“Imagine a community with the following 5 trophic levels: plants, crickets, mice, snakes and hawks. Predict what would happen if more hawks entered the community through immigration.”
Communities eventually come to a point at which they are in balance-with their predators, prey, habitat, etc…. However, by introducing too much of a species or a new species, the community can be thrown of balance. Let’s bring some more hawks into our community of plants, crickets, mice, snakes and just enough hawks to throw it off balance.
Mice reproduce extremely fast and if not controlled can overrun an area. Our original hawks were keeping this under control, as were the snakes. However, if you introduce more hawks into the community, a sort of chain-reaction, not necessarily good, will occur.
First, the hawks will eat the snakes. Now there will be fewer snakes to hunt the mice. However, mice will also be eaten by the hawks.
This means either of two things. One, in case the mice do not get preyed upon lavishly by the hawks, the mice population will grow larger and larger, eating too many of the crickets. Crickets eat plants, so without them the plants will also be thrown off balance. The second option is that the hawks can eat too many of the mice, which could lead the cricket population to grow to large, eat too many plants, and throw the community off balance this way.
Throwing a community off balance is most often not a good thing, but you never know…..it could be good in the long-term.