How might a measure of population density be more useful than a simple population estimate? If I told u that there were 50 oak trees is that a large number or a small number of oak trees?
Answer: Population density describe the spread of living organisms on the certain territory, while the number of population is irrelevant to the area. 50 oak trees can be a lot for 100 m^ 2 , but very small amount for 1000 m^ 2 . That is why, population density indicator is more informative.