Microbes are mediators of ecosystem processes and play a major role in determining their fate under global climate change. As climate changes, microbial influences on ecosystem processes will vary depending on both community and evolutionary dynamics. However, assessing and modeling the adaptive response of microbes to changing environments remains a major challenge because basic microbial eco-evolutionary questions have been overlooked, and thus, remain unanswered. For example, how are microbial ecological and evolutionary processes interconnected? How do each and their interactions change in response to climate change? How do their responses translate to ecosystem-scale impacts? Discussing these questions will allow us to better assess the consequences of microbial responses to ecosystem-scale processes under global climate change. The purpose of this session is to share insights to spark new ideas for connecting concepts from ecology and evolution to find what matters in microbial responses to global climate change. We will discuss new ideas related to microbial traits and ecosystem processes under the lens of evolutionary biology. We discuss perks of connecting ecology and evolution from a microbial and ecosystem-scale perspective. We explore how genes connect to traits in microbes and how these traits connect to ecosystem-scale processes in the context of climate change and evolutionary adaptation. Finally, we focus on how modelling can help us connect both perspectives to better predict the future of microbially-mediated biogeochemical processes.