The Norse colonisation or landnám of the North Atlantic islands of the Faroes, Iceland, and Greenland from the ninth century AD onwards provides opportunities to examine human environmental impacts on ‘pristine’ landscapes on an environmental gradient from warmer, more maritime conditions in the east to colder, more continental conditions in the west. This paper considers key environmental contrasts across the Atlantic and initial settlement impacts on the biota and landscape. Before landnám, the modes of origin of the biota (which resulted in boreo-temperate affinities), a lack of endemic species, limited diversity, and no grazing mammals on the Faroes or Iceland, were crucial in determining environmental sensitivity to human impact and, in particular, the impact of introduced domestic animals. Gathering new data and understanding their geographical patterns and changes through time are seen as crucial when tackling fundamental questions about human interactions with the environment, which are relevant to both understanding the past and planning for the future.