Daniel H. Janzen

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Daniel Hunt Janzen (born January 18, 1939, in Milwaukee, Wisconsin<ref name="Interview"/>) 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.

Janzen and his wife Winifred Hallwachs have catalogued the biodiversity of Costa Rica. Through a DNA barcoding initiative, Janzen and geneticist Paul Hebert have registered over 500,000 specimens representing more than 45,000 species, which has led to the identification of cryptic species of near-identical appearance that differ in terms of genetics and ecological niche. Janzen and Hallwachs developed some of the most influential hypotheses in ecology that continue to influence research more than 50 years later.<ref name=":1" /><ref name=":2" />

Janzen and Hallwachs helped to establish the Area de Conservación Guanacaste World Heritage Site, one of the oldest, largest and most successful habitat restoration projects in the world.

Early life and education

Daniel Hunt Janzen was born January 18, 1939, in Milwaukee, Wisconsin.<ref name="Interview">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> His father, Daniel Hugo Janzen,<ref>Template:Cite news</ref> grew up in a Mennonite farming community and served as Director of the United States Fish and Wildlife Service.<ref name="Interview"/> His father and mother, Miss Floyd Clark Foster of Greenville, South Carolina, were married on April 29, 1937.<ref>Template:Cite journal</ref>

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.<ref name="Becher"/>

Career

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.<ref name="Becher">Template:Cite book</ref>

Janzen taught at the University of Kansas (1965–1968), the University of Chicago (1969–1972), and the University of Michigan (1972–1976) before joining the faculty at the University of Pennsylvania.<ref name="BBVA">{{#invoke:citation/CS1|citation |CitationClass=web }}Template:Dead link</ref> There he is the DiMaura Professor of Conservation Biology, and his research and field work in Costa Rica.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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).<ref name="Ciencias">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Área del Conservación de Guanacaste (ACG)

The Área de Conservación de Guanacaste (ACG) is a prominent conservation area in northwestern Costa Rica, encompassing over 163,000 hectares of diverse ecosystems, including tropical dry forests, rainforests, and marine areas. Established in the 1990s, the ACG unifies several national parks, such as Santa Rosa, Guanacaste, Rincón de la Vieja, and Junquillal Bay, into a single administrative entity. This integration aims to protect and restore the region's unique biodiversity and facilitate natural ecosystem regeneration. The ACG is recognized as a UNESCO World Heritage Site, highlighting its global ecological significance and Costa Rica's commitment to environmental conservation.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Dr. Daniel Janzen, recognizing the necessity for a cohesive conservation strategy in Guanacaste, along with his wife, biologist Dr. Winnie Hallwachs, championed the establishment of a contiguous conservation area to facilitate natural ecosystem regeneration.

Their comprehensive strategy encompassed several key initiatives:

  • Restoring Tropical Dry Forests: Acquiring degraded pastures and enabling the recovery of natural vegetation.
  • Integrating Local Communities: Training local residents to serve as park guards, educators, and conservation advocates.
  • Fundraising for Land Purchases: Securing donations and forming partnerships with international organizations to purchase private lands and integrate them into the protected area.

Research

Janzen's 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.<ref name="Becher"/>Template:Rp <ref name="Mitchell"/> In 1967, for example he described the phenological specialization of bee-pollinated species of Bignoniaceae,<ref>Janzen, D. H. 1967. Synchronization of sexual reproduction of trees within the dry season in Central America. Evolution 21: 620-637.</ref> amongst them a "kind of mass flowering", which Alwyn Howard Gentry in his classification of flowering named Type 4 or "big bang" strategy.<ref>Alwyn H. Gentry. Flowering Phenology and Diversity in Tropical Bignoniaceae. Biotropica 6(1): 64-68 1974</ref> Janzen proposed many hypotheses that inspired decades of work by tropical and temperate ecologists (see below).

Miguel Altieri in his textbook Agroecology: The Science of Sustainable Agriculture says: "Janzen's 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".<ref name="Altieri">Template:Cite book</ref><ref>Template:Cite journal</ref>

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.<ref name="Pringle">Template:Cite journal</ref><ref name="Singer"/> They employed the help of local Costa Ricans, converting their farming skills into parataxonomy, a term they coined in the late 1980s.<ref name="Allen" /><ref name=":0">Kazmier, Robin (June 15, 2017). "The Parataxonomist Revolution: How a Group of Rural Costa Ricans Discovered 10,000 New Species". Comparative Media Studies: Science Writing.</ref> As of 2017, some 10,000 new species in the Area de Conservacion Guanacaste have been identified thanks to the efforts of parataxonomists.<ref name=":0" />

Through a DNA barcoding initiative with geneticist Paul Hebert, they have registered over 500,000 specimens representing more than 45,000 species, which has led to the identification of cryptic species of near-identical appearance that differ in terms of genetics and ecological niche.<ref name="Davis">Template:Cite journal</ref><ref name="Halloway">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Hebert">Template:Cite journal</ref> 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).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref name="Wolf2008">Template:Cite magazine</ref>

Influential hypotheses

Janzen is known for proposing "characteristically imaginative and unorthodox" hypotheses.<ref>Template:Cite journal</ref> These hypotheses have received varying degrees of support,<ref>Template:Cite journal</ref> but are notable for having inspired a large and sustained body of research, as evidenced by the extremely high citation rates of many of his papers for decades after they are published.<ref name=":2" />

One of Janzen's most famous ideas (from his most highly cited paper)<ref name=":2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is now known as the Janzen-Connell hypothesis, as Janzen and Joseph Connell independently proposed the idea in 1970-1971. They both suggested that the high diversity of tropical trees was due, in part, to specialist enemies attacking seeds or seedlings that were particularly close to the parent tree or particularly densely clustered, thus preventing any one species from becoming dominant.<ref>Template:Cite journal</ref>

Another influential idea<ref name=":1">Template:Cite journal</ref> comes from Janzen's 1967 paper 'Why mountain passes are higher in the tropics'.<ref>Template:Cite journal</ref> It proposes that tropical mountains are more of a barrier to species dispersal than temperate mountains because tropical species are less able to tolerate changes in temperature with elevation, having evolved and lived in relatively stable climates.

In a 1977 paper 'Why fruits rot, seeds mould, and meat spoils',<ref>Template:Cite journal</ref> Janzen proposed that microbes render food inedible (or at least distasteful) to vertebrates not just as a by product of microbe-microbe competition or accidental waste products, but as an evolutionary strategy to repel vertebrates consumers, who would otherwise eat the food resource and the microbes themselves. Evidence is mixed, and it is hard to test whether compounds evolved to deter other microbes or vertebrates,<ref>Template:Cite news</ref> but the idea has been widely incorporated into studies of vertebrate feeding from humans<ref>Template:Cite journal</ref> to dinosaurs.<ref>Template:Cite journal</ref>

Coevolution of plants and animals

Tropical habitat restoration

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.<ref name="Wilson">Template:Cite book</ref> They have been cleared, burnt and replaced by pastures for cattle raising,<ref name="Burgos">Template:Cite journal</ref> at an ever-faster rate during the last 500 years.<ref name="Wilson"/>

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. Janzen and his wife helped to establish the Area de Conservación Guanacaste World Heritage Site (ACG), one of the oldest, largest and most successful habitat restoration projects in the world. They began with the Parque Nacional Santa Rosa, which included Template:Convert of pasture and relictual neotropical dry forest and Template:Convert of marine habitat.<ref name="Pringle"/> This eventually became the Área de Conservación Guanacaste, located just south of the Costa Rica-Nicaragua border, between the Pacific Ocean and the Cordillera de Tilaran which integrated four different national parks. Together these house at least 15 different biotopes (namely mangroves, dry forest and shrubs; ephemeral, rainy season, and permanent streams; fresh water and littoral swamps; evergreen rainforests and cloud forests, etc.), holding approximately 4% of the world's plant, mammal, bird, reptile, amphibian, fish, and insect diversity, all within an area of less than Template:Convert.<ref name="Area">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is one of the oldest, largest and most successful habitat restoration projects in the world. As of 2019, it consists of Template:Convert.<ref name="Area"/> 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.<ref name="Davis"/>

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, and the proliferation of fire-resistant and unpalatable weeds from the Old World tropics and subtropics.<ref name="Gomiero">Template:Cite journal</ref> One is also faced with the difficulties of changing a culture that coevolved with, profited from, and can become miserable with such a system.<ref name="Costanza">Template:Cite book</ref><ref>Template:Cite journal</ref><ref name="march">Template:Cite journal</ref>

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.<ref name="Allen"/>Template:Rp<ref name="Derroire">Template:Cite book</ref> The techniques used include:

  • Active restoration, artificial dispersal of propagules from plant species native to the Guanacaste habitats<ref name="Derroire"/>Template:Rp
  • Passive restoration by means of fire, anti-poaching and herbivore control<ref name="Derroire"/>Template:Rp
  • Ecological education and sensibilisation<ref name="Allen"/>Template:Rp<ref name="Singer">Template:Cite book</ref><ref name="Cruz">Template:Cite journal</ref><ref name="Kazmier">{{#invoke:citation/CS1|citation

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Personal life

Janzen is married to ecologist Winifred Hallwachs, who is also his frequent research partner. Of Hallwachs, Janzen has said, "We did these things together,"<ref name="Allen"/>Template:Rp and "we are very much together in perceiving things the same things....Since I'm the vocal member, it's then attributed to me. But I would say these ideas and directions and thoughts and actions are easily fifty-fifty attributable."<ref name="Allen"/>Template:Rp

Honorary distinctions

Janzen has been subject to recognition many times in the US, 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. Prizes and distinctions garnered by Janzen include:

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  • 1985, Distinguished Teaching Award, University of Pennsylvania<ref name="Fishman">Template:Cite news</ref>
  • 1987, The Berkeley Citation for Distinguished Achievement and Notable Service to the University,<ref>{{#invoke:citation/CS1|citation

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  • 1996, Thomas G. and Louise E. DiMaura Endowed Term Chair, University of Pennsylvania<ref>{{#invoke:citation/CS1|citation

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  • 2002, Honorary Fellow of the Association for Tropical Biology (and Conservation) (ATBC)<ref>{{#invoke:citation/CS1|citation

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  • 2006, Winner, National Outdoor Book Awards (NOBA), for 100 Caterpillars: Portraits from the Tropical Forests of Costa Rica (2006), Design & Artistic Merit Category.<ref name="NOBA">{{#invoke:citation/CS1|citation

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  • 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.<ref name="Ibol">{{#invoke:citation/CS1|citation

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  • 2013, Wege Foundation $5 million grant to the Guanacaste Dry Forest Conservation Fund (GDFCF), founded in 1997 by Dan Janzen and Winnie Hallwachs.<ref name="WEGE">{{#invoke:citation/CS1|citation

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See also

Publications

The following is a selection of Janzen's publications that are not otherwise listed.

References

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