  In this Note, we describe the stationary equilibria and the asymptotic
behaviour of an heterogeneous logistic reaction-diffusion equation under the
influence of autonomous or time-periodic forcing terms. We show that the study
of the asymptotic behaviour in the time-periodic forcing case can be reduced to
the autonomous one, the last one being described in function of the "size" of
the external perturbation. Our results can be interpreted in terms of maximal
sustainable yields from populations. We briefly discuss this last aspect
through a numerical computation.
