ERAHUMED: An integrated modelling platform for the landscape-level ecological risk assessment of pesticides used in rice-farming systems

Abstract

Pesticides are major stressors affecting freshwater biodiversity; however, the cumulative risks posed by multiple substances used within the same crop, across different crops, or over multi-year application cycles remain poorly understood. Here we introduce the ERAHUMED model, a modeling platform designed to assess the ecological risks of pesticide mixtures associated with rice farming at the landscape scale. The model uses the Albufera Natural Park (Valencia, Spain), one of the most important Mediterranean coastal wetlands, as a reference area. ERAHUMED integrates a hydrological module, an agricultural management module, a three-compartment (plant, water, sediment) pesticide exposure module, and a risk assessment module that employs both deterministic and probabilistic approaches for calculating pesticide risks. The model's novelty lies in its capacity to evaluate how different agrochemical management practices, including various pesticide application schemes and spatial crop patterns, along with landscape architecture, climate, and hydrological variations, influence pesticide exposure and associated risks to aquatic ecosystems. Here, we detail the model’s core principles, its calibration and validation using monitoring data, and present two application case studies. These case studies demonstrate how the model can be used to compare the ecological risks posed by old and current pesticide application schemes at the landscape scale, as well as to assess the influence of extreme climatic events on pesticide exposure and risks in downstream water bodies. The model is implemented as an R package with an integrated Shiny-based graphical user interface. This implementation enables efficient landscape-scale evaluations of pesticide application schemes, agricultural management practices, and their associated ecological risks for a broad range of users, with a particular focus on researchers and environmental managers aimed at minimizing pesticide risks.