Answer: In a simple sense, growth in population is a good thing as it means that a species is thriving and doing well in its environment as well as reproducing at desirable rates. However, if population continues and continues to grow it will eventually reach a cap where an environment can no longer hold more members of that specific species because there is a limit on food and places of shelter. This leads to natural rises and declines in a species over time (which can be very predictable as well.) A downside to rapid and sustained population growth is that if a species keeps growing and growing without reaching its cap (which happens a lot with introduced species into an environment which were not there naturally) is that they can overrun and destroy a natural environment and damage the ecosystem. Animals and species which are already there can have their population numbers drastically reduced because of this invasive species and may be forced to move to a new area.