Animals and plants introduced from foreign habitats may not reveal themselves to be harmful 'invasive' species for decades, according to a European study published on Monday. Canada geese walk towards the water at Cuckmere Haven in southern England in this February 22, 2006 file photo. REUTERS/Luke MacGregor Species that are moved away from their natural predators back home can displace native species in their new habitats, and scientists say the problem already costs Europe 12 billion euros ($16 billion) a year. The study, which is likely to hold true for other continents too, means that the seeds of future, perhaps bigger, problems have literally already been sown.