Carrying capacity and cumulative effects management: A case study using bighorn sheep

Abstract

Successful cumulative effects management is fundamental for conservation policy and practice. We investigated the application of a carrying capacity (CC) model as a cumulative effects management tool for bighorn sheep (Ovis canadensis canadensis) in British Columbia, Canada, where CC is defined as the natural limit of a sustainable population that is set by the availability of resources in the environment. We estimated winter CC using forage availability across winter ranges, weighted by relative selection by sheep and a safe use factor, and divided by overwinter forage requirements to determine how many sheep the landscape can support. We explored application of our model to decision-making about new industrial projects or conservation activities in a cumulative effects context. Cumulative effects include both positive and negative contributions to animal populations and we simulated the potential positive outcomes of burning to increase bighorn sheep carrying capacity in our study area. Our results show that carefully planned conservation actions could generate a 5% increase in CC (i.e., from 493 to 519 sheep). Robust tools and scientific techniques that are capable of quantifying multiple impacts and conservation actions and that consider spatial processes over long temporal scales, such as the CC model presented, should be applied to help inform decisions about how to better manage cumulative habitat change and achieve conservation objectives.