The little red and blue frog is an example of a transexual species that changes its sex over the course of its lifetime. Photo by Justin D. Yeager
Discovering Tropical Diversity
By Ira Rubinoff
The average visitor to Panamá might not be attracted to a site that hosts a hundred species of cockroaches and 41 species of snakes. But Barro Colorado is a mecca for scientists interested in biodiversity.
The island, a field station of the Smithsonian Tropical Research Institute (STRI), is a reserve that reflects Panamá’s special geological history as a strategic land bridge between North and South America. The country in general and Barro Colorado in particular provide a rich laboratory for scientists to examine changes in biodiversity. Understanding the ecology and evolution of the diversity of life on our planet remains a key scientific endeavor of our time. The STRI—using its first Panamanian lowland field station as a base—has expanded its research to the Andean mountains to the Amazon and even the African savannah.
Today, STRI is a platform for long-term research on biodiversity, ecosystems and impacts of environmental change. Global climate systems and life on the planet have always been in flux. It is essential that we provide policy makers with long-term data on the dynamic changes of forests and marine systems around the globe to distinguish the components of global change that can be ascribed to planetary processes from those caused by human activity.
And now these investigations are no longer just the territory of biologists; the current widening and expansion of the Panama Canal and ongoing construction of a third set of locks has provided an opportunity for remarkable cooperation between the Panama Canal Authority and paleontologists. Recognizing that the canal’s expansion required removing the forest that covered many known fossil deposits along the canal’s banks, the Panama Canal Authority has joined with STRI in a comprehensive “salvage paleontology” project. Scientists from STRI, the University of Florida and several institutions in Colombia and Venezuela, with support from the Panama Canal Authority and the United States’ National Science Foundation, have worked in front of the bulldozers to extract the wealth of fossils ranging from the teeth of extinct species of sharks to the remains of extinct horses, turtles, rhinoceroses, manatees, etc. It will require decades and the work of many paleontologists to describe and analyze this fossil abundance.
The seeds for all this research were sown back in 1910, just a few years after Panamanian independence from Colombia. The Smithsonian Institution, a scientific and cultural trust of the United States, was asked to perform a biological inventory of the Panama Canal Zone. It immediately began to organize a group of scientists to do the survey. It wasn’t long before the government of Panamá asked the Secretary of the Smithsonian Institution to extend this survey over all of the provinces of the newly formed Republic. Thus began a long and scientifically fruitful collaboration between these two nations.
Survey results took several years to be published because of their complexity and detail. Many of the scientists involved continued their interest in Panamanian natural history over the longer term, returning frequently for additional fieldwork and collecting expeditions. Then as now, if scientists turned their back on an important study site, it was likely to be converted into a strip mall or, in the case of the Panama Canal Zone, into a government commissary or U.S. military base.
Hence, scientists—including Thomas Barbour, the director of Harvard’s Museum of Comparative Zoology at Harvard—wanted a permanent and protected area. They petitioned the governor of the Canal Zone to set aside a permanent biological reserve where the flora and fauna would be safe for scientific study. Governor James J. Morrow agreed, and set aside the largest island in Gatún Lake, Barro Colorado Island (BCI), formed by the damming of the Chagres River to establish the main fresh-water body facilitating the inter-oceanic passage of marine commerce. This 3,700-acre island became the workshop for much of the research performed in the New World tropics in the early 20th century. As the fauna and flora became better known through research, scientists began to study the behavior and ecology of the island’s biota. These studies attracted more and more scientists from around the world until BCI was sometime referred to as the mecca for biologists.
With World War II underway, the important research on BCI faced a possible threat. The scientific community worried that since the Island’s reserve status depended upon a decree of the governor of the Canal Zone (usually a major general in the U.S. Army Corps of Engineers) some military purpose might seem imperative and the island’s status could be converted into something more appropriate to the war effort. To ensure that the island wasn’t turned into a bombing range or golf course, the U.S. Congress in 1940 created the Canal Zone Biological Area (CZBA) as a separate governmental agency to be administered by a board of directors made up of prominent scientists, including the Secretary of the Smithsonian Institution. The CZBA struggled throughout the war since the Congress argued that the research on biodiversity (a term not yet coined) was not sufficiently relevant to the war effort to warrant any financial appropriations.
THE BIRTH OF THE SMITHSONIAN TROPICAL RESEARCH INSTITUTE
Immediately following World War II, many small government agencies formed during the war were either eliminated if they no longer had a purpose or were incorporated into larger organizations. The CZBA officially became a bureau of the Smithsonian Institution in 1946 under a government reorganization act signed by President Harry Truman. Barro Colorado Island is an enormously diverse tropical habitat: 5 species of primates; 5 species of cats; 6 species of opossums; 74 species of bats; 384 species of birds; 33 species of frogs and toads; 23 species of lizards, 41 species of snakes; more than 400 species of ants including 28 species of army ants; 100 species of cockroaches; between 500-600 species of butterflies, perhaps 2,000 species of moths and tens of thousands of other insects, many not yet described. Moreover, there are some 1500 species of plants for all of these animals to nest in, hide in, feed on, and generally interact in an ever dynamic ecosystem—the details of which generations of scientists have endeavored to understand with increasing precision. In addition, there are unknown thousands of fungi, bacteria and viruses that catalyze the exchange of nutrients, regulate decomposition and generally help the ecosystem function.
Barro Colorado Island is an excellent example of one important type of tropical ecosystem—a lowland seasonal forest. However, tropical biologists are concerned with all the diverse habitats of the world’s tropics. The Smithsonian’s scientists in Panamá began to expand their investigations off the island; to the Atlantic and Pacific coasts and their many archipelagos, to the highlands of Chiriquí Province, the vast, hardly explored forests of Darien; to the Andes of Colombia and Ecuador; to the Amazon of Perú and Brazil; and to the rainforests of Asia, the savannahs of Africa or the highlands of Papua New Guinea. This increased geographic scope prompted the Smithsonian Institution’s Board of Regents to approve a name change in 1966, calling its branch the Smithsonian Tropical Research Institute (STRI) to reflect its broadened research scope, no longer confined to BCI, the Canal Zone or even the Isthmus of Panama.
Of course, the public and the scientific community expect much more of biodiversity than lists of the organisms found in the area. And modern science has provided a much broader understanding of the economic, health, and ecosystem values of much of this diversity. In some cases, we realize that an ecosystem may be dependent upon a “keystone” species—one whose removal may lead to the collapse of many others. A cascading “domino effect” may occur whereby the removal of a key fig tree species may result in the extinction of certain mammals, birds, insects and other organisms dependent upon that single species to sustain them through the food scarcity of the dry season.
Research at STRI helped overturn the conventional wisdom that the tropics are dominated by stable communities of highly co-adapted organisms. Large-scale forest plots, first pioneered on Barro Colorado Island in 1980, allow long-term examination of processes that shape tropical forests. These monitoring plots have now been established at 47 sites in 21 countries, enabling forest scientists to make a census of 4.5 million trees of 8,500 species and for the first time allowing comparisons of both tropical and temperate forests with measurements taken using identical protocols. Data from these plots have resulted in almost 1,000 scientific publications and have been crucial in shaping our ideas about the origins and maintenance of biodiversity.
Progress has also been made in evaluating the “ecosystem services” of a rainforest. The Panama Canal is arguably one of the most important watersheds on this planet with some 5 percent of world commerce dependent upon it. The watershed plays four critical roles: providing the basic supply of fresh water for the canal; that of a sponge, absorbing excess water in the rainy season and releasing it more slowly during the dry season when a scarcity of water could limit the draught requirement of ships passing through the canal; the potable water supply for the port cities of Colón and Panama City; and the generation of hydroelectric power. During the rainy season, the forested watersheds slow runoff, preventing catastrophic canal—threatening floods, erosion and costly sedimentation of the Alajuela and Gatún Lakes.
STRI research has informed the Panama Canal Authority on how to reforest with native species, identifying native species of trees such as those in the genus Clusia which effectively control soil erosion while at the same time using only a small amount of water for their own respiration in comparison to species such as teak (Tectona) or mahogany (Swietenia). As carbon has become a tradable commodity, STRI research has contributed to methodologies for measuring the carbon content of different forest and for assessing whether these values are increasing or decreasing.
STRI investigations have not been limited to documenting the diversity of living plants and animals but also serve to describe the extinct biota. These studies contribute to our understanding of past diversity and the geological and climate changes that have contributed to the shaping of the Western Hemisphere and how these changes affect the rest of the planet in diverse ways.
The rise of the Isthmus of Panamá occurred about 3.5 million years ago, facilitating the migration of South American organisms northward and North American organisms southward. Most South American animal species became extinct; in the North, large groups of mammals such as elephants, camels, horses, rhinos also ceased to exist—a process aided perhaps by the arrival of humans at least 13,000 years ago, who with their stone tools and fire were able to change the complexion of the Western Hemisphere.
The completion of the land bridge had another impact with global consequences. It cut off the warm, westward flowing equatorial current, deflecting it northward, facilitating conditions capable of supporting human habitation of Western Europe. At the same time the Gulf Stream may have moved enough moisture northward to promote glaciations in North America and, in some views, also providing the arid conditions in Africa that possibly contributed to our hominid ancestors descending from trees and becoming biped hunter-gathers leading to modern man. The Isthmus of Panamá changed the world in many ways and continues to do so today.
As mentioned above, paleontologists are working literally in front of the bulldozers to recover the past. Another aspect of STRI’s biodiversity research relates to the shipping from around the world that passes through the canal. This movement often enables exotic species to invade new geographic areas, either as organisms trapped in ballast tanks or as the growth of organisms that constitute the fouling attached to the bottoms of ships and barges.
Concern about the exchange of life between the Atlantic and Pacific peaked in the 1960s when exploration about the use of nuclear devices in constructing harbors and canals led to numerous studies by marine biologists (this author included). The research analyzed the possible consequences of allowing organisms long isolated in one ocean to freely invade another where they were not adapted to prey, predators and oceanic conditions. The question of whether the presence of exotic species in areas where they might not be controlled by their usual limiting predators and/or diseases contributed to the decision not to construct a canal at sea level but rather to maintain the fresh water barrier of Gatún Lake. Now STRI scientists are able to distinguish native and invasive species using molecular genetics technology, eliminating some of the guesswork about whether a new species truly represented a new arrival or was only a previously undiscovered resident.
Biological diversity in Panamá, as in many places, is threatened by over fishing, clearing of forests for agriculture especially cattle rearing, coastal recreation, urban development and pollution in the form of fertilizers and pesticides of all types. The diversity of Panamá’s coral reefs is being affected by runoff from the land, ocean warming, acidification and a series of recently identified diseases, some of whose origins are still unclear to science.
On land, amphibians, especially high-altitude species, are facing serious danger and even extinction because of the spread of a fungal disease. The fungus, Batrachochytrium dendrobatidis, apparently causes electrolyte imbalance and heart stoppage in vulnerable species. STRI is working with Panamanian and North American organizations to get protected populations of frogs and toads into laboratory culture for eventual release back into nature when a means of dealing with the infection is developed.
The Republic of Panamá and especially the National Authority for Natural Resources (ANAM) has used STRI research to decide where to establish protected areas. Our research contributed to establishing the national parks of Soberanía, Bocas del Toro, Campana, Coiba and others. In recent years, STRI—with support from the National Science Foundation, the National Institute of Health, many universities, the private sector and think tanks, has begun to explore the rich biological diversity of these national parks for the first ecologically guided program for bio-prospecting—seeking natural products which may have pharmaceutical properties. The long process of “drug discovery” is proceeding with STRI cooperation in both the marine and terrestrial habitats of Panamá.
Biodiversity is complicated, sometimes poorly understood and even occasionally reviled by people who believe that having seen “one redwood” they have seen them all. It is important that STRI shares the knowledge it has gained about biodiversity with others. Many of our facilities are open to the public and have programs designed for teacher training to integrate with and augment the science curricula of the Ministry of Education of Panamá.
As we look to the future of STRI in Panamá, we see an opportunity to build on the innovations that have emerged from this Institute in the last fifty years. A number of STRI “firsts” in the science and in the tropics make this ambition appear reasonable. We were the first to employ construction cranes to examine the biodiversity of organisms associated with the canopy of forest trees and to study the photosynthetic processes at this difficult to access inter-face between the biosphere and atmosphere. Barro Colorado Island also broke ground in remotely monitoring animal behavior using automated telemetry systems. And our work on cryptic female choice in insects and birds and sex change over the course of the lives of many reef fishes have helped explain the evolutionary significance of sex. These are just a few examples of our innovation, invention and intellectual leadership.
We are now poised to explore the value of becoming a “stand alone” graduate university. As it is, we currently provided hundred of fellowships to students at all levels from more than 40 nations every year. Many students pursue their doctoral thesis work here and even more their post-doctoral studies. It seems less than efficient for students of tropical science to need to spend a year of their graduate work in Chicago, New York or Montreal before beginning their dissertation on research questions that need to be pursued in the tropics. Why not provide the full university experience in a location where the partnership between the Republic of Panamá and the Smithsonian Tropical Research Institute already provides the background, facilities and intellectual experience to effectively train the next generation of tropical scientists?
Ira Rubinoff was Director of the Smithsonian Tropical Research Institute from 1974 until 2008. He is currently at STRI as Director Emeritus and Senior Scientist. He received a Ph.D. from Harvard University in 1964.