When adults are long-lived, a population can maintain itself or grow even with low recruitment. For example, consider a pair of snow geese which live to be eight years old, the average lifespan of snow geese at LaPerouse Bay. To maintain the population, these geese would need to add only two reproducing birds into the population during their lifetime. Adding four reproducing birds to the population during their lifetime provides a rate of population growth that doubles the population every eight years. Eight years is the average lifespan.
Many birds live to be much older.
We don't know. Critical and fragile arctic habitats will continue to be destroyed at an accelerated rate as snow goose colonies expand to other marginal habitats. This will impact not only snow geese, but all other species. Eventually, food resources could become so limited that production could not maintain the population. The age structure of the population will continue to shift toward a higher percentage of older birds - a highly unstable situation.