Conservation Paleobiology

Science and Practice

Gregory P. Dietl, Karl W. Flessa, Gregory P. Dietl, Karl W. Flessa

• Publisher: University of Chicago Press
• Year: 2017
• ISBN:
  9780226506869
• Topic: Scienze biologiche
• Subtopic: Scienza generale

In conservation, perhaps no better example exists of the past informing the present than the return of the California condor to the Vermilion Cliffs of Arizona. Extinct in the region for nearly one hundred years, condors were successfully reintroduced starting in the 1990s in an effort informed by the fossil record—condor skeletal remains had been found in the area's late-Pleistocene cave deposits. The potential benefits of applying such data to conservation initiatives are unquestionably great, yet integrating the relevant disciplines has proven challenging. Conservation Paleobiology gathers a remarkable array of scientists—from Jeremy B. C. Jackson to Geerat J. Vermeij—to provide an authoritative overview of how paleobiology can inform both the management of threatened species and larger conservation decisions.Studying endangered species is difficult. They are by definition rare, some exist only in captivity, and for those still in their native habitats any experimentation can potentially have a negative effect on survival. Moreover, a lack of long-term data makes it challenging to anticipate biotic responses to environmental conditions that are outside of our immediate experience. But in the fossil and prefossil records—from natural accumulations such as reefs, shell beds, and caves to human-made deposits like kitchen middens and archaeological sites—enlightening parallels to the Anthropocene can be found that might serve as a primer for present-day predicaments. Offering both deep-time and near-time perspectives and exploring a range of ecological and evolutionary dynamics and taxa from terrestrial as well as aquatic habitats, Conservation Paleobiology is a sterling demonstration of how the past can be used to manage for the future, giving new hope for the creation and implementation of successful conservation programs.

SECTION ONE

Conservation Paleobiology in Near Time

THE EIGHT chapters in this section explore the approaches of conservation paleobiology in the parts of the geohistorical record where the species and habitats are most like those of today. We use the arbitrary dividing line of approximately 2.5 million years: shortly before the onset of the climatic fluctuations that define the Pleistocene. Continents and oceans were largely in their present locations; sea level, though in fluctuation during the glacial cycles, was for the most part similar to what it is today; and human activities began to shape the earth’s surface and climate. This time interval includes the Pleistocene, the Holocene, and what has come to be called, informally, the Anthropocene—the interval of geologic time in which human activities exert a significant effect on the Earth (Zalasiewicz et al., 2011; Lewis and Maslin, 2015).

The near-time approach takes great advantage of the wealth and quality of geohistorical data available from accumulating sediments, biotic remains, ice cores, tree rings, and archaeological sites, among other archives (see NRC, 2005; Dietl and Flessa, 2011). Many species alive today can be traced back through near time, and although the near-time record contains extinct species, their biotic roles and relationships are relatively easy to decipher. Near time also has the great advantage of the availability of high-precision dating techniques such as dendrochronology, radiocarbon, amino acid racemization, and uranium-thorium dating. Knowing the age of a specimen or its enclosing sediment is vital to understanding the times and rates of environmental and biotic change.

The geohistorical record of near time is rich and diverse. Michał Kowalewski (Chapter 1) and Susan Kidwell (Chapter 7) discuss the marine environment’s abundance of shelled invertebrates. The terrestrial realm also yields abundant information, from the vertebrate remains in caves, packrat middens and raptor accumulations (Hadly and Barnosky, Chapter 3), or archaeological sites (Jackson and McClenachan, Chapter 5; Koch, Fox-Dobbs, and Newsome, Chapter 6) to the plant remains represented by pollen, tree rings, and macrofossils (Jackson, Gray, and Shuman, Chapter 4). The sedimentary record of lakes (Smol, Chapter 2) has long been a rich source of information on environmental and biotic change in near time. Indeed, the paleolimnological record of the effects of acid rain is certainly one of conservation paleobiology’s biggest success stories (see also Smol, 2008; Blais et al., 2015). Even the aerial realm is available for study, as illustrated by the case study of diets in California condors (Koch, Fox-Dobbs, and Newsome, Chapter 6).

Fossils and other organic remains are—or contain—proxy indicators. They “stand in” to indicate the presence, abundance, and distribution of species and the time during which they accumulated, their biotic interactions, and the environments in which they lived. Dead remains are, under the right circumstances, excellent proxies for the original live community’s composition and relative abundance (Kidwell, Chapter 7; see also Kidwell, 2013), changing environmental conditions (Kowalewski, Chapter 1; Smol, Chapter 2; Hadly and Barnosky, Chapter 3; Jackson, Gray, and Shuman, Chapter 4; Lyons and Wagner, Chapter 8), and an organism’s life history and behavior (Kowalewski, Chapter 1; Koch, Fox-Dobbs, and Newsome, Chapter 6). Biotic interactions and preservational processes can also leave their marks on the skeletal remains of organisms (Kowalewski, Chapter 1). And, even genetic variability can be tracked through time as ancient DNA becomes more easily acquired and analyzed (Hadly and Barnosky, Chapter 3).

Tools for conservation paleobiologists continue to be developed. Some are well-established and are in wide use as proxy indicators (see above). Others are new and are, as yet, not in wide use. Kidwell (Chapter 7) devises several measures of the difference between members of the living molluscan community and their adjacent remains. These metrics for mismatch may be useful proxies for not only the degree of impact, but also its cause. S. Kathleen Lyons and Peter Wagner (Chapter 8) borrow macroecology’s approaches for the analysis of geographic ranges, body size distributions, diversity, and relative abundance to argue for their use in conservation biology.

The near-time fossil record abounds with examples of past biotic responses to environmental—including climatic—change. Some environmental change can be attributed to direct human impact (examples in Smol, Chapter 2; Jackson, Gray, and Shuman, Chapter 4; Jackson and McClenachan, Chapter 5; Koch, Fox-Dobbs, and Newsome, Chapter 6; Kidwell, Chapter 7), whereas other changes may have resulted from more natural disturbances, including climate change (examples in Smol, Chapter 2; Hadly and Barnosky, Chapter 3; Jackson, Gray, and Shuman, Chapter 4). Indeed, the ecological dynamics of the past provide an opportunity to use the temporal perspective to develop a predictive community ecology (Jackson, Gray, and Shuman, Chapter 4—see also Jackson and Blois, 2015).

REFERENCES

BLAIS, J. M., M. ROSEN, AND J. P. SMOL. 2015. Environmental Contaminants: Using Natural Archives to Track Sources and Long-term Trends of Pollution. Springer, Dordrecht, 509 p.

DIETL, G. P., AND K. W. FLESSA. 2011. Conservation paleobiology: Putting the dead to work. Trends in Ecology and Evolution, 26:30-37.

JACKSON, S. T., AND J. L. BLOIS. 2015. Community ecology in a changing environment: Perspectives from the Quaternary. Proceedings of the National Academy of Sciences of the United States of America, 112:4915-4921.

KIDWELL, S. M. 2013. Time-averaging and fidelity of modern death assemblages: Building a taphonomic foundation for conservation palaeobiology. Palaeontology, 56:487-522.

LEWIS, S. L., AND M. A. MASLIN. 2015. Defining the Anthropocene. Nature, 519:171-180.

NRC (NATIONAL RESEARCH COUNCIL) 2005. The Geological Record of Ecological Dynamics: Understanding the Biotic Effects of Future Environmental Change. The National Academies Press, Washington, D.C., 200 p.

SMOL, J. P. 2008. Pollution of Lakes and Rivers: A Paleoenvironmental Perspective—2nd Edition. Blackwell Publishing, Oxford, 383 p.

ZALASIEWICZ, J., M. WILLIAMS, A. HAYWOOD, AND M. ELLIS. 2011. The Anthropocene: A new epoch of geological time? Philosophical Transactions of the Royal Society London A, 369:835-841.

CHAPTER ONE

THE YOUNGEST FOSSIL RECORD AND CONSERVATION BIOLOGY: HOLOCENE SHELLS AS ECO-ENVIRONMENTAL RECORDERS*

MICHAŁ KOWALEWSKI

Department of Geosciences, Virginia Tech, Blacksburg, VA 24061 USA

. . .

ABSTRACT.—This chapter reviews eco-environmental information that can be extracted from the youngest (surficial) fossil record. The main focus of this review are shell-producing macro-invertebrates, which are abundant at (or near) the sediment surface in many aquatic and terrestrial habitats. As demonstrated by geochronologic and sclerochronologic analyses, such Holocene shell accumulations provide direct, often continuous, records of the most recent centuries and millennia. They offer us a broad spectrum of data, including multiple taxonomic, ecologic, taphonomic, geochronologic, and geochemical parameters that can inform us about the recent history of organisms, communities, ecosystems, and environments. Eco-environmental analyses of shells and other bio-remains provide us thus with a long-term historical perspective; a quantitative baseline for understanding pre-industrial ecosystems, evaluating anthropogenic changes, and assessing restoration efforts. This research strategy, sometimes referred to as “conservation paleobiology,” is often based on dead remains only, and consequently, represents a biologically non-invasive approach to conservation issues. The recently dead—the youngest fossil record of environmental and ecological processes at local, regional, and global scales—can help us to protect the living and should allow us to manage the future of our biosphere more effectively.

. . .

INTRODUCTION

SKELETAL REMAINS of dead organisms are copious in many modern environments: trillions of mollusk shells contour ocean shorelines, coastal dunes are streaked with dense layers of land snail conchs, and countless mussel valves litter streams and rivers. Even dolphin bones—a valuable collector’s item and a non-exportable national commodity—may occur in large numbers in more remote areas (e.g., Liebig et al., 2003) yet undiscovered by beachcombers.

A few examples of surficial accumulations highlighted here on Figure 1 illustrate their exceptional qualities. Among others, these accumulations represent biomineralized remains that are easy to access and do not require expensive sampling machinery (Fig. 1.1, 1.2, 1.4, 1.5, and 1.6). Also, they often provide us with copious quantities of specimens that can be sampled from a single spot (e.g., Fig. 1.2, 1.3, 1.6, and 1.7), and the material is typically preserved exceedingly well; for example, articulated skeletons of vertebrates (Fig. 1.1) or ligament-preserving shells of freshwater mussels (Fig. 1.4) are not uncommon. Finally, these accumulations can be found in a broad spectrum of environmental and depositional settings—from eolian dunes (Fig. 1.5 and 1.6), through river banks (Fig. 1.4), down to various marine habitats, from supratidal mud flats (Fig. 1.1) to open-shelf subtidal seafloors (Fig. 1.7).

To be sure, the wanton abundance of bioskeletal remains has been appreciated since the dawn of science. Starting with Aristotle and da Vinci, biologists and geologists have paid continuing attention to those surficial graveyards. However, only recently, have we begun to appreciate in full the wealth of historical data contained within shells, tests, bones, and other bio-remains scattered on the surface of our planet. This is for two reasons. First, geochronologic and sclerochronologic efforts of the last decades have demonstrated, repeatedly, that the youngest fossils yield continuous, multi-centennial to multi-millennia records of the most recent geological past (e.g., Flessa et al., 1993; Lazareth et al., 2000; Kowalewski et al., 2000; Carroll et al., 2003; Kidwell et al., 2005; Schöne et al., 2005; Kosnik et al., 2007; Yanes et al., 2007). Second, rapid advances in analytical instrumentation have provided us with increasingly diverse, sophisticated, and affordable techniques for dating, analyzing, and interpreting bio-remains left behind by dead organisms (e.g., Dettman and Lohmann, 1995; Kaufman and Manley, 1998; Riciputi et al., 1998; Lazareth et al., 2000; Rodland et al., 2003; Fiebig et al., 2005; Carroll et al., 2006; Fox et al., 2007; Schiffbauer and Xiao, in press). These and related analytical and conceptual advancements make it now possible to use the dead to help the living. That is, skeletal remains offer a quantifiable reference baseline that can help us to understand the living communities, assess the efficacy of restoration efforts, and, ultimately, protect their future. Just as important, this “Conservation Paleobiology” approach—as some refer to it nowadays (e.g., Flessa, 2002)—has a virtue of being partly or completely non-invasive. This is because conservation paleobiology involves sampling efforts that often do not require killing, or even disturbing notably, living biota.

FIGURE 1.—Copious skeletal remains left behind by various organisms found in a wide spectrum of present-day depositional environments; 1, An articulated skeleton of a dolphin on the surface of macrotidal flats of the Lower Colorado River Delta, Mexico. Note also abundant mollusk shells on the surface; 2, Multiple beach ridges made nearly exclusively of disarticulated valves of the bivalve mollusk Mulinia coloradoensis (the Lower Colorado River Delta); 3, A close-up of one of the beach ridges; 4, An articulated shell of a freshwater mussel protruding from a river bank (North Fork Holston River, SW Virginia); 5, Abundant shells of terrestrial snails in a Late Quaternary paleosol, Furteventura Island, Canary Islands; 6, A layer made nearly exclusively of shells of terrestrial snails embedded within a late Quaternary dune, Furteventura Island, Canary Islands; 7, Calcitic shells of the brachiopod Bouchardia rosea dredged from the modern surface of the southern Brazilian Shelf. Photographs courtesy of, and copyrighted to, Karl Flessa, University of Arizona (Fig. 1.1-1.3); Claudio de Francesco (University of La Plata) and John W. Huntley (University of Kentucky) (Fig. 1.4); Yurena Yanes (Southern Methodist University and University of Granada) (Fig. 1.5-1.6); and Marcello G. Simões (Sao Paulo State University) (Fig. 1.7).

Here, I review briefly eco-environmental information that can be extracted from the youngest (surficial) fossil record, with particular focus on shell-producing macro-invertebrates, although other types of macroscopic remains (bones, plants, etc.) will be discussed briefly when relevant. However, micropaleontological approaches to conservation paleobiology (subfossil pollen, test of plankton, etc.) are not discussed in this chapter. In addition, multiple case studies will be used to illustrate ways in which skeletal remains can be employed to augment our understanding of eco-environmental changes over centennial-to-millennial time scales. The main goal here is to highlight the unique historical potential of the data that can be provided by the youngest fossil record (e.g., Kowalewski et al., 2000; Jackson et al., 2001; Brown et al., 2005; Kidwell, 2007). After all, the historical perspective that reaches back in time far beyond the industrial revolution is necessary for the realistic assessment and effective mitigation of widespread anthropogenic changes occurring on our planet today (see especially Jackson et al., 2001; Pandolfiet al., 2003; Flessa et al., 2005; Flessa and Jackson, 2005).

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