Daniel Janzen

Professor of Biology; Thomas G. and Louise E. DiMaura Term Chair
301 Leidy Laboratories
Ecology and Biodiversity

Ph.D., University of California, Berkeley, 1965

Research Interests: 


ecology and biodiversity of ecosystems


Why do caterpillars eat the plants they eat? Why do parasitoids (wasps and flies) eat the caterpillars they eat? And why do they do it that way in a complex dry forest, rain forest and cloud forest in northwestern Costa Rica? I have long pursued these questions because I am curious about them and their answers. But the answers, and the research processes themselves, also have very broad application to how one may use the biodiversity of a conserved tropical wildland without destroying it - biodiversity development.


How can we insure that tropical wildlands, and all of their biodiversity, are still with us centuries from now? Through non-destructive use of lands explicitly allocated to this land use. But to use biodiversity without damage requires detailed natural history knowledge, tracking of demography, and ecosystem-level understanding. And to use requires a user.


So it is that very basic research on the interactions of animals and plants in complex tropical forest quite serendipituously finds itself being key intellectual infrastructure and technological know-how for biodiversity prospecting, biological control of pests, biotechnology, ecotourism development, biocultural education, environmental monitoring, silviculture, agriculture and very much more - all the kinds of things that have to accompany conservation of large tropical wildlands.


My research over the past 55 years has evolved from a Victorian study of natural history of tropical animal-plant interactions to an exploration of the ecology of the interface between society and tropical wildland biodiversity. The administrative structure of institutions such as wildland administrations and Ministries of the Environment, the biodiversity development of conserved wildlands to where they can pay their own direct costs, and the integration of wildlands into society, are all major and essential tools in the engineering of the tropical countryside. Costa Rica as a whole is the ecosystem, and Area de Conservacion Guanacaste, in the northwestern corner, is the place.


My research is done where the organisms are, i.e., Costa Rica.

Selected Publications: 
Publication Featuring Dr. Janzen and His Research
Wolf, G. 2008. Barcode of Life. Wired 16(10)(October):200-212.
Publications by Dr. Janzen
Smith, M.A., Rodriguez, J.J., Whitfield, J.B., Deans, A.R., Janzen, D.H., Hallwachs, W., and Hebert, P.D.N. 2008. Extreme diversity of tropical parasitoid wasps exposed by iterative integration of natural history, DNA barcoding, morphology, and collections. Proceedings of the National Academy of Sciences 105:12359-12364.
Burns, J.M., Janzen, D.H., Hajibabaei,M., Hallwachs,W., and Hebert, P.D.N. 2008. DNA and cryptic species of skipper butterflies in the genus Perichares in Area de Conservacion Guanacaste, Costa Rica. Proceedings of the National Academy of Sciences 105:6350-6355.
Miller, J. C., Janzen, D. H. and Hallwachs, W. 2007. 100 Butterflies and moths. Harvard University Press, Cambridge, Massachusetts. 256 pp.
Smith, M. A., Woodley, N. E., Janzen, D. H., Hallwachs, W., and Hebert, P. D. N. 2006. DNA barcodes reveal cryptic host-specificity within the presumed polyphagous members of a genus of parasitoid flies (Diptera: Tachinidae). Proceedings of the National Academy of Sciences 103:3657-3662.
Miller, J. C., Janzen, D. H. and Hallwachs, W. 2006. 100 Caterpillars. Harvard University Press, Cambridge, Massachusetts. 264 pp.
Janzen, D. H. 2005. How to conserve wild plants? Give the world the power to read them. Forward, Plant conservation: a natural history approach, eds. Krupnick, G. and Kress, J., University of Chicago Press, Chicago, 346 pp.
Janzen, D. H., Hajibabaei, M., Burns, J. M., Hallwachs, W., Remigio, E. and Hebert, P. D. N. 2005. Wedding biodiversity inventory of a large and complex Lepidoptera fauna with DNA barcoding. Philosophical Transactions of the Royal Society B 360 (1462):1835-1846.
Hebert, P. D. N., Penton, E. H., Burns, J. M., Janzen, D. H. and Hallwachs, W. 2004. Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator. Proceedings of the National Academy of Sciences 101:14812-14817.
Janzen, D. H. 2002. Tropical dry forest: Area de Conservación Guanacaste, northwestern Costa Rica. In Handbook of Ecological Restoration, Volume 2, Restoration in Practice, eds. Perrow, M. R., Davy, A. J., Cambridge University Press, Cambridge, UK, pp. 559-583.
Schauff, M. E. and Janzen, D. H. 2001. Taxonomy and ecology of Costa Rican Euplectrus (Hymenoptera: Eulophidae), parasitoids of caterpillars (Lepidoptera). Journal of Hymenoptera Research 10(2):181-230.
Janzen, D. H. 2001. Saving fractured oases of biodiversity (book review). Quarterly Review of Biology 76:327-330.
Burns, J. M. and Janzen, D. H. 2001. Biodiversity of pyrrhopygine skipper butterflies (Hesperiidae) in the Area de Conservación Guanacaste, Costa Rica. Journal of the Lepidopterist's Society 55:15-43.
Janzen, D. H. 2000. Wildlands as gardens. National Parks Magazine 74(11-12):50-51.
Janzen, D. H. 2000. Costa Rica's Area de Conservación Guanacaste: a long march to survival through non-damaging biodevelopment. Biodiversity 1(2):7-20.
Janzen, D. H. 1999. Gardenification of tropical conserved wildlands: Multitasking, multicropping, and multiusers. PNAS 96(11):5987-5994.
Janzen, D. H. 1999. La sobrevivencia de las areas silvestres de Costa Rica por medio de su jardinificación. Ciencias Ambientales No. 16:8-18.
Janzen, D. H. 1998. Gardenification of wildland nature and the human footprint. Science 279:1312-1313.
Janzen, D. H. and I. D. Gauld 1997. Patterns of use of large moth caterpillars (Lepidoptera: Saturniidae and Sphingidae) by ichneumonid parasitoids (Hymenoptera) in Costa Rican dry forest. In Forests and Insects, eds. A. D. Watt, N. E. Stork and M. D. Hunter, Chapman & Hall, London, pp. 251-271.
Reid, W. V., S. A. Laird, R. Gómez, A. Sittenfeld, D. H. Janzen, M. A. Gollin and G. Juma. 1993. Biodiversity Prospecting. World Resources Institute, Washington, D.C. 341 pp.
Janzen, D. H. 1993. Caterpillar seasonality in a Costa Rican dry forest. In: Caterpillars. Ecological and evolutionary constraints on foraging, N. E. Stamp and T. M. Casey, eds., Chapman and Hall, New York, pp. 448-477.
Janzen, D. H. 1988. Guanacaste National Park: tropical ecological and biocultural restoration. In Rehabilitating Damaged Ecosystems, vol. 11, pp. 143-192, J. Cairns, Jr., ed., CRC Press, Boca Raton, Florida.
Janzen, D. H. 1986. The future of tropical ecology. Ann. Rev. Ecol. Syst. 17, 305-24.
Janzen, D. H. ed. 1983. Costa Rican Natural History, University of Chicago Press, Chicago, 816 pp.