Cumulative effects assessment (CEA), as a required practice for the environmental assessment (EA) of projects in many countries, faces several practical challenges, especially related to biodiversity. Drawing on the perspectives and experiences of Canadian EA practitioners, this paper explores options or drivers of change for improving project-based assessment to better tackle cumulative effects on biodiversity. An on-line survey was conducted with 40 professionals from the private sector, government departments/agencies, universities, and non-governmental organizations, examining the current challenges and opportunities regarding: CEA process for biodiversity; responsibilities for undertaking CEA tasks; resources to support and promote good CEA practice. In terms of process, there is shared understanding on: (i) the need of EA terms of reference to provide specific directions on CEA; (ii) CEA should capture both human and natural drivers of cumulative change; (iii) spatial boundaries for CEA should be based on ecological boundaries. There are dissenting views about: (i) whether CEA should consider all valued components (VCs) potentially affected by a project or only those for which residual effects are predicted; and (ii) delimitation of future temporal limits. In terms of responsibilities, participants agreed that project proponents should retain a central role in conducting CEA, but government agencies should lead the collection/provision of information about other projects in the study area and baseline VC conditions. Information and knowledge management resources could be also applied in the context of governmental agencies and consultancy firms to support CEA for biodiversity.