Abstract: Towers species can significantly affect the properties of gravitational effective field theories. They naturally appear in string theory, and one of their universal effects is a renormalization of the scale at which gravity becomes strongly coupled. In this talk, we will discuss some of the implications for cosmology arising from the presence of a large number of species. A major focus will be on cosmic inflation and its observational signatures in the cosmic microwave background. We will also discuss some of the implications for Starobinsky inflation.