Anthropogenic changes to the Holocene nitrogen cycle in Ireland

Humans have always impacted their ecosystems, but finding early evidence of significant and lasting changes to landscapes is rare. Here we report on human-caused changes to the nitrogen cycle in Ireland in the Bronze Age, with intensification of agriculture resulting in lasting changes to the nitrogen isotope values of animals (wild and domesticates) during the Holocene. Through deforestation, land clearance and management, and more intensive animal husbandry and cereal crop cultivation in the later Bronze Age, major changes to the nitrogen inputs and cycling of the soil occurred and after this time the Irish landscape took the form it currently resembles. Within the debate concerning the onset of the Anthropocene, we suggest that these data shows that human activity in Ireland was significant enough in the Bronze Age to have lasting impacts, and therefore marks a profound shift in the relationship between humans and their environment.