Species Extinctions

by

Thomas Brooks

• LAST REVIEWED: 10 November 2022
• LAST MODIFIED: 26 August 2013
• DOI: 10.1093/obo/9780199830060-0108

Introduction

The ecology of species extinctions is a topic that cuts through time to the earliest emergence of life on Earth, across space to the planet’s most remote corners, and over taxonomy from the world’s largest animals to teeming invertebrate diversity. Although extinction as a phenomenon has been recognized for centuries (above all, with awareness of dinosaur fossils), most characteristics of extinctions have been realized only since the early 1970s. Above all, these characteristics include selectivity, in at least three forms. Selectivity over time implies that most extinctions occur during discrete periods, referred to as mass extinctions. Five mass extinctions (Late Ordovician, Late Devonian, Late Permian, Late Triassic, and, most recently, end-Cretaceous) occurred through Earth’s geological history, of which the latter, sixty-five million years ago, killed the dinosaurs. Today, human impacts are driving a sixth mass extinction. Selectivity over space implies that most extinctions occur in a few places. This phenomenon results from the small and congruent distributions of many species, as well as those of many threatening processes. Finally, selectivity over phylogeny implies that some groups of species that are closely related (and therefore share many traits) face disproportionately high extinction risk. The greatest uncertainties about species extinctions concern causes, at all time scales. Were the “Big Five” mass extinctions caused by meteorite impacts or volcanism? Were the Pleistocene megafaunal extinctions caused by overkill or climate change? Is the current amphibian crisis caused by a spreading epidemic or a pathogen flourishing under global change? Resolving these controversies is key to extinction ecology as an applied science, because successful conservation policy and practice depend crucially on their answers. In this light, better documentation and analysis of the impacts of actions to prevent extinctions is probably the field’s single most urgent research front.

General Overviews

The field of extinction ecology lends itself well to overview and synthesis, across review papers, edited volumes, technical monographs, and popular science writing. Among review papers, Pimm, et al. 1995 is particularly influential in introducing a standard metric for reporting extinction rates across taxa and time scales. Purvis, et al. 2000 is important in setting the field on the track to become a predictive as well as a descriptive science, and Dirzo and Raven 2003 provides a strong botanical focus (within a literature that is generally animal dominated). Among edited volumes, Lawton and May 1995 is particularly pertinent in bringing together a number of important contributions to the field, while Rosenzweig 1995 is a key contribution among technical monographs. Three powerfully written books stand out among the more popular contributions to extinction ecology: Leakey and Lewin 1995, Quammen 1996, and Wilson 1992.

• Dirzo, R., and P. H. Raven. 2003. Global state of biodiversity and loss. Annual Review of Environment and Resources 28:137–167.

  DOI: 10.1146/annurev.energy.28.050302.105532

  Broad review of the magnitude, geography, and loss of modern biodiversity, with a particular focus on plants.

• Lawton, J. H., and R. M. May, eds. 1995. Extinction rates. Oxford: Oxford Univ. Press.

  Edited volume reporting on 1993 Royal Society Discussion Meeting on “Estimating Extinction Rates” and including seminal papers from many of the leaders in the field; reprinted from Philosophical Transactions of the Royal Society of London B 344.1307 (1994); the special issue is titled Estimating Extinction Rates: Sir Joseph Banks Anniversary Meeting, available online for purchase or by subscription.

• Leakey, R., and R. Lewin. 1995. The sixth extinction: Patterns of life and the future of humankind. New York: Doubleday.

  An anthropological perspective into current mass extinction, placed firmly in the geological and evolutionary context.

• Pimm, S. L., G. J. Russell, J. L. Gittleman, and T. M. Brooks. 1995. The future of biodiversity. Science 269.5222: 347–350.

  DOI: 10.1126/science.269.5222.347

  The first proposal for a standard metric, extinctions per million species-years, to standardize comparisons of extinction rates between background and current extinctions, between taxonomic groups, and between estimation methods. Heavy focus on habitat destruction as a driver of extinction.

• Purvis, A., K. E. Jones, and G. M. Mace. 2000. Extinction. BioEssays 22.12: 1123–1133.

  DOI: 10.1002/1521-1878(200012)22:12%3C1123::AID-BIES10%3E3.0.CO;2-C

  A succinct review, spanning paleontological and modern time, and with an emphasis on building predictive components to extinction ecology, to complement its strong descriptive traditions. Available online for purchase or by subscription.

• Quammen, D. 1996. The song of the dodo: Island biogeography in the age of extinctions. London: Hutchinson.

  The best popular-science account of anthropogenic extinction, providing engaging insight not only into the processes driving the current crisis, but also into the lives of those who have studied extinction from Darwin and Wallace to the present day.

• Rosenzweig, M. L. 1995. Species diversity in space and time. Cambridge, UK: Cambridge Univ. Press.

  DOI: 10.1017/CBO9780511623387

  A comprehensive overview of the ecological and evolutionary forces shaping species diversity; while many other works tackle the various components and scales of diversification, the splendid, sweeping nature of this one stands out for inclusion here as the flip side of the extinction coin.

• Wilson, E. O. 1992. The diversity of life. Questions of Science. Cambridge, MA: Belknap Press of Harvard Univ. Press.

  Beautiful and powerful treatise spanning life on earth, placing modern extinction in the context of evolutionary process and diversification.