Immigration: Immigration is the movement of individuals or a group to a new community or region. Green sea turtles migrate for multiple reasons; like looking for more resources or mating opportunities. Immigration causes an increase in population so when sea turtles immigrate they are adding on to existing populations.
Emigration: Emigration is the movement of individuals out of a native area. When green sea turtles emigrate it might be because they're current population is dying off, not finding enough resources, or individuals cannot find others to mate with. When the turtle, or turtles leave, it causes a decrease in their population.
Birth: As the sea turtle population produces offspring it creates an increase in their population and the opportunity for their offspring to be able to add more offspring to their population in the future. However, many turtles do not make it to the ocean after hatching on the beach. To fix this problem green sea turtles produce more offspring than completely necessary so when some turtles don't make it to the ocean there are still enough survivors left.
Death: There are multiple reasons for the death of green sea turtles. The death of unborn or new born turtles by predators is the biggest cause in a decreasing population. Another factor that causes a decrease, but not death, is the capturing of the sea turtles for aquariums and exhibits.
Logistical Growth: Limited resources could have caused the green sea turtle population to begin with a small number. Then steadily resources came available and the reproduction rate increased causing an increase in population. Eventually the population reached a carrying capacity, which means the turtles environment could no longer support all of the individuals and the population flattened out.
Density Dependent Factors: Two density-dependent factors that affect the population of green sea turtles is the predation of turtles before they have hatched by egg-eating predators and the predation of new born turtles making their way to the ocean after hatching.
Density Independent Factors: Two density-independent factors that affect the population of green sea turtles is beach erosion which can make it difficult for turtles to come ashore and flooding which can cover nests and again make coming ashore very difficult.