Asociologist is studying how the population of certain countries influences and affects the population and environment of other neighboring countries. this sociologist is most likely a:

A sociologist who is studying how populations of certain countries influences and affects the population and environment of other neighboring countries is likely a functionalist, who focuses on social/cultural development, international social change and or culture sociology. The focus area described allows for may courses of sub-study. The dynamic of entire populations especially those separated by boarders and boundaries can have vastly different cultural norms, the result of which when mixed can have a catastrophic difference on the perceived efficiency of that population as a whole. One example of this explanation is cultural social conflict, evident in most if not all large cities with discontinuous ethnic groups.

Reserved powers is your answer