Preliminary report of NSF-sponsored, Paleontological Society workshop "Geobiology and the Earth Sciences in the Next Decade", March 6-9, 1999, Smithsonian Institution, Washington, D.C.
The last decade has seen the remarkable development of a new breadth and volume of empirical evidence, conceptual approaches, analytic tools, and technologies relevant to quantifying and modeling rates and patterns of changes in the earth-life system. The geologic record provides dramatic evidence that the earth-life system behaves in a dynamic, non-linear fashion and that the present state fails to include the full range of past or potential states. Thus, we must use this unique archive of information and natural experiments on how the earth-life system operates, assessing how prior events and past states have shaped the present condition, in order to predict future conditions.
Research in paleontology has been transformed by advances in statistical approaches, computer modeling, and the development of global and regional databases. Increased rigor has resulted from application of methods for accommodating known biases in sampling, for testing the significance of observed patterns, and for using empirical patterns to both generate and test hypotheses. These advances in paleontology are now being coupled with those in related geoscience and life science disciplines. These disciplinary linkages set the stage for significant advances in understanding the evolution of biocomplexity, the dynamics of life on earth, and the diverse ways in which life has driven, and been driven by, changes in the earth's oceans, atmosphere, and lithosphere over evolutionary time.
Four related research themes promise major advances in understanding and modeling the range of past states, and the rates and mechanisms of change in the earth-life system.
1. What rules govern biodiversity dynamics, and do they apply at all temporal and spatial scales?
Through geologic time, global biodiversity (measured as number of taxa, as range of body forms, and as ecological variety) has shown an overall trend of net increase. However, this general trend has not been smooth: diversification has occurred episodically, has been interrupted by extinction events, and has had (in the oceans) at least one prolonged episode of little change. This complex trajectory was shaped by an interplay of physical and biological processes. A well-concerted and broad-based effort is needed now to test hypotheses on driving mechanisms - which will guide the next generation of sampling efforts - and to develop the next generation of models that treat dynamics in terms of underlying components such as origination and extinction rates over a spectrum of spatial and temporal scales.
2. Why are major evolutionary innovations unevenly distributed in space and time?
One of the most striking patterns emerging from paleontological analyses is that biological innovations - the breakthroughs that open new ecological opportunities and evolutionary pathways - do not arise randomly in space and time. Evolutionary innovations are associated with episodes of taxonomic diversification (the multiplication of species and higher groups) or the expansion of lineages into new habitats or lifestyles. Some of these innovations - such as photosynthesis, animal body plans, land plants, and mineralized skeletons in marine microplankton - undoubtedly drove changes in conditions on the earth's surface.
Key research issues concern the environmental and biotic controls on episodes of innovation, the geographic distribution of innovation, and the impact of innovations on both ecosystems and biogeochemical processes.
3. How does the biosphere respond to environmental perturbations at regional and global scales?
Rapid climatic changes, extra-terrestrial impacts, shifts in ocean chemistry, biological migrations, and other perturbations have repeatedly influenced the history of life, perhaps most dramatically during mass extinctions, but during normal times as well. These environmental perturbations and the biotic responses are natural experiments that provide the foundation for a research agenda that includes calibrating biotic responses to different types and magnitudes of disturbance across a range of temporal and spatial scales. Such a comparative, quantitative approach is needed to discover general, predictive rules for biosphere behavior. A variety of rigorous, empirically derived models, in which extinction rates and origination rates are critical factors, have been developed to account for these patterns. These models now need to be expanded and tested to explore the roles of geographic distribution, environmental conditions, initial states, and other factors in determining biotic responses to different kinds of perturbation. Our ability to sample the fossil record with ever-increasing spatial and temporal acuity enables us to test and resolve these issues.
4. How have biological systems influenced the physical and chemical nature of the earth's surface, and how has biogeochemical cycling changed through time?
The sedimentary record reveals a succession of worlds of radically different character, ranging from the exclusively microbial and oxygen-poor Archean to the highly heterogeneous modern system, that includes a huge diversity of morphologically and behaviorally complex multicellular organisms. These changes are evident in the composition and preservational nature of the fossil record, and the diversity, abundance and temporal distribution of sediment types and geochemical signatures. The broad coincidence of major biological, sedimentary, and geochemical transitions throughout earth history indicates that strong links exist between the biosphere and the earth's surface systems. Research efforts in the next decade will identify time intervals when significant changes took place in biological materials and in biogeochemical cycling, the short-term dynamics of these changes, how steady-states are maintained, and the roles of biological innovations in generating patterns and rates of such cycling. Given the importance of microbial processes, studies of molecular biomarkers and of isotopic records will be of particular value.
Significant progress on these themes requires a balance of efforts, ranging from traditional individual-investigator research, through collaborative and interdisciplinary projects, and including a major new initiative in data compilation, dissemination, and analysis. Proposals from individuals and groups of scientists will continue to be highly productive vehicles for supporting research and training in paleontology. Such "core"support must be strengthened. The increased computational and analytical sophistication of paleontological research requires funding levels significantly higher than in the past, for both individuals and groups.
In addition, the time is right for the construction of a central, multidimensional database that integrates global paleontologic data with those on paleogeography, geochemistry, paleoenvironment, geochronology, and a wealth of other aspects of earth history. The linkage of earth history data in a relational format will provide a database of unprecedented versatility, power, and accessibility. This database is essential to test hypotheses of linkages between different components of the earth-life system, and the origins and evolution of biocomplexity.
The Earth History Database Initiative will be a decade-long effort that will require its own physical and virtual infrastructure. Existing databases will be integrated, protocols for adding new data will be established, and focused efforts on collecting new data central to answering the questions raised above will be supported. An Earth History Database is central to maximizing efforts, facilitating research, disseminating results, and providing a linkage between research and education. The power of the internet will make the record of earth history available in every classroom.
Richard K. Bambach, Virginia Tech
Peter R. Crane, Field Museum of Natural History
Steven L. D'Hondt, University of Rhode Island
William A. DiMichele, Smithsonian Institution
Douglas H. Erwin, Smithsonian Institution
Karl W. Flessa, University of Arizona
John J. Flynn, Field Museum of Natural History
Robert A. Gastaldo, Auburn University
Steven M. Holland, University of Georgia
David Jablonski, University of Chicago
Jeremy B. C. Jackson, Scripps Institution of Oceanography
Roger L. Kaesler, University of Kansas
Patricia H. Kelley, University of North Carolina, Wilmington
Susan M. Kidwell, University of Chicago
Paul L. Koch, University of California, Santa Cruz
Timothy W. Lyons, University of Missouri, Columbia
Christopher G. Maples, Indiana University
Charles R. Marshall, University of California, Los Angeles
Arnold I. Miller, University of Cincinnati
Barun K. Sen Gupta, Louisiana State University
Dale A. Springer, Bloomsburg University
Steven M. Stanley, Johns Hopkins University