Greenhouse gas removal technologies and practices are essential to bring emissions to net zero and limit global warming to 1.5°C. To achieve this, the majority of integrated assessment models (IAMs), that generate future emissions scenarios and inform the international policy process, use large-scale afforestation and biomass energy with carbon capture and storage (BECCS). The feasibility of these technologies and practices have only so far been considered from a relatively narrow techno-economic or biophysical perspective. Here, we present one of the first studies to elicit perspectives through an expert mapping process to open up and broaden the discussion around feasibility of afforestation and BECCS. Our stakeholders included business and industry, non-governmental organisations and policy makers, spanning expertise in bioenergy, forestry, CCS and climate change. Perspectives were elicited on 1) issues relating to BECCS with large-scale afforestation, and 2) specific criteria for assessing feasibility. Participants identified 12 main themes with 61 sub-themes around issues, and 11 main themes with 33 sub-themes around feasibility criteria. Our findings show important societal and governance aspects of feasibility that are currently under-represented, specifically issues around real-world complexity, competing human needs, justice and ethics. Unique to the use of these technologies for greenhouse gas removal are issues around temporal and spatial scale, and greenhouse gas accounting. Using these expert insights, we highlight where IAMs currently poorly capture these concerns. These broader, often more qualitative perspectives, issues and uncertainties must be recognised and accounted for, in order to understand the real-world feasibility of large-scale afforestation and BECCS and the role they play in limiting climate change. These considerations enable widening the scope to broader and deeper discussions about possible and desirable futures, beyond a focus on achieving net-zero emissions, attentive to the effects such decisions may have. We outline approaches that can be used to attend to the complex social and political dimensions that IAMs do not render. By complementing IAMs in this way opportunities can be created to open up considerations of future options and alternatives beyond those framings proposed by IAMs, creating opportunities for inclusion of knowledges, reflexivity and responsibility.