Star formation and its subsequent feedback are fundamental processes shaping the ecology of galaxies. However, the details on how they affect the local properties of the interstellar medium (ISM) as well as shape galactic-scale star formation histories are currently actively debated. In my talk I will use the high resolution (20 pc) VINTERGATAN cosmological zoom-in simulation to study the evolution of the ISM and its star formation efficiency per free-fall time on giant molecular cloud (GMC) scales across cosmic time. The simulated Milky Way-like galaxy experiences periods of starburst activity and short global gas depletion times (1 < z < 5) when the cold ISM reaches its densest and most turbulent states. More quiescent star formation during a secularly evolving phase (z < 1) shows a less dense and turbulent cold ISM with order of magnitude longer global gas depletion times of a few Gyr. Despite clear significant changes in the global star formation timescales as well as the density and velocity dispersion distributions computed on GMC scales over time, the mass-weighted average star formation efficiency per free-fall time remains at a constant ~1%. The stability of this local efficiency arises from a tight coupling between the kinetic-to-gravitational energy ratio in star-forming regions across cosmic time and is consistent with observations of star-forming GMCs (cf. PHANGS collaboration). These findings have strong implications when studying the tight connection between star formation and stellar feedback and their future modeling as a function of redshift. In fact, my results have helped relief recently reported tensions when exploring the dependency of the local efficiency with respect to the virial parameter in GMCs, where turbulence-regulated star formation efficiency models are in apparent contradiction with observed efficiency estimators.
