Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides,

Metapopulation Model for Assessing Spatial and Temporal Effects of Pesticides... 

In this chapter we present an individual-based population model (Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides [MASTEP]). M ASTEP describes the effects on, and recovery of, populations of the water louse Asellus aqua-ticus following exposure to a fast-acting, nonpersistent insecticide caused by spray drift for pond, ditch, and stream scenarios. The model used the spatial and temporal distribution of the exposure in different treatment conditions as an input parameter. A dose-response relation derived from a hypothetical mesocosm study was used to link the exposure with the effects. The modeled landscape was represented as a lattice of 1 x 1 m cells. The model included processes of mortality of A. aquaticus, life history, random walk between cells, density-dependent population regulation, and in the case of the stream scenario, medium-distance drift of A. aquaticus due to flow. All parameter estimates were based on the results of a thorough review of published information on the ecology of A. aquaticus and expert judgment. 

FIGURE 6.1 Overview of the scheduling of state change for an Asellus individual in the Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides (M ASTEP). In boxes the different events in its life history are shown, and in italics the origin of the time delay after which the event takes place. Arrows without text point to events that take place immediately (time delay of 0). The main loops are the ones occurring with a 1-day time delay checking for density-dependent mortality, and the movement loop. Pesticide application was scheduled as a separate event. 

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