Guidance for analytical methods to cumulative effects assessment for terrestrial species

Abstract

Landscapes in Canada are undergoing change due to resource and land use stressors and climate stressors. Understanding the cumulative effects of these stressors is challenging because of the complexity of ecosystems, the variability of stressors, and species response to individual or multiple stressors. A key challenge within the field of cumulative effects assessment (CEA) is guidance that describes and evaluates analytical methods. In this review we discuss four broad categories of methods with current or potential use for project-based and effects-based CEA for species in terrestrial systems: (i) qualitative review, (ii) habitat supply models, (iii) empirical species–stressor models, and (iv) decision support models. We describe each method and provide examples, highlight advantages and limitations, identify how methods address key science-based CEA questions, and provide direction on when and why to use specific CEA methods. Empirical species–stressor models and decision support models are the only analytical approaches that provide answers to many science-based CEA questions including how multiple stressors combine to affect an individual species and the certainty of multiple stressor effects. We provide recommendations for using one or more methods as complementary building blocks to fill data gaps, improve understanding and communication, engage diverse partner groups, and increase the quality and credibility of the CEA. Our review supports a move toward regional scale, effects-based CEA where partner collaboration to design, implement, and analyze comprehensive assessments of multiple stressors will (i) expand our knowledge of terrestrial species response to stressors and (ii) inform best management practices for resource industries and conservation and management actions for land managers.