Biodiversity is implicitly or explicitly included as a protection goal in many risk assessment directives and regulations. Recently, a model was published that predicts chemical-induced biodiversity changes based on (1) the tolerance variability among and within species; and (2) dispersal limitation, i.e. the degree of isolation of a local community from the surrounding species pool. Here, I calculate the 'local species extinction risk' for a focal algal community, at a control and at 4 concentrations of a hypothetical herbicide, corresponding to the <1st, 50th, 100th and >100thpercentile of the uniform species sensitivity distribution of this community (ssd, min=50, max=100). This extinction risk is the probability that a species present in the surrounding species pool would not appear in the focal community. Control extinction risk was, on average, 75% and the increase of this risk with herbicide exposure was smallest when the tolerance variability among species was ten times lower than within species and highest otherwise, demonstrating the buffering capacity of intraspecific variability against herbicide-induced extinctions. Despite the fact that mean tolerances of all species were exceeded at the 100th and >100thpercentiles, community extinction was extremely rare. Thus, risk assessments based on species tolerance only will overestimate chemical-induced diversity loss at elevated concentrations.

Biodiversity models for the risk assessment of pesticides

248th National Meeting (2014)

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