Paleoecology

by

Alistair Seddon

• LAST REVIEWED: 23 May 2012
• LAST MODIFIED: 23 May 2012
• DOI: 10.1093/obo/9780199830060-0058

Introduction

Paleoecology, the ecology of the past, uses geological and biological evidence from fossil deposits to investigate the past occurrence, distribution, and abundance of different ecological units (species, populations, and communities) on a variety of timescales. Although it can be studied in any period of the Earth’s history, paleoecologists are mainly concerned with investigating past ecosystem dynamics over the Quaternary period (the last 2.58 million years), as vast ice sheets cyclically expanded and contracted from the polar regions in response to small variations in the configurations of the Earth’s orbit. The field is multidisciplinary in nature: researchers combine techniques from paleontology, sedimentology, and geochemistry in order to reconstruct past environmental dynamics and to investigate biotic responses to environmental change. While deep-time paleoecologists use fossils from pre-Quaternary sediments, the majority of paleoecological research is concerned with biotic changes for approximately the last 20,000 years, when the age of sediments can be accurately determined using radiocarbon dating. Therefore, texts relating to Quaternary paleoecology are the major focus of this article. There have been major advances in the discipline of Quaternary paleoecology since the late 19th century, when the early pioneers observed fossilized tree stumps preserved in the peat deposits of northern Europe, thus inferring evidence of past climate change. Today, the use of paleoecological data is divided in two ways: paleoecological reconstructions, a descriptive approach in which paleoecological data are used as a tool to reconstruct past landscapes, ecosystems, and environments; and ecological paleoecology, in which ecological hypotheses are tested in order to understand the mechanisms of the observed changes. Both are characterized by increased sophistication, precision, and accuracy over time. More recently, the Quaternary paleoecological record has been applied to helping solve major issues faced by the accelerated global changes of the twenty-first century. By identifying ecological thresholds and allowing “natural” rates of change to be established, ecological “baselines” can be identified for conservation, while fossil evidence can be used to investigate past analogues of change and to train Earth system models. The new developments in paleoecology ensure that it remains an important, hypothesis-driven science that continues to remain relevant in the present day. The author thanks Ambroise Baker, Rick Battarbee, John Birks, Catherine Downy, Anson Mackay, and Gavin Simpson for their helpful contributions to earlier versions of this article.

General Overviews

Birks 2008 introduces key players in the historical development of the discipline and provides a summary of the basic approaches used in paleoecological science today. This text should serve as a starting point for undergraduates and provides numerous useful references for further reading. A similar summary is provided in Seppä 2009, which assesses the ways in which paleoecological records, extending from years to millions of years, are used to test ecological and biogeographic hypotheses. For a broader understanding of the nature of climatic changes during the Quaternary, Walker and Lowe 2007 summarizes the key advancements in Quaternary science since the 1960s. Although not specifically concerned with biological proxies, this paper provides a good overview of the findings in our understanding of global environmental change during the Quaternary period. Similarly, Dearing, et al. 2006 outlines the ways in which Holocene paleoenvironmental data (c. the last 11,500 years) can be relevant for understanding present-day rates of environmental change. All these texts are useful for undergraduates studying paleoecological science for the first time. In addition, Bennett 1997 is an excellent example of a paleoecological investigation for final-year undergraduates and postgraduate students; this book provides a useful overview of the timescales and drivers of environmental change of interest for paleoecologists, and their impacts on the Earth’s biota. Since paleoecology has close roots in geological analysis, it has been heavily influenced by the concept of uniformitarianism, the principle that “the present is the key to the past.” This has been an important concept in the Earth sciences, and students interested in the key assumptions of uniformitarianism should read Gould 1965. Finally, Jackson and Erwin 2006 is included here as an example of deep-time paleoecological methods, more commonly referred to as “paleobiology” or “paleontology.” This paper demonstrates the types of questions that analysts of fossil records can address with regard to ecological and evolutionary changes over thousands to millions of years.

• Bennett, Keith D. 1997. Evolution and ecology: The pace of life. Cambridge, UK: Cambridge Univ. Press.

  A comprehensive case study on the drivers of environmental change leading into and during the Quaternary period, and the ecological and evolutionary impacts that these environmental shifts can drive. Demonstrates how paleoecological data can lead to a better understanding of evolutionary processes, and questions the importance of gradual evolutionary change for understanding macroevolutionary processes.

• Birks, H. John B. 2008. Paleoecology. In Encyclopedia of ecology. Edited by Sven Erik Jorgensen and Brian D. Fath, 2623–2634. Amsterdam: Elsevier.

  Essential starting point for undergraduates who require a brief overview on the development of paleoecological science since the late 19th century.

• Dearing, John A., Richard W. Battarbee, Richard Dikau, Isabelle Larocque, and Frank Oldfield. 2006. Human–environment interactions: Learning from the past. Regional Environmental Change 6.1–2: 1–16.

  DOI: 10.1007/s10113-005-0011-8

  Demonstrates the ways in which the Holocene environmental record can be used to understand interactions between human and natural systems both in the present and the future.

• Gould, Stephen J. 1965. Is uniformitarianism necessary? American Journal of Science 263.3: 223–228.

  DOI: 10.2475/ajs.263.3.223

  Addresses the assumptions inherent in uniformitarianism. Argues that rates of geological processes have not been constant through time, instead proposing “methodological uniformitarianism,” which assumes that Earth system processes are the same, but that they can occur at different rates at different times.

• Jackson, Jeremy B. C., and Douglas H. Erwin. 2006. What can we learn about ecology and evolution from the fossil record? Trends in Ecology & Evolution 21.6: 322–328.

  DOI: 10.1016/j.tree.2006.03.017

  An example of deep-time paleoecology, more commonly referred to as paleobiology or paleontology. Summarizes the key lessons we have learned about ecological and evolutionary processes from the fossil record, by focusing on ecological and evolutionary changes over thousands to millions of years.

• Seppä, Heikki. 2009. Palaeoecology. eLS. (15 September).

  DOI: 10.1002/9780470015902.a0003232

  Shows how paleoecological records, extending from years to millions of years, can be used to test ecological and biogeographical hypotheses. Summarizes how paleoecology has been used to investigate (1) rates of speciation and extinction, (2) biome shifts and ecosystem development, and (3) adaptation, migration, and population change. Available online for purchase or by subscription.

• Walker, Mike J. C., and John J. Lowe. 2007. Quaternary science 2007: A 50-year retrospective. Journal of the Geological Society 164.6: 1073–1092.

  DOI: 10.1144/0016-76492006-195

  Reviews fifty years of progress in our attempts to understand the Quaternary Earth system. Using geochemical, geophysical, and biological evidence, provides a broad perspective on the nature of Quaternary environmental variability and discusses future directions.