A few examples of historical intervention:
The first barge came through the Erie Canal (joining Lake Erie to the Atlantic Ocean) and arrived in New York's harbour. To celebrate, the barge transported a keg of water from Lake Erie which was dumped into the harbour along with vials of water from the Nile, Thames, Seine, Ganges, and Rhine rivers. This event foreshadowed the large-scale contaminations, due to ship ballast waters, that occur today.
In 1870, Spencer Baird of the US Fish Commission decided to improve the fish fauna of the United States by importing a delectable species of Eurasian carp. It was instantly successful. Carp were shipped throughout the country and started reproducing with a vengeance. However, these bottom feeding fish destroy natural habitat and are no longer considered a delicacy.