Retrospective Book Review: Mountain Islands and Desert Seas – A Natural History of the U.S.-Mexican Borderlands

Geehlbach

by Frederick R. Gehlbach

1981, Texas A&M University Press; College Station, Texas.
Softcover.  326 pp.  Publisher's List: $24.95, Amazon: $24.95, Kindle Ebook: currently unavailable

ISBN: 978-0890965665


Review by Tom Lott
(tomlott46@gmail.com)

This review refers to my well-worn first edition of this book, which is now out of print. However, a second, softcover edition (which I have not seen) is still available from the publisher and Amazon. The ISBN and prices above refer to the softcover edition.

The title of this classic work alludes, of course, to the ecological similarity between mountains surrounded by deserts and the more traditional islands surrounded by oceans. The flora and fauna of montane areas encircled by inhospitable deserts are isolated in a manner much like the life on literal islands bordered by water. This repeated theme, characteristic of the American southwest, is thoroughly examined in this book which, in my opinion, is one of the best and most readable treatments of southwestern ecology ever written.

Its author, the late Frederick R. Gehlbach (1935-2020), longtime biology professor at Baylor University, was what I like to call a “broad spectrum” naturalist. By that I mean that he did not limit himself to the study of one particular segment of natural history. His many published works were equally familiar to herpetologists, ornithologists, mammologists, ichthyologists, and general ecologists. Consequently, I hope I will be forgiven by our predominantly herpetological-oriented readership for this review of an older book in which herpetology does not constitute the only or even the major topic. I think most serious naturalists intuitively recognize that the creatures in which we are most interested exist in ecosystems where they are affected and molded in varying degrees by every other component of that environment, whether organic or inorganic. Even the venerable Kauffeld, whose works were about as narrowly herpetological as one can get, casually took note of the habitats in which his beloved snakes had to exist.

Gehlbach’s volume is somewhat prescient in the sense that even though it was written before the current concern about global warming and climate change, it documented the ecological alterations wrought upon the southwest subsequent to significant agricultural development within the 19th century. Gehlbach uses the term “desertification” for the conversion of formerly luxuriant grasslands into desert due to range mismanagement. Unfortunately, “desertification” is a recurrent theme throughout the book.

The area covered by the book is generally within 100 miles of the US-Mexican border, extending from the mouth of the Rio Grande to the western edge of the Sonoran Desert, roughly paralleling the paths of the first (1849-1855) and second (1891-1896) US-Mexican Boundary Surveys. It is richly illustrated with lithographic artwork from volumes written to document those expeditions and supplemented with inserts of Gehlbach’s own color photographs.

The initial chapter, “Living Landscapes,” provides an overview of the geography of the borderlands in which the more detailed following chapters are set. In the subsequent chapters Gehlbach often compares his own observations with those of historical studies, such as comparing his own quantitative observations to those done much earlier to detect possible population trends. In doing so he frequently employs simple statistical tests to determine whether any deviation in his own totals is significantly different from the previous ones.

Because of this inclusion of mathematics, to which some people are constitutionally averse, I have heard a few complaints that one should have completed a course in biostatistics prior to reading this book. Having taken such a course myself, I can state that the tests Gehlbach employs are very basic ones that can be done easily with a hand-held calculator (or nowadays a phone). Without such analysis, it is difficult to determine whether two or more counts with varying results are really different or are within the limits of chance.

In other cases, however, the author relies on his qualitative impressions in comparison to earlier studies. For example, he uses his own observations over the years to agree with a previous study on the distribution of snakes along Cave Creek Canyon Road in southeastern Arizona’s Chiricahua Mountains (Pough 1966), that determined that the Mohave Rattlesnake (Crotalus scutulatus) had invaded areas formerly dominated by the Western Diamond-backed Rattlesnake (Crotalus atrox) due to the increased desertification of the preferred habitat of the latter over the past 100 years. He supplements this with a reference to a paper with similar conclusions about the invasion of the habitat of the White-tailed Deer (Odocoileus virginianus couesi) by the more desert-tolerant Mule Deer (O. hemionus) in the same range (Anthony and Smith 1977).

While there is no Literature Cited section at the end of the book to reference the numerous studies Gehlbach mentions in the text, this is more than adequately compensated for by providing complete citations in footnotes at the bottom of the page on which a work is indicated. Additionally, formulas and results of any statistical tests used are completely documented in footnotes. Plus, there is a thorough index.  

This volume contains many more such temporal faunal comparisons of a wide range of southwestern wildlife. As such, it would almost certainly enhance the knowledge base of anyone interested in the biology of that area. I have found myself consulting it frequently during the 40+ years since its initial publication. I understand that the recent softcover edition (1993) contains a new introduction by the author, which, unfortunately, I have not read. It would be interesting indeed to read Gehlbach’s thoughts on the more recent construction of the so-called border wall which restricts the movements of medium to larger animals across the border.

Literature Cited

Anthony, R. G. and N. S. Smith. 1977. “Ecological Relationships between Mule Deer and White-tailed Deer in Southeastern Arizona.” Ecol. Monogr. 47: 255-277.

Pough, H. 1966. “Ecological Relationships of Rattlesnakes in Southeastern Arizona with Notes on Other Species.” Copeia 1966: 676-683.


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