Extreme Environments

by

Robert S. Boyd, Natasha Krell, Nishanta Rajakaruna

• LAST REVIEWED: 28 June 2016
• LAST MODIFIED: 28 June 2016
• DOI: 10.1093/obo/9780199830060-0152

Introduction

The study of extreme environments is an exploration of the limits of life. Organisms perform a number of basic functions (homeostasis, metabolism, growth, reproduction, etc.), and our water- and carbon-based systems are constrained within certain environmental parameters. Some organisms can push the limits of these environmental boundaries and thrive in what to most other living things are conditions inimical to life. Thus the concept of “extreme” environment is necessarily relative to conditions under which most species thrive. Organisms that live in relatively hostile environments (called extremophiles) include archaea and bacteria, but other groups of organisms also have members that can live in relatively stressful habitats. Scientists point out that there is a difference between living under extreme conditions and tolerating (perhaps by going dormant) extreme conditions, but both situations can help us understand how extreme environments affect life. The adaptations that allow organisms to live in (or survive) extreme conditions are targets of scientific study because they help us understand life’s basic processes and how life responds to environmental challenges. The lessons we learn have important applied aspects because they can help us grow food, process wastes, restore disturbed habitats, and perform many other vital tasks. In this article, we provide sections based on particularly important stress factors, but we also have included sections in which the focus is on major concepts, to show how organisms from extreme environments can inform other areas of scientific interest.

General Overviews

Each of life’s many parameters may reach extreme conditions, so that there are many resources focused on single factors or particular extreme habitats. Certainly, astrobiology considers the environmental limits of life at great extremes and thus is a rich source of information on how life responds to environmental challenges: Catling 2013 is a relatively brief overview of the broad field of astrobiology. Some single-factor overviews are included in our coverage of factors in this article (see subheadings under Major Stressors). Many overviews are based on habitats and are one way to explore particular stresses characteristic of certain habitats. Bell 2012 contains an excellent collection of chapters, each focusing on a particular extreme habitat. Additional examples of habitat-based resources include coverage of deep-sea hydrothermal vents in Van Dover 2000 and deserts in Ward 2009. Rajakaruna, et al. 2014 discusses extremophiles in the context of stressful soils derived from rocks with unusual chemistries (see also the Oxford Bibliographies in Ecology article “Geoecology,” especially the section on extremophiles). Other overviews focus on adaptations of major groups of organisms to extreme environments. As examples, Rajakaruna, et al. 2014 provides good coverage for plants (and some associated groups, such as lichens and mycorrhizae), whereas Riesch, et al. 2015 covers teleost fishes. Bakermans 2015 is a general introduction to extremophile microbes, covering all types of extremophiles, while Rampelotto 2012–2014 provides a number of review papers regarding microbes, but also some on eukaryotic organisms and their adaptations to extreme conditions. There is a strong conceptual connection between extreme environments and their effects on organisms in creating environmental stress: Schulte 2014 provides an overview of the difficulty of defining environmental stress, as well as its importance for understanding how organisms adapt to environmental extremes.

• Bakermans, Corien, ed. 2015. Microbial evolution under extreme conditions. Life in Extreme Environments 2. Berlin: De Gruyter.

  The thirteen chapters in this edited book provide an excellent introduction to microbes in extreme environments. Chapters deal with extreme temperature, pH, salinity, and radiation, as well as multiple extremes and evolutionary mechanisms.

• Bell, Elanor M., ed. 2012. Life at extremes: Environments, organisms, and strategies for survival. CABI Invasive Species 1. Wallingford, UK: CABI.

  DOI: 10.1079/9781845938147.0000

  This edited book contains twenty-eight chapters, most of which focus on a single extreme habitat. Thus, valuable introductions are provided to the stressors in each habitat and to the adaptations of organisms living in them that allow these organisms to withstand extreme environments.

• Catling, David C. 2013. Astrobiology: A very short introduction. Very Short Introductions 370. New York: Oxford Univ. Press.

  DOI: 10.1093/actrade/9780199586455.001.0001

  Part of a series of concise overviews, this book provides brief coverage of the major topics in astrobiology and is a good entry point into the contributions of astrobiology to our understanding of life in extreme environments.

• Rajakaruna, Nishanta, Robert S. Boyd, and Tanner B. Harris, eds. 2014. Plant ecology and evolution in harsh environments. Environmental Research Advances. Hauppauge, NY: Nova Science.

  This book synthesizes current scientific knowledge about a broad spectrum of harsh environments for plants (along with lichens and mycorrhizae). It includes chapters on techniques as well as particular types of stresses and thus is a good entry point into the literature for plants in extreme environments.

• Rampelotto, Pabulo H., ed. 2012–2014. Special issue: Extremophiles and extreme environments. Life.

  This “special issue,” which in fact is spread out over six issues of the journal, contains twenty-four papers that together provide a good overview of extreme environments and the organisms in them. Fifteen of the papers appear in Life 3.1 (2013), with another three both in 3.2 and 3.3 (2013) and single articles in 2.3 and 2.4 (2012) and 4.1 (2014). Most of the papers deal with microbes, but the mix of reviews along with a few research articles provides entry to many pertinent subjects.

• Riesch, Rüdiger, Michael Tobler, and Martin Plath, eds. 2015. Extremophile fishes: Ecology, evolution, and physiology of teleosts in extreme environments. New York: Springer.

  This book explores how fishes survive harsh environmental conditions, including a wide variety of unusual stressful habitats. It also explores specific adaptations as well as the role of harsh environments in speciation and the connection between extreme environments and conservation.

• Schulte, Patricia M. 2014. What is environmental stress? Insights from fish living in a variable environment. In Special issue: Stress: Challenging homeostasis. Journal of Experimental Biology 217.1: 23–34.

  DOI: 10.1242/jeb.089722

  Using Atlantic killifish as a model organism, the author reviews biological definitions of environmental stress. She also demonstrates how study of this fish has revealed the roles of adaptation and phenotypic plasticity in allowing it to thrive in a habitat that is hypervariable in temperature, salinity, and oxygenation.

• Van Dover, Cindy Lee. 2000. The ecology of deep-sea hydrothermal vents. Princeton, NJ: Princeton Univ. Press.

  A broad overview of the history and biology of these fascinating and famous extreme environments, this book is a good introduction to these habitats and the organisms in them. The author also discusses ecology and community dynamics in these unique habitats.

• Ward, David. 2009. The biology of deserts. Biology of Habitats. Oxford: Oxford Univ. Press.

  An example from a useful series of books, each focusing on a particular type of habitat, this one is an introduction to deserts and the organisms that inhabit them. It provides an entryway into the adaptations of desert organisms to the thermal and moisture stresses that characterize this habitat.