Peter Abrams has suggested that our Trends paper does not review enough literature and therefore is premature in dismissing mechanisms he has suggested are likely to give rise to positive population responses to mortality in nature. We disagree that it is premature but we agree more empirical work is required, particularly with model organisms that are more likely to be represented by his models so his predictions can be tested. We welcome this discussion.
Despite being pointed out in various experiments since the very beginning of the science of ecology, there is little current appreciation for the role of density dependence in producing positive population responses to mortality. In such cases, population abundance responds initially positively to increasing mortality until a point when the mortality first reduces this positive effect, then eventually leads to population decline. A number of authors have begun to explore this phenomenon in recent years and have proposed different views as to how they can come about. Here we reviewed those proposed mechanisms and crucially looked to experimental evidence in the laboratory and in the wild that helped us to differentiate between which mechanism is more likely to occur in nature.