Dual role of human activities and climate in pre-industrial nitrogen shifts in Ireland
Bibliographic record
Abstract
Past research has uncovered a shift in herbivore collagen δ 15 N values during the Middle to Late Bronze Age (3700–2750 BP) in Ireland, attributed to intensified land-use - another example in a growing body of evidence that suggests that the Anthropocene concept (whereby humans have made significant impacts to the Earth's systems) began far earlier than previously thought (the ‘Palaeoanthropocene’). While human activity was clearly an important driver of this shift, it remains possible that climate may also have played a role. In Ireland, this shift in δ 15 N appeared to be sustained despite subsequent reforestation, suggesting that Bronze Age and later peoples left a profound biogeochemical mark on the environment. Here, we revisit this topic, presenting new stable isotope ( δ 15 N and δ 13 C) measurements from directly radiocarbon-dated wild and domesticated adult herbivorous ungulate bones from the Bronze and Iron Ages, with the aim of constraining the timing of this shift and disentangling the role of human land use from climatic influences. A sustained nitrogen isotopic shift was constrained to ca. 3000 cal BP. Notably, during the Iron Age, a time of widespread reforestation, wild and domesticated herbivorous ungulates exhibited δ 15 N values that were not significantly different from one another. This suggests that, while the δ 15 N shift was initiated by land-use change, climate variability, particularly shifts towards warmer and drier conditions during the Late Bronze/Iron Age transition and later Iron Age, may have contributed to its persistence. This study refines the chronology of nitrogen cycle changes in Ireland, demonstrating that human activity initiated a long-term shift in δ 15 N values during the Late Bronze Age, but that climatic factors may have played a role in maintaining elevated δ 15 N values during periods of reduced land use. These findings underscore the complexities of understanding the nitrogen cycle in ancient environments and highlight the potential interplay between anthropogenic and environmental drivers of biogeochemical change.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".