The Giraffe population increased because there were more trees available which means there was more leaves for the Giraffes and gave birth to more Giraffes and they had more leaves to eat until they reached their maximum carrying capacity and had a steady flow of resources.
These are the leaves that Giraffes eat and they come from Mimosa and Acacia trees.
Some Giraffes have small necks or small legs and can cause them to die quickly because they cant reach the leaves to get food and can only get food scarcely.
Immigration could influence the population of Giraffes by bringing them to areas that have more Mimosa and Acacia trees and providing more resources for the population, which would help the Giraffe population rise to its carrying capacity.
Emigration relates to Immigration the Giraffes could move out of the area and emigrate to another and possibly find better areas but could also bring them to areas that have bad influences and not enough resources.
Births could influence the population in a good way if the babies are raised healthy and then they could give birth to more and bring the population up but if there are to many births then they could overpopulate and there wouldn't be enough food.
Deaths of the population could be ok if there are too many Giraffes and not enough food but if there are too many deaths then the population could go extinct if there are not enough births.
Limited resources could cause the population to go along the S-curve by not having enough food so they die but then the population slowly rises back up as there are more births and food available. Then the population reaches its max carrying capacity in which the maximum number of individuals of a certain species an environment can support.
Two density-dependent factors would be competition for example only a certain amount of food or Giraffes with short legs or necks so they get less food and have to try harder to get food.
Two density-independent factors would be from construction or natural disasters and sudden environment changes like pollution for example.