Enhanced: Biosphere 2 and Biodiversity--The Lessons So Far

Joel E. Cohen, David Tilman

J. E. Cohen [HN17], [HN18] is at the Rockefeller University, [HN19] New York, NY 10021-6399 USA, and Columbia University, New York, NY 10027, USA. E-mail: cohen@rockvax.rockefeller.edu D. Tilman [HN20]is at the University of Minnesota, St. Paul, MN 55108, USA. E-mail: tilman@swan.lter.umn.edu

On 1 January 1996 (1), Columbia University took over scientific management of Biosphere 2, a 3.15-acre closed ecosystem in Oracle, Arizona, containing soil, air, water, plants, and animals. [HN1], [HN2]Since then, the facility has been seeking suggestions for its future research mission from a broad range of scientists. In September, Columbia's Wallace Broecker, Biosphere 2's new chief scientist, convened a committee of ecologists, plant physiologists, and population geneticists to propose possible biodiversity experiments at Biosphere 2 (2). [HN3], [HN4] These have yet to be evaluated, in part because the new director of Biosphere 2, William C. Harris, has just moved to Columbia from the National Science Foundation. [HN5], [HN6], [HN7] Nevertheless, the committee on biodiversity experiments was struck by some fundamental lessons already learned from Biosphere 2.

No existing closed-environment facilities for ecological research approaches the size and sophistication of Biosphere 2: the original airtight footprint covered 13,000 m² and enclosed 204,000 m³. Despite the enormous resources invested in the original design and construction (estimated at roughly $200 million from 1984 to 1991) and despite a multimillion-dollar operating budget, it proved impossible to create a materially closed system that could support eight human beings with adequate food, water, and air for 2 years. The management of Biosphere 2 encountered numerous unexpected problems and surprises, even though almost unlimited energy and technology were available to support Biosphere 2 from the outside. Isolating small pieces of large biomes and juxtaposing them in an artificial enclosure changed their functioning and interactions rather than creating a small working Earth, as originally intended.

The staff of Biosphere 2, and several reports (3, 4, 5), revealed to the committee numerous examples of surprises that had been encountered since the facility began its first "mission," the widely publicized enclosure of eight Biospherians from 1991 to 1993. By January 1993, 1.4 years after material closure of Biosphere 2, the oxygen concentration in the closed atmosphere fell from 21% to about 14% (see figure). This oxygen level, ordinarily found at an elevation of 17,500 feet, was barely sufficient to keep the Biospherians functioning. Carbon dioxide levels skyrocketed, with large daily and seasonal oscillations. Subsequent analyses discovered that microbial degradation of carbon in the highly fertile soils (needed for food production) consumed the atmospheric oxygen, producing carbon dioxide. Although no one knew it at the time, some of the carbon dioxide combined with the calcium in the concrete used to construct Biosphere 2 to produce calcium carbonate (4). The original atmospheric oxygen, in effect, became locked up in the walls of the structure. In early 1993, before the end of the first 24-month "mission," oxygen was added to Biosphere 2's atmosphere from outside. Another atmospheric problem was also unanticipated. The N₂O concentration of the air rose to 79 parts per million after 3 years of closure. At that level, N₂O may reduce vitamin B₁₂ synthesis to a level that can impair or damage the brain. These and other such unforeseen problems made the biogeochemical regulation of a closed atmosphere a delicate problem.

Vines originally introduced as a carbon dioxide sink (such as morning glory, Ipomoea aff. hederacea) proved to be exceptionally aggressive. The vines required a great deal of hand weeding, which was not entirely successful, to prevent them from overrunning other plants, including food plants. The trunks and branches of large trees became brittle and prone to catastrophic and dangerous collapses. Although some species were expected to go extinct, particularly among the plants, the extremely high fraction of species extinctions (for example, 19 of 25 vertebrate species) was unanticipated (3). All pollinators went extinct. Consequently, the majority of the plant species, which depend on insect or vertebrate pollinators for reproduction, had no future beyond the lifetime of the individuals already present. The majority of the introduced insects went extinct, leaving crazy ants (Paratrechina longicornus) running everywhere, together with scattered cockroaches and katydids. Despite the relatively small size of the Biosphere 2 ocean compared to the land areas, extinction rates in the ocean appeared to be lower than those on land. Air temperatures in the upper reaches of the glass structure were far higher than anticipated, while light levels were significantly lower. Areas designed to be deserts initially became chaparral or grasslands because of a failure to adjust the rainfall to reduced evaporative demand. Water systems became loaded with nutrients, polluting aquatic habitats. Nutrients had to be removed from the water by passage over plates on which algal mats grew. The algal mats were then harvested manually, dried, and stored within the enclosure. Water chemistry management made it necessary to separate a planned brackish estuary from the ocean.

These surprises left the committee with the impression that Biospherians, despite annual energy inputs costing about $1 million (5), had to make enormous, often heroic, personal efforts to maintain ecosystem services that most people take for granted in natural ecosystems. Even these efforts did not suffice to keep the closed system safe for humans or viable for many nonhuman species. Some of the surprises might, in principle, have been foreseen through better linkages with the research community of plant physiologists and ecologists. But several visiting ecologists doubted that a viable closed habitat to support human life could have been assured, even had the best ecological knowledge of the time been brought to bear.

The major retrospective conclusion that can be drawn is simple. At present there is no demonstrated alternative to maintaining the viability of Earth. No one yet knows how to engineer systems that provide humans with the life-supporting services that natural ecosystems produce for free (5). Dismembering major biomes into small pieces, a consequence of widespread human activities, must be regarded with caution. Despite its mysteries and hazards, Earth remains the only known home that can sustain life.

There may be a partial analogy between the initial problems of Biosphere 2 and the early, well-publicized flaws of the Hubble Space Telescope. Just as the Hubble telescope's initial images, although fuzzy, produced insights for astronomers, the initial work in Biosphere 2 has already provided insights for ecologists--and perhaps an important lesson for humanity. Now that the Hubble telescope has been improved, it is a major instrument with the potential for observations never possible before. Similarly, research in a retooled Biosphere 2 may well contribute exciting insights into the task of maintaining the viability of Biosphere 1--the Earth.

References and Notes

1. L. Wolfgang, Science 270, 1111 (1995)[Medline]; C. Macilwain, Nature 380, 275 (1996).[Medline]
2. Committee members: H. A. Mooney, J. A. Berry, J. E. Cohen, R. Dirzo, C. B. Field, L. Graumlich, D. Melnick, S. Naeem, O. E. Sala, and D. Tilman. [HN8], [HN9], [HN10], [HN11], [HN12], [HN13], [HN14], [HN15], [HN16]
3. T. Burgess, B. V. D. Marino, J. Joyce, Biodiversity Working Group Summary, internal report of the Biosphere 2 Science and Research Department (11 to 12 August 1995).
4. J. P. Severinghaus et al., Eos 75, 33 (1994); W. S. Broecker, GSA Today 6, 1 (1996).
5. W. F. Dempster, Tech. Pap. Ser. 932290 (Society of Automotive Engineers, Warrendale, PA, 1993); E. Odum, Nature 382, 18 (1996).[Medline]

HyperNotes
Related Resources on the World Wide Web

The California State University Biological Web Server (CSUBIOWEB), housed at California State University Stanislaus, provides a searchable list of Web sites in biological sciences. A brief description of each site is included with a link to the site.

The World Wide Web Virtual Library: Biosciences , maintained by Keith Robison at Harvard University Biological Laboratories, is a comprehensive list of biology resources. The list is arranged by subject area. It is a part of the World Wide Web Virtual Library distributed catalog project, covering a wide range of subjects.

The Center for Conservation Biology Network is a series of integrated information servers that provide information about conservation biology issues, programs, and opportunities. The site includes the World Wide Web Virtual Library: Biodiversity, Ecology, and the Environment. The virtual library provides links to hundreds of documents on global sustainability resources and information on endangered animals and plants.

The Environmental Resources Information Network, located in the Federal Department of the Environment, Sport and Territories of Australia, maintains Australian Environment On-line. This page provides categorized and annotated lists of Web sites related to the environment and biodiversity in Australia and around the world.

The Biodiversity and Ecosystems NEtwork, BENE, is designed to foster enhanced communications and collaborations among those interested in biodiversity conservation and ecosystem protection, restoration, and management. It includes a categorized list of links to Web sites related to biodiversity.

The Biodiversity and Biological Collections Web Server at the University of Kansas Natural History Museum is devoted to information of interest to systematists and other biologists who study biodiversity and the environment. Within these pages you will find information about specimens in biological collections, taxonomic authority files, directories of biologists, reports by various standards bodies, access to on-line journals, and an extensive list of links to other Web sites.

The United States Environmental Protection Agency provides resources for concerned citizens, students and teachers, business and industry, and researchers and scientists on environmental issues and sustainable human activity.

The World Conservation Monitoring Centre specializes in the location and management of information on the conservation and sustainable use of the world's living resources. WCMC's pages will guide you to global data on biodiversity and information relating to WCMC's activities in this field. The Web site provides access to conservation databases, data, maps and statistics on the forests, coasts, species, and protected areas. The pages include an extensive list of related Web sites.

Sustainable Development Dimensions, A service of the Sustainable Development Department of the Food and Agriculture Organization (FAO) of the United Nations, provides a variety of information resources on sustainable agriculture and development. These resources include reviews of publications on sustainable development, descriptions of activities and programs of the Food and Agriculture Organization, the full text of selected FAO reports, and FAO press releases.

Progress and its Sustainability, a series of Web pages maintained by John McCarthy at Stanford University, presents one view on the sustainability of human material progress.

Information Sources for Sustainable Development, maintained by the International Institute for Sustainable Development (IISD) in Canada, provides a categorized list of information resources for sustainable development. It includes an extensive list of links to related Web sites and the full text of the Youth Sourcebook on Sustainable Development.

The Sustainable Development Resources database contains information on local, national and international organizations and government agencies currently active in the development of sustainable technologies and methods. The database can be searched by topic or geographically.

1. The Biosphere 2 Center Web Site includes a description of the facility, information on faculty and educational programs, and press releases from Biosphere 2, as well as a Sensor Search engine which will retrieve and graph selected data from the hundreds of sensors running inside the project.
2. Columbia University
3. Wallace S. Broecker
4. Wallace S. Broecker's receipt of the National Medal of Science was announced in the Columbia University Record on 6 September1996.
5. Harold A. Mooney
6. Stanford University
7. National Science Foundation
8. Joseph A. Berry
9. Carnegie Institution of Washington Plant Biology Department
10. Chris B. Field
11. Lisa J. Graumlich
12. University of Arizona
13. Don J. Melnick
14. Shahid Naeem
15. University of Minnesota
16. Universidad de Buenos Aires
17. Joel E. Cohen
18. Joel E. Cohen is the author of Maximum Occupancy, an essay published in American Demographics.
19. Rockefeller University
20. G. David Tilman