Due to growing global energy demand and consumption, emission reduction alone will be insufficient for reaching the 1.5-degree objective. Additional greenhouse gas removal measures - either through technological innovation or natural carbon sinks - are increasingly popular forms of climate action. Amongst those, forests as socio-technical ecologies take a prominent position due to their natural ability to bind carbon in their biomass. As the marketization of carbon sequestration has been criticized for causing more emissions than avoiding them, my project proposal suggests looking at other speculative practices with trees. Connecting anthropological literature on speculation to Science and Technology studies research on alternative ways in which humans and the environment engage with each other, my project is guided by the question of how forests participate in transforming the relationship between nature and culture, and asks: What are the social and political implications for constructing the future through trees? Applying a multi-sited ethnographic approach, I will study how boundaries between nature and culture are renegotiated through biomass-based greenhouse gas removal techniques, and contribute with this project to the social study of climate change.