so are humans, because of pollution and war, invasive species?
Indeed if an animal becomes extinct it is a good thing to introduce a similar foreign animal to perform the function of the lost animal to the local environment..
I thought that was obvious.
Yes, everything you've said sounds accurate. Eco-biologists and conservationists are concerned with true "invasive species" that dramatically alter the food chain or other resources within a particular ecosystem. The tiny snails invading northern lakes breed rapidly and deplete food resources, killing off the native snails and fish, and their shape and size makes them inedible, and therefore not a contributor to the food chain. European Starlings are spreading across the US as well, breeding rapidly and eating the bugs that would be consumed by the native birds. On top of that, they lay their eggs in the nests of other birds, often pushing out several eggs to make room for their own. The invading hatchling grows more rapidly than the hatchlings around it, and the adoptive momma bird feeds the loudest squawker more than she feeds her own babies, who often die of malnutrition.<br />
The greatest problem with introducing a new species to any environment is that we don't KNOW how everything is going to react until we see it in action, and often times, by then, it is too late.
The human is the most destructive and invasive animal to ever come along
I think if the animal over-produces and takes away from other species or introduces something negative to the environment then it is an invasive species. Starlings for example, it's hard to put a purple martin house around here without starlings taking over.
"An invasive species is an organism that causes ecological or economic harm in a new environment where it is not native."