Final answer:
Ecosystem disruptions lead to population shifts due to changes in the environment, with examples including the decline in biodiversity from damming rivers and the collapse of fisheries from overfishing.
Step-by-step explanation:
Disruptions to any physical or biological component of an ecosystem, whether natural or human-made, can lead to shifts in populations by altering the environment and the availability of resources. An example would be the effect of damming on river ecosystems, which can significantly alter water flow and lead to reductions or eliminations of species adapted to natural river conditions. This can cause significant declines in biodiversity, exemplified by the Western Atlantic cod fishery collapse due to overfishing. Conservationists are concerned about both types of disturbances because they affect entire ecosystems, often leading to long-term negative impacts on species populations and the environment.