Species losses have always occurred as a natural phenomenon, but the pace at which species are going extinct has recently accelerated dramatically as a result of human activities. The disappearance of a species can have far-reaching and often unexpected consequences for other species, since changes can propagate throughout ecosystems. Hence, the following questions arise: 

- How does the collapse of one ecosystem compartment (species or functional groups) influence the remaining ecosystem compartments? 

- How is an ecosystem.s structure related to its vulnerability to compartment collapses?