John Wiley & Sons, Ltd.

A risk assessment example for soil invertebrates using spatially explicit agent‐based models (ABMs)


Current risk assessment methods for measuring the toxicity of plant protection products (PPPs) on soil invertebrates use standardised laboratory conditions to determine acute effects on mortality and sublethal effects on reproduction. If an unacceptable risk is identified at the lower tier, population‐level effects are assessed using semi‐field and field trials at a higher tier because modeling methods for extrapolating available lower tier information to population effects have not yet been implemented. Field trials are expensive, time‐consuming and cannot be applied to variable landscape scenarios. Mechanistic modelling of the toxicological effects of PPPs on individuals and their responses combined with simulation of population‐level response shows great potential in fulfilling such a need, aiding ecologically informed extrapolation. Here, we introduce and demonstrate the potential of two population models for ubiquitous soil invertebrates (collembolans and earthworms) as refinement options in current risk assessment. Both are spatially explicit agent‐based models (ABMs), incorporating individual and landscape variability. The models were used to provide refined risk assessments for different application scenarios of a hypothetical pesticide applied to potato crops (full‐field spray onto the soil surface [termed “overall”], in‐furrow, and soil‐incorporated pesticide applications). In the refined risk assessment, the population models suggest that soil invertebrate populations would likely recover within 1 year following pesticide application regardless of application method. The population modeling for both soil organisms also illustrated that a lower predicted average environmental concentration in soil (PECsoil) could potentially lead to greater effects at the population level depending on the spatial heterogeneity of the pesticide and the behaviour of the soil organisms. Population‐level effects of spatial‐temporal variations in exposure were elucidated in the refined risk assessment using ABMs and population‐level endpoints while yielding outputs that directly address the protection goals. We recommend choosing model outputs that are closely related to specific protection goals, using available toxicity data and accepted fate models to the extent possible in parameterising models to minimise additional data needs, and testing, evaluating and documenting models following recent guidance. This article is protected by copyright. All rights reserved

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