Bomb shelters and refugee centres, I think
They were really into building ships later on and people liked them and wanted to buy them so i think that is the answer
As a direct result of the transatlantic slave trade, the greatest movement of Africans was to the Americas — with 96 per cent of the captives from the African coasts arriving on cramped slave ships at ports in South America and the Caribbean Islands.
The affect it has on the environment
It led to bubonic plague. It led to starvation.