Daniel H. Janzen

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Dan Janzen and Winnie Hallwachs, at the American Museum of Natural History, 1998

Daniel Hunt Janzen (born January 18, 1939 in Milwaukee, Wisconsin, U.S.)[1] is an evolutionary ecologist, biologist, conservationist. He divides his time between his professorship in biology at the University of Pennsylvania (Philadelphia, USA), where he has been since 1976, and his research and field work in Costa Rica, where he is an ad honorem (without remuneration) technical advisor for two long-term and long-range projects, which he conceived and initiated in the early 1970s: Area de Conservación Guanacaste, one of the oldest, largest and most successful habitat restoration project in the world, 1.430 km², located just south of the Costa Rica-Nicaragua border, between the Pacific Ocean and the Cordillera de Tilaran; and the Instituto Nacional de Biodiversidad (INBio), a research organisation that has taken the task of inventorying, cataloguing and describing the country's gigantic natural endowment. He has been influential in the creation of a "model" park, the Area de Conservacion Guanacaste in Costa Rica's northern region of Guanacaste. This park exemplifies Dr. Janzen's beliefs about how a park should be run. It is known for being the site of considerable biological research and for forest restoration and community outreach.

Early career[edit]

Janzen obtained his B.Sc. degree in Biology from the University of Minnesota, Minneapolis in 1961, and his Ph.D. from the University of California, Berkeley, in 1965. In 1963 he attended as a student a two-month course in tropical biology taught in several field sites throughout Costa Rica. This Advanced Science Seminar in Tropical Biology was the precursor for Fundamentals in Tropical Biology course offered by the Organization for Tropical Studies (OTS), a consortium of several North American and Costa Rican universities. He went back in 1965 as an instructor and has lectured in at least one of the three yearly courses every year since. Before joining the faculty at the University of Pennsylvania he taught at the University of Kansas (1965–1968), the University of Chicago (1969–1972) and at the University of Michigan (1972–1976). Janzen has also held teaching positions in Venezuela (Universidad de Oriente, Cumaná in 1965-66; Universidad de los Los Andes, Mérida in 1973), and in Puerto Rico (Universidad de Puerto Rico, Río Piedras, 1969). Through these teaching positions, continuous association with OTS, and numerous publications, Janzen has been in contact with and influenced the thinking and ideas of many of the researchers and students of tropical ecology and conservation in the western hemisphere during the last 40 years.

Research, from theory to praxis and back to theory[edit]

Janzen's work exemplifies the dialectic method of research applied to the biology of the natural world. For him it has not been the passive analysis of documents and data about ecological processes in order to formulate theories, but rather the active creation of life size scenarios of ecological change and their careful and meticulous documentation from which he then formulates theories which inspire new grand experiments in an ever-expanding spiral of knowledge based on the keen observation of nature. The following sections are an attempt to synthesise the main themes of his lifelong quest and work.

Coevolution of plants and animals[edit]

Tropical habitat restoration[edit]

Tropical dry forests are the world's most threatened forest ecosystems. In middle America there were 550 000 km² of dry forests at the beginning of the 16th century; today, less than 0.08% (440 km² ) remains. They have been cleared, burnt and replaced by pastures for cattle raising, at an ever-faster rate during the last 500 years. However, beginning in the early 1970s, Janzen dreamed of a project to grow back some 700 km² of natural, pre-Columbian habitat in Guanacaste, in order to integrate four different national parks which together house at least 15 different biotopes, viz (mangroves, dry forest and shrubs, ephemeral, rainy season, and permanent streams, fresh water and littoral swamps, evergreen rain- and cloud forests…) and ca. 4% from world's plant, mammals, birds, reptiles, amphibians, fishes and insects diversity, all within an area less than 1 500 km². This is Área de Conservación Guanacaste (ACG).[2]

Habitat restoration is not a simple matter, not only must one fight against hundreds of years of ecological degradation, manifested in the form of altered drainage patterns, hard to eradicate pastures, compacted soils, exhausted seed banks, diminished adult and propagule stocks, proliferation of fire-resistant and unpalatable weeds from the old world tropics and sub-tropics, et cetera, but also one is faced with the difficulties of changing a culture which coevolved with, profited from and can become miserable with such a system. For this reason ACG was conceived as a cultural restoration project as well, which, to paraphrase its natural counterpart, ought to be grown as well. ACG rests on three complementary processes that integrate experimentation, habitat restoration and cultural development, to speed up succession:

  • Active restoration, artificial dispersal of propagules from plant species native to the Guanacaste habitats
  • Passive restoration by means of fire, anti-poaching and hervivory control
  • Ecological education and sensibilisation

Honorary distinctions[edit]

Janzen has been subject to recognition many times in the USA, as well as in Europe and Latin America; the monetary endowments of these prizes have been invested in the trust fund of the ACG or another of his conservation's projects in Costa Rica; amongst the 19 prizes and distinctions, the following are the most important:

See also[edit]


The following are just a couple of the publications by Janzen not otherwise listed.

  • Rosenthal, Gerald A., & Janzen, Daniel H. (editors) (1979), Herbivores: Their Interaction with Secondary Plant Metabolites, New York: Academic Press, p. 41, ISBN 0-12-597180-X
  • Janzen, Daniel H. (editor) (1983), Costa Rican Natural History, Chicago: University of Chicago Press, p. 823, ISBN 9780226393346


  1. ^ Profile of Daniel H. Janzen
  2. ^ Janzen, Daniel H. 1986. Guanacaste National Park: Tropical Ecological and Cultural Restoration. Editorial Universidad Estatal a Distancia/ FundaciónTinker/Fundación Parque Nacionales/103 pp. San José, Costa Rica.
  3. ^ "The Four Awards Bestowed by The Academy of Natural Sciences and Their Recipients". Proceedings of the Academy of Natural Sciences of Philadelphia. The Academy of Natural Sciences of Philadelphia. 156 (1): 403–404. June 2007. doi:10.1635/0097-3157(2007)156[403:TFABBT]2.0.CO;2.
  4. ^ "Albert Einstein World Award of Science 2002". Archived from the original on June 7, 2014. Retrieved August 13, 2013.


  • Janzen, D. H. 1966. Coevolution of mutualism between ants and acacias in Central America. Evolution: 20(3) 249-275
  • Janzen, D. H. 1985. Spondias mombin is Culturally Deprived in Megafauna-Free Forest. Journal of Tropical Ecology 1:131–155.
  • Janzen, D. H. 1986. Guanacaste National Park: Tropical Ecological and Cultural Restoration. Editorial Universidad Estatal a Distancia/ FundaciónTinker/Fundación Parque Nacionales/103 pp. San José, Costa Rica.
  • Allen, William. Green Phoenix. New York: OUP, 2001. Print.

External links[edit]