The paradigm of effective field theory lies at the heart of modern high-energy theoretical physics. However, in the context of quantum gravity, non-trivial relations between low-energy (IR) and high-energy (UV) quantities may arise. In the spirit of understanding such relations and their phenomenological consequences on general grounds, I will present a recent analysis of dark energy in weakly coupled string theory. The upshot is a simple general relation between dark energy and the scales of new physics, whose phenomenological consequences I will discuss.