finer-scaled gridded climate datasets [7,8,9], and their application to pest risk modelling problems e.g., [10,11,12]. Under the International Standards for Phytosanitary Measures (ISPM’s), Pest Risk Assessments (PRAs) need to identify the endangered area, “an area where ecological factors favour the establishment of a pest whose presence in the area will result in economically important loss” [13]. . .an officially defined country, part of a country, or all or part of several countries”, the Decision-support scheme for quarantine pests of the European and Mediterranean Plant Protection Organisation [14] encourages the risk assessor to define the endangered area at a very fine ecological and geographical scale. Ecological theory indicates that we need to consider the effects of non-climatic factors as we investigate species niches at finer geographical scales [15]
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