Forecasting Andean rainfall and crop yield from the influence of El Niño on Pleiades visibility


Farmers in drought-prone regions of Andean South America have historically made observations of changes in the apparent brightness of stars in the Pleiades around the time of the southern winter solstice in order to forecast interannual variations in summer rainfall and in autumn harvests. They moderate the effect of reduced rainfall by adjusting the planting dates of potatoes, their most important crop1. Here we use data on cloud cover and water vapour from satellite imagery, agronomic data from the Andean altiplano and an index of El Niño variability to analyse this forecasting method. We find that poor visibility of the Pleiades in June—caused by an increase in subvisual high cirrus clouds—is indicative of an El Niño year, which is usually linked to reduced rainfall during the growing season several months later. Our results suggest that this centuries-old method2 of seasonal rainfall forecasting may be based on a simple indicator of El Niño variability.

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Figure 1: Correlations with central Andean high cloud in late June.
Figure 2: A diagram of the stars in the Pleiades of visual magnitude 6.0 or brighter.
Figure 3: Central Andean rainfall anomalies and El Niño.
Figure 4: Central Andean harvests and El Niño.


  1. 1

    Zimmerer,K. S. Changing Fortunes: Biodiversity and Peasant Livelihood in the Peruvian Andes (Univ. California Press, Berkeley, 1996).

  2. 2

    Salomon,F. & Urioste,G. L. The Huarochiri Manuscript: A Testament of Ancient and Colonial Andean Religion (Univ. Texas Press, Austin, 1991 [c. 1608]).

  3. 3

    Ballón Aguirre,E., Cerrón Palomino,R. O. & Chambi Apaza,E. Vocabulario Razonado de la Actividad Agraria Andina. Terminología Agraria Quechua. (Centro de Estudios Regionales Andinos “Bartolomé de Las Casas”, Cusco, 1992).

  4. 4

    Urton,G. At the Crossroads of the Earth and The Sky: An Andean Cosmology (Univ. Texas Press, Austin, 1981).

  5. 5

    Grillo Fernández,E., Quiso Choque,V., Rengifo Vásquez,G. & Valladolid Rivera,J. Crianza Andina de la Chacra (Proyecto Andino de Tecnología Campesina, Lima, 1994).

  6. 6

    Mishkin,B. Cosmological ideas among the Indians of the southern Andes. J. Am. Folklore 53, 225–241 (1940).

  7. 7

    Morote Best,E. La fiesta de San Juan, el Bautista. Arch. Peruanos Folklore 1, 160–200 (1953).

  8. 8

    Orlove,B. S. Two rituals and three hypotheses: an examination of solstice divination in southern highland Peru. Anthropol. Quart. 52, 86–98 (1979).

  9. 9

    Lira,J. A. Farmacopea Tradicional Indígena y Prácticas Rituales (El Condor, Lima, 1946).

  10. 10

    Camino,A., Recharte,J. & Bidegaray,P. La Tecnología en el Mundo Andino. Runakunap Kawsayninkupaq Rurasqankunaqa Vol. 1 (eds Lechtman, H. & Soldi, A. M.) 261–281 (Universidad Nacional Autónoma de México, Mexico City, 1981).

  11. 11

    Goland,C. Cultivating Diversity: Field Scattering as Agricultural Risk Management in Cuyo Cuyo, Dept. of Puno, Peru (Working Paper No. 4, Research Project on Production, Storage and Exchange in a Terraced Environment on the Eastern Andean Escarpment, Department of Anthropology, Univ. North Carolina, Chapel Hill, 1992).

  12. 12

    Kolata,A. Valley of the Spirits: A Journey into the Lost Realm of the Aymara (Wiley, New York, 1996).

  13. 13

    Carter,W. E. & Mamani,M. Irpa Chico: Individuo y Comunidad en la Cultura Aymara (Juventud, La Paz, 1982).

  14. 14

    Mamani,M. in Raíces de América: el Mundo Aymara (ed. Albó, X.) 75–131 (Alianza, Madrid, 1988).

  15. 15

    Yampara Huarachi,S. in La Cosmovisión Aymara (eds van den Berg, H. & Schiffers, N.) 143–186 (UCB/HISBOL, La Paz, 1992).

  16. 16

    Kraft,K. E. Andean Fields and Fallow Pastures: Communal Land Use Management under Pressures for Intensification. Thesis, Univ. Florida (1995).

  17. 17

    Beukema,H. P. & van de Zaag,D. E. Introduction to Potato Production (Pudoc, Wageningen, 1990).

  18. 18

    MacKerron,D. K. L. & Jeffries,R. A. The distribution of tuber sizes in droughted and irrigated crops of potato. I. Observations on the effect of water stress on graded yields from differing cultivars. Potato Res. 31, 269–278 (1988).

  19. 19

    Bauer,B. S. & Dearborn,D. S. P. Astronomy and Empire in the Ancient Andes: The Cultural Origins of Inca Sky Watching. (Univ. Texas Press, Austin, 1995).

  20. 20

    de Arriaga,P. J. The Extirpation of Idolatry in Peru (Univ. Kentucky Press, Lexington, 1968 [1621]).

  21. 21

    Anonymous Jesuit priest Misión de las provincias de los Huachos y Yauyos. Rev. Histórica (Lima) 6, 180–197 (1919).

  22. 22

    de Santillán,F., Valera,B. & Pachacuti,J. de S. C. Tres Relaciones de Antigüedades Peruanas (Guaranía, Asunción, 1950).

  23. 23

    Rossow,W. B. & Schiffer,R. A. ISCCP cloud data products. Bull. Am. Meteorol. Soc. 72, 2–20 (1991).

  24. 24

    Kent,G. S. et al. Surface temperature related variations in tropical cirrus cloud as measured by SAGE II. J. Clim. 8, 2577–2594 (1995).

  25. 25

    Liao,X., Rossow,W. B. & Rind,D. Comparison between SAGE II and ISCCP high-level clouds 1. Global and zonal mean cloud amounts. J. Geophys. Res. 100, 1121–1135 (1995).

  26. 26

    Kalnay,E. et al. The NCEP/NCAR 40 year reanalysis project. Bull. Am. Meteorol. Soc. 77, 437–471 (1996).

  27. 27

    Schaefer,B. E. Astronomy and the limits of vision. Vistas Astron. 36, 311–361 (1993).

  28. 28

    Thompson,L. G., Mosley-Thompson,E. & Arnao,B. J. El Niño-Southern Oscillation events recorded in the stratigraphy of the tropical Quelccaya ice cap, Peru. Science 226, 50–53 (1984).

  29. 29

    Aceituno,P. On the functioning of the Southern Oscillation in the South American sector. Part I: Surface climate. Mon. Weath. Rev. 116, 505–524 (1988).

  30. 30

    Frisancho,A. R. et al. Developmental, genetic and environmental components of aerobic capacity at high altitude. Am. J. Phys. Anthropol. 96, 431–442 (1995).

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We thank G. Urton for insights into Andean ethnoastronomy, G. Rasmussen for discussions on visibility and cirrus cloud, G. Scott for providing potato yield data for Puno department, Peru, and R. Bishop, K. Cook, D. Dearborn, D. Helfand, A. Kaplan, G. Kiladis, J. Lenters, M. Sarazin and B. Schafer for comments. M.A.C. thanks B. D'Achille for first making him aware of the Andean forecasting scheme.

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Correspondence to Benjamin S. Orlove.

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Orlove, B., Chiang, J. & Cane, M. Forecasting Andean rainfall and crop yield from the influence of El Niño on Pleiades visibility. Nature 403, 68–71 (2000).

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