Most emission scenarios that aim to restrict warming to below 2°C require substantial land-based mitigation via carbon uptake by bioenergy expansion or re/afforestation. Here, we use the Community Earth System Model to assess the carbon and climate implications of two land-based mitigation scenarios designed to achieve the same radiative forcing, one primarily driven by bioenergy expansion and the other by re/afforestation. We find a net land carbon sink (248~519 PgC) in the re/afforestation scenario by 2100. The bioenergy expansion-focused scenario has a much larger spread in the effective land carbon sink (-62~726 PgC by 2100), due to uncertainties in biomass yield, trends in energy conversion technology, and carbon capture and storage efficiency. Although bioenergy expansion results in a relatively coolerclimate in many regions compared to the re/afforestation scenario, it reshuffles the geography of regional warming hotspots, amplifying the risk of heat extremes for the most vulnerable tropics (e.g., Central Africa, Southeast Asia). These simulation results indicate that a thorough accounting of bioenergy-related land-use emissions and land-atmosphere interactions is required to assess the relative effectiveness of bioenergy expansion versus re/afforestation. Future land use planning needs to optimally locate suitable re/afforestation and bioenergy expansion regions to maximize the likelihood of success of the intended climate mitigation outcomes.