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‘White gold’ guano fertilizer drove agricultural intensification in the Atacama Desert from ad 1000

Nature Plants volume 7, pages 152–158 (2021)Cite this article

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Abstract

The archaeological record shows that large pre-Inca agricultural systems supported settlements for centuries around the ravines and oases of northern Chile’s hyperarid Atacama Desert. This raises questions about how such productivity was achieved and sustained, and its social implications. Using isotopic data of well-preserved ancient plant remains from Atacama sites, we show a dramatic increase in crop nitrogen isotope values (δ15N) from around ad 1000. Maize was most affected, with δ15N values as high as +30‰, and human bone collagen following a similar trend; moreover, their carbon isotope values (δ13C) indicate a considerable increase in the consumption of maize at the same time. We attribute the shift to extremely high δ15N values—the highest in the world for archaeological plants—to the use of seabird guano to fertilize crops. Guano—‘white gold’ as it came to be called—thus sustained agricultural intensification, supporting a substantial population in an otherwise extreme environment.

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Fig. 1
Fig. 2: Stable isotope results for carbon and nitrogen (calibrated in relation to the international standards VPDB and AIR) in archaeological crops and wild plants.
Fig. 3: Modern, historical and archaeological images associated with seabird guano and crops.
Fig. 4: Boxplots showing variation in the isotope composition of carbon and nitrogen (calibrated in relation to the international standards VPDB and AIR) in different tissues from archaeological human samples from coastal, inland and Precordillera sites dating to the Formative, Middle, Late Intermediate and Late Periods.

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The authors declare that all data generated or analysed during this study are included in this published article (and its Supplementary Information files).

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Acknowledgements

We thank the National Geographic Society for Early Career grant nos. EC-53250R-18, FONDECYT 3180317, 1181829 and 1191452 and the Becas Chile-PhD Scholarship for funding support. C.H. is supported by Nucleo Milenio INVASAL funded by Chile’s government programme, Iniciativa Científica Milenio from the Ministerio de Ministerio de Ciencia, Tecnología, Conocimiento e Innovación. C.L. acknowledges support from grant no. ANID PIA CCTE AFB170008 and Nucleo Milenio UPWELL. We are grateful to P. Ditchfield, T. Higham, D. Chival, J. Cameron and F. Docmac for their help in the laboratory. We thank S. Santana-Sagredo for helping and improving the figures of this article. We are also grateful to the institutions that allowed us sampling their archaeological collections. All samples were analysed at the University of Oxford under Chilean government permit (no. 42.649, CVE 1757327, Diario Oficial de la República de Chile).

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Author notes

  1. Francisca Santana-Sagredo

    Present address: Escuela de Antropología, Pontificia Universidad Católica de Chile, Santiago, Chile, Santiago, Chile

Authors and Affiliations

  1. Escuela de Antropología, Pontificia Universidad Católica de Chile, Santiago, Chile

    Francisca Santana-Sagredo & Virginia B. McRostie

  2. Universidad de Antofagasta Stable Isotope Facility, Instituto Antofagasta, Universidad de Antofagasta, Angamos, Antofagasta, Chile

    Francisca Santana-Sagredo & Chris Harrod

  3. School of Archaeology, University of Oxford, Oxford, UK

    Francisca Santana-Sagredo, Rick J. Schulting & Julia Lee-Thorp

  4. Departamento de Prehistoria, Programa de Doctorado en Arqueología Prehistórica, Universidad Autónoma de Barcelona, Barcelona, Spain

    Pablo Méndez-Quiros

  5. Programa de Doctorado en Biología, mención Ecología, Pontificia Universidad Católica de Chile, Santiago, Chile

    Ale Vidal-Elgueta

  6. Departamento de Antropología, Universidad de Chile, Santiago, Chile

    Mauricio Uribe & Anahí Maturana-Fernández

  7. Instituto de Arqueología y Antropología (IIA), Universidad Católica del Norte (UCN), San Pedro de Atacama, Chile

    Rodrigo Loyola

  8. UMR 7055 Prehistoire et Technologie (PreTéch), Université Paris Ouest Nanterre La, Défense, France

    Rodrigo Loyola

  9. Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago, Chile

    Francisca P. Díaz

  10. Centro del Desierto de Atacama, Pontificia Universidad Católica de Chile, Santiago, Chile

    Claudio Latorre & Virginia B. McRostie

  11. Departamento de Ecología, Pontificia Universidad Católica de Chile, Santiago, Chile

    Claudio Latorre

  12. Institute of Ecology and Biodiversity, Pontificia Universidad Católica de Chile, Santiago, Chile

    Claudio Latorre

  13. Instituto de Alta Investigación, Universidad de Tarapacá, Arica, Chile

    Calogero M. Santoro

  14. Programa de Magíster en Antropología, Departamento de Antropología, Universidad de Tarapacá, Arica, Chile

    Valentina Mandakovic

  15. Núcleo Milenio INVASAL, Concepción, Chile

    Chris Harrod

  16. Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile

    Chris Harrod

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  1. Francisca Santana-Sagredo
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Contributions

F.S.-S., R.J.S. and J.L.-T. came up with the original idea and research design. F.S.-S., P.M.-Q., A.V.-E., M.U., R.L. and A.M.-F. conducted and participated in the fieldwork. F.S.-S., A.V.-E. and A.M.-F. carried out sampling in universities and museum collections. A.V.-E., V.B.M., V.M. and F.P.D. undertook taxonomic analysis of crops and wild fruits. F.S.-S. and A.M.-F. conducted sample processing and laboratory work. F.S.-S and P.M.-Q collected information and worked on the human isotope and radiocarbon dates databases. F.S.-S., R.J.S. and C.H. undertook the statistical analysis. R.L. designed the map. F.S.-S., J.L.-T., R.J.S. and C.H. interpreted the results. C.L. and C.M.S. contributed to interpreting the data based on the local ecology and archaeology. F.S.-S. wrote the paper with the help of R.J.S. and J.L.-T. All the authors commented on the paper.

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Correspondence to Francisca Santana-Sagredo.

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Santana-Sagredo, F., Schulting, R.J., Méndez-Quiros, P. et al. ‘White gold’ guano fertilizer drove agricultural intensification in the Atacama Desert from ad 1000. Nat. Plants 7, 152–158 (2021). https://doi.org/10.1038/s41477-020-00835-4

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