Global growth and stability of agricultural yield decrease with pollinator dependence
Edited by Gretchen C. Daily, Stanford University, Stanford, CA, and approved February 28, 2011 (received for review August 23, 2010)
Abstract
Human welfare depends on the amount and stability of agricultural production, as determined by crop yield and cultivated area. Yield increases asymptotically with the resources provided by farmers’ inputs and environmentally sensitive ecosystem services. Declining yield growth with increased inputs prompts conversion of more land to cultivation, but at the risk of eroding ecosystem services. To explore the interdependence of agricultural production and its stability on ecosystem services, we present and test a general graphical model, based on Jensen's inequality, of yield–resource relations and consider implications for land conversion. For the case of animal pollination as a resource influencing crop yield, this model predicts that incomplete and variable pollen delivery reduces yield mean and stability (inverse of variability) more for crops with greater dependence on pollinators. Data collected by the Food and Agriculture Organization of the United Nations during 1961–2008 support these predictions. Specifically, crops with greater pollinator dependence had lower mean and stability in relative yield and yield growth, despite global yield increases for most crops. Lower yield growth was compensated by increased land cultivation to enhance production of pollinator-dependent crops. Area stability also decreased with pollinator dependence, as it correlated positively with yield stability among crops. These results reveal that pollen limitation hinders yield growth of pollinator-dependent crops, decreasing temporal stability of global agricultural production, while promoting compensatory land conversion to agriculture. Although we examined crop pollination, our model applies to other ecosystem services for which the benefits to human welfare decelerate as the maximum is approached.
Acknowledgments
Research was funded by Agencia Nacional de Promoción Científica y Tecnológica Grant 2007-01300, Consejo Nacional de Investigaciones Científicas y Técnicas Grant PIP 01623, Universidad Nacional del Comahue Grant B152/04, and by the Natural Sciences and Engineering Research Council of Canada. L.A.G. was supported by the German Academic Exchange Program and S.A.C. by the Commonwealth Scientific and Industrial Research Organization's Sustainable Agriculture Flagship.
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Cover image: Pictured is a simulated spatial distribution of disease risks, overlaid onto a base map of North America, retrieved March 11, 2011, from Google Maps. Pink and red colors indicate simulated hotspots of high disease risk clustering. The image was created using exploratory spatial analytic software services that utilize networked computers provided by the National Science Foundation TeraGrid and the Open Science Grid to support interactive and data-intensive research. In the introduction to this PNAS Special Feature, Dawn J. Wright and Shaowen Wang discuss how spatial cyberinfrastructure facilitates scientific discoveries through streamlined collaboration and computation and make predictions for its impact on the future. See the article by Wright and Wang on pages 5488–5491. Image courtesy of Shaowen Wang and Yan Liu (University of Illinois at Urbana-Champaign, Urbana, IL).
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Freely available online through the PNAS open access option.
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Published online: March 21, 2011
Published in issue: April 5, 2011
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Acknowledgments
Research was funded by Agencia Nacional de Promoción Científica y Tecnológica Grant 2007-01300, Consejo Nacional de Investigaciones Científicas y Técnicas Grant PIP 01623, Universidad Nacional del Comahue Grant B152/04, and by the Natural Sciences and Engineering Research Council of Canada. L.A.G. was supported by the German Academic Exchange Program and S.A.C. by the Commonwealth Scientific and Industrial Research Organization's Sustainable Agriculture Flagship.
Notes
This article is a PNAS Direct Submission.
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Competing Interests
The authors declare no conflict of interest.
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