Inbreeding depression is a serious concern in small populations of endangered organisms. Why is inbreeding depression a concern for such populations?

Inbreeding results in small genetic diversity in the offsprings as parents are mating within the same 'family tree', which is often the case for endangered organisms. With little genetic diversity, there is no variation for natural selection to act on and hence the species is vulnerable to changes in their environment. Any change in the environment has the potential to wipe out the entire population as there is no genetic diversity that allows a selected few to withstand the environmental change. For example, if there were to be a temperature change in the habitat, the endangered species could go extinct.