The ability of forests to sequester carbon has made afforestation a critical tool in climate change mitigation. Deployed under the broad umbrella of nature-based climate solutions or forest carbon offset programs, afforestation efforts are underway across the globe, with the tropics serving as critical venues for these efforts. Forests, however, are themselves vulnerable to the direct and indirect impacts of climate change such as increased temperatures, more frequent fires, and disease outbreaks. As efforts to limit greenhouse gas emissions stutter, the longevity of these afforestation efforts and their intended benefits remains underexplored. We investigated this issue in the context of ongoing afforestation efforts in Kenya. These afforestation efforts are underway to meet a constitutionally mandated national forest cover of 10%. Using L-Range, a model that simulates plant growth and the flow of carbon within rangeland ecosystems, we explored how existing and potential Kenyan forests will respond under different scenarios of climate change. We performed simulation experiments with L-Range using remotely sensed information for forest, land cover, and soil composition. Climate change impacts were explored using CMIP6 climate projections for three future emission-mitigation scenarios (SSP 1-RCP 2.6, SSP 2 – RCP 4.5, and SSP 3 – RCP 7.0). We also explored the additive impacts of increased fire frequency on forest cover. For each of these scenarios we calculated the change in forest cover and carbon sequestered within forests in the years 2050 and 2100 relative to a baseline year of 2010. We found that in Kenya, evergreen forests in particular experience spatially variable losses in extent under all scenarios (up to -5%). These losses in extent were accompanied by a decline in the amount of carbon sequestered within soils. We interpret these forest cover changes within the social context of each SSP-RCP scenario and ongoing afforestation efforts. Our findings suggest that the climate change mitigation potential from afforestation may be characterized by diminishing returns in the absence of concerted global efforts to rein in carbon emissions, and that real-time monitoring via ground and remotely sensed platforms will play a critical role in planning for an uncertain future.