What information might the geographer be able to convey more clearly than the economic historian

Since a geographer is the scientist whose field of study is geography, the study of Earth's natural environment as well as human society, an information that a geographer might be able to convey more clearly than the economic historian would be the patterns of how human beings migrated over time as a result of the climate change and environment which made them to move. 

On the other hand, economic historians are responsible with the study of economies or economic phenomena of the past.

seeing as no choices were provided, i'll do my best to answer it from knowledge.

job specialization promotes work ethic to the person doing the job. he/she may be strong in the arms and able to lift things, specializing him/her in a job where you lift and carry.