The population increases when:
Net reproductive rate R0 is the expected number of daughters produced by a female over her lifetime, adjusted for survival to each reproductive age. If R0 exceeds 1, each generation more than replaces itself, so abundance increases from generation to generation under stable conditions. R0 = 1 denotes exact replacement, and R0 below 1 indicates generational decline. This discrete-generation criterion parallels λ > 1 for finite growth and r > 0 for continuous growth, although the quantities are not numerically interchangeable without information about generation time and age structure. A negativ
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 11