Colorado beetle, Rats and Rabbits

More often, however, species are introduced accidentally and have a negative impact. The Colorado beetle was introduced to Europe from North America and has been damaging potato crops in Europe ever since. Rats originated from Asia and spread to Europe and the Americas as unwanted passengers on trade ships. The expansion of the Roman Empire was the reason for rabbits spreading north from Spain to the rest of Europe. Centuries later, in 1849, when Europeans were exploring the continent of Australia, rabbits were introduced and have caused serious problems ever since.