Well I think the extermination of Indigenous people in the Americas, Africa, Australia and Oceanic islands is one, another is the Destruction of the Environment in those lands, another is the introduction of Invasive species like Rats, Cats, Dogs and Crows, into environments which were not resistant to the effects of these animals.
But if you ask WHY, did the Europeans have to go around the World, it is Because, the Islamic (Arabic and Turkish) Empires were blocking their Traditional Trade Routes.
So, it is the Islamic Empires which are to blame for the ill Effects of that age, just as the ISIS is largely responsible for the Immigrant crisis in Europe.
Thanks.