A twofold example of Invasion Biology.

In 1936, the giant African snail was introduced to Hawaii. These snails have pretty shells, so they make for nice garden decorations. But within ten years, the giant African snail became a major pest throughout the Hawaiian Islands.

To combat the damage caused by the giant African snail, in 1955 the Hawaii State Department of Agriculture decided to introduce the rosy wolfsnail, a carnivorous snail native to the Southern United States,

What they didn't fully realize is that wolfsnails are not just predators, but they are voracious eaters and they're very fast (for snails, anyway). They also have a high reproductive rate. The wolfsnail hunted the giant African snail, but they also viciously hunted all of the local species, including the Oahu tree snail. In less than a year, the wolf snail hunted many of the indigenous Hawaiian tree snails to extinction.

To date, the Oahu tree snails remain an endangered species. The rosy wolfsnails still remain a problem.

http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Euglandina_rosea.html