ⓘ Daniel H. Janzen


ⓘ Daniel H. Janzen

Daniel Hunt Janzen is an American evolutionary ecologist, and conservationist. He divides his time between his professorship in biology at the University of Pennsylvania, where he is the DiMaura Professor of Conservation Biology, and his research and field work in Costa Rica.

In Costa Rica, Janzen and his partner Winifred Hallwachs helped to establish the Area de Conservacion Guanacaste World Heritage Site, one of the oldest, largest and most successful habitat restoration projects in the world. As of 2019, it consists of 169.000 hectares 420.000 acres, located just south of the Costa Rica-Nicaragua border, between the Pacific Ocean and the Cordillera de Tilaran. The park exemplifies their beliefs about how a park should be run. It is known as a center of biological research, forest restoration and community outreach.

Closely related is their work cataloguing the biodiversity of Costa Rica. Through a DNA barcoding initiative with geneticist Paul Hebert, they have registered over 500.000 specimens representing more than 45.000 species from Area de Conservacion Guanacaste. This research has led to the identification of cryptic species of near-identical appearance that differ in terms of genetics and ecological niche. Janzen and Hallwachs have supported species barcoding initiatives at both national and international levels through the Instituto Nacional de Biodiversidad INBio, CBOL Consortium for the Barcode of Life and iBOL International Barcode of Life.


1. Early career

Daniel Hunt Janzen was born January 18, 1939 in Milwaukee, Wisconsin. His father, Daniel Hugo Janzen, grew up in a Mennonite farming community and served as Director of the United States Fish and Wildlife Service. His father and mother, Miss Floyd Clark Foster of Greenville, South Carolina, were married on April 29, 1937.

Janzen obtained his B.Sc. degree in biology from the University of Minnesota, in 1961, and his Ph.D. from the University of California, Berkeley in 1965.

In 1963, Janzen attended 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 to a Fundamentals in Tropical Biology course which Janzen designed for the Organization for Tropical Studies OTS, a consortium of several North American and Costa Rican universities. Janzen went back in 1965 as an instructor and has lectured in at least one of the three yearly courses every year since.

Janzen taught at the University of Kansas 1965–1968, the University of Chicago 1969–1972 and at the University of Michigan 1972–1976 before joining the faculty at the University of Pennsylvania. Janzen has also held teaching positions in Venezuela, and in Puerto Rico.


2. Research

Janzens early work focused on the careful and meticulous documentation of species in Costa Rica, and in particular on ecological processes and the dynamics and evolution of animal-plant interactions. Miguel Altieri in his textbook Agroecology: The Science of Sustainable Agriculture says: "Janzens 1973 article on tropical agroecosystems was the first widely read evaluation of why tropical agricultural systems might function differently from those of the temperate zones".

In 1985, realizing that the area in which they worked was threatened, Janzen and Hallwachs expanded the focus of their work to include tropical forest restoration, expansion through land purchases and conservation.


2.1. Research Coevolution of plants and animals

  • Spondias mombin Anacardiaceae lost its megafauna seed dispersors in the Pleistocene. Between fire in open pastures and seed predation by bruchid beetles in closed-canopy forest, S. mombin does not stand a chance. But, today, in Guanacaste, seeds are dispersed by White-tailed deer Odocoileus virginianus and some 15 other mammals, that feed mostly in forest edges, where bruchids are less likely to find the seeds and fires are not so frequent.
  • Coevolution of a mutualistic system in New World tropics between species of Acacia Mimosoideae; Leguminosae, v. gr., Acacia cornigera, and the ant Pseudomyrmex ferruginea Formicidae. Acacia spp in the Neotropics are protected by ants against defoliation; for this, the ants are rewarded by means of special organs and physiology that Acacia has evolved.

2.2. Research Tropical habitat restoration

Tropical dry forests are the worlds 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.

In 1985, realizing that widespread development in northwestern Costa Rica was rapidly decimating the forest in which they conducted their research, Janzen and Hallwachs expanded the focus of their work. They began with the Parque Nacional Santa Rosa, which included 100 km 2 25.000 acres of pasture and relictual neotropical dry forest and 230 km 2 57.000 acres of marine habitat. This eventually became the Area de Conservacion Guanacaste ACG, which integrated four different national parks which together house at least 15 different biotopes, viz and ca. 4% from worlds plant, mammals, birds, reptiles, amphibians, fishes and insects diversity, all within an area less than 169.000 hectares 420.000 acres.

Of his research partner and wife, Winifred Hallwachs, Janzen says "We did these things together," and "we are very much together in perceiving things the same things.Since Im the vocal member, its then attributed to me. But I would say these ideas and directions and thoughts and actions are easily fifty-fifty attributable."

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. 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, which, to paraphrase its natural counterpart, ought to be grown as well. ACG integrates complementary processes of experimentation, habitat restoration and cultural development. The techniques used include:

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


3. Honorary distinctions

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 conservations projects in Costa Rica; amongst the 19 prizes and distinctions, the following are the most important:

  • 1993, Award for Improvement of Costa Rican Quality of Life, Universidad de Costa Rica co award with W. Hallwachs.
  • 2011, BBVA Foundation Frontiers of Knowledge Award of Ecology and Conservation Biology for his pioneering work in tropical ecology and his contributions to the conservation of endangered tropical ecosystems throughout the world, drawing on an understanding of plant-animal interactions. Janzen acknowledged the role of his wife and long-term research partner, ecologist Winnie Hallwachs, to the work being recognized.
  • 1991, Founders Council Award of Merit, Field Museum of Natural History
  • 1995, Global Service Award, Society for Conservation Biology
  • 2002, Albert Einstein World Award of Science, Consejo Cultural Mundial, Mexico
  • 1987, Global 500 Roll of Honour, UNEP
  • 1996, Honorary Doctor of Science, University of Minnesota.
  • 2013, Wege Foundation $5 million grant to the Guanacaste Dry Forest Conservation Fund GDFCF, founded in 1997 by Dan Janzen and Winnie Hallwachs.
  • 1989, MacArthur Fellowship
  • 1987, The Berkeley Citation for Distinguished Achievement and Notable Service to the University, University of California, Berkeley
  • 1985, Distinguished Teaching Award, University of Pennsylvania
  • 2014, Blue Planet Prize, from the Asahi Glass Foundation
  • 1994, Silver Medal Award, International Society of Chemical Ecology.
  • 1987, Hijo Ilustre de Guanacaste awarded by the Governor of Guanacaste province
  • 1984, Crafoord Prize: Coevolutionary ecology. Royal Swedish Academy of Sciences
  • 1996, Thomas G. and Louise E. DiMaura Endowed Term Chair, University of Pennsylvania
  • 2006, Winner, National Outdoor Book Awards NOBA, for 100 Caterpillars: Portraits from the Tropical Forests of Costa Rica 2006, Design & Artistic Merit Category.
  • 1975, The Henry Allan Gleason Award, Botanical Society of America
  • 1989, Leidy Award, Philadelphia Academy of Natural Sciences
  • 1992, Member, National Academy of Sciences, USA
  • 1997, Kyoto Prize Basic Sciences Field, Inimori Foundation
  • 2002, Honorary Fellow of the Association for Tropical Biology and Conservation ATBC

4. Publications

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

  • Janzen, D. H. 1986. Guanacaste National Park: tropical ecological and cultural restoration. San Jose, Costa Rica: Editorial Universidad Estatal a Distancia. ISBN 9977-64-316-4.
  • Janzen, Daniel H. editor 1983, Costa Rican Natural History, Chicago: University of Chicago Press, p. 823, ISBN 9780226393346 CS1 maint: extra text: authors list link
  • Janzen, Daniel H. 1985. "Spondias mombin is culturally deprived in megafauna-free forest". Journal of Tropical Ecology. 1 2: 131–155. doi:10.1017/S0266467400000195. JSTOR 2559336.
  • Janzen, Daniel H. September 1966. "Coevolution of Mutualism Between Ants and Acacias in Central America". Evolution. 20 3: 249–275. doi:10.2307/2406628. JSTOR 2406628. PMID 28562970.
  • 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 CS1 maint: multiple names: authors list link CS1 maint: extra text: authors list link

  • tropical rainforests. It was published independently in the early 1970s by Daniel Janzen and Joseph Connell. According to their hypothesis, host - specific herbivores
  • a UNESCO World Heritage Site. The work of Hallwachs and her husband Daniel Janzen at ACG is considered an exemplar of inclusive conservation. Beginning
  • In 1979, the Bokyi population exceeded 190, 000. Julian Caldecott Daniel H Janzen 30 July 2009 Designing Conservation Projects. Cambridge University
  • Communes de la Provincia de Esmereldas Rome: UNFAO, 1969 p. 222 Daniel H Janzen Costa Rican Natural History Chicago: Univ. Chicago Press, 1983
  • base and along the anal margin. The species is named in honour of Daniel H Janzen Miller, James S. Thiaucourt, Paul November 1, 2011 Diversity
  • Dimaura, who have allowed the University of Pennsylvania to support Daniel H Janzen and Winnie Hallwachs full - time in their efforts to facilitate the germination
  • Retrieved 9 September 2014. Paul D. N. Hebert Erin H Penton John M. Burns Daniel H Janzen Winnie Hallwachs 2004 Ten species in one: DNA barcoding
  • Osborne Wilson 1983 G. Ledyard Stebbins 1985 Hampton Carson 1989 Daniel H Janzen 1994 Peter and Rosemary Grant 2006 David B. Wake 2009 Dan Otte
  • Venada www.nic.funet.fi. Retrieved 7 December 2016. Burns, John M. Janzen Daniel H Hallwachs, Winnie Hajibabaei, Mehrdad 2013 DNA Barcodes Reveal