Research Document - 2007/051

A quantitative approach to assessing allowable harm in species at risk: application to the Laurentian black redhorse (Moxostoma duquesnei)

By Vélez-Espino, L.A. and M.A. Koops

Abstract

The Species at Risk Act (SARA), intended to protect species at risk of extinction or extirpation in Canada and to promote their recovery, determines population resilience to human-induced harm by conducting what has been termed an allowable harm analysis (AHA), but which is now part of the recovery potential assessment (RPA). The function of an AHA is to provide scientific advice about the level of harm a species (or population) can withstand without compromising recovery or survival. Here we develop a methodology to quantitatively estimate allowable harm within a demographic framework. After defining harm as a negative perturbation that can target one or more vital rates and life stages simultaneously, allowable harm is calculated as a function of (a) the vital rate(s) impacted by human action(s), (b) the elasticities of impacted vital rate(s), (c) the population growth rate prevailing before the harm occurs, and (d) the minimum population growth rate that will not jeopardize the survival and future recovery of the population. Additional characteristics of our approach are that it requires minimal data while using all available data, can link population dynamics with habitat supply, is flexible enough to encompass complex life histories, and it follows a precautionary approach. We demonstrate this methodology by applying it to a Canadian population of the threatened black redhorse (Moxostoma duquesnei).

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