Biological Invasion: a Case Study


Global Invader: the European Green Crab. S. Behrens Yamada . 2001 . Oregon State University, Corvallis, OR. 123 pp. $15.00 (paper) . ISBN 1-881826-24-4 .

Global Invader: the European Green Crab is a concise case study of a well-known invasive species, Carcinus maenas. During the last 200 years this crab, native to the eastern shores of the Atlantic, the North Sea, and the western Baltic, was introduced and established on both coasts of North America as well as in Australia, Tasmania, and South Africa. While not as geographically impressive as the world-wide spread of black and brown rats (Rattus rattus and R. norvegicus, respectively), the global invasion of the European green crab has been arguably more carefully documented and better studied, especially along the west coast of North America.

In veterinary medicine and other disciplines, case studies are used to highlight certain aspects of a disease or process. They do not tell everything, and their specifics cannot always be extrapolated to other cases, yet they serve as important teaching tools. As written, Behrens Yamada's book on the European green crab is more than a reference text; it is a case study on biological invasion and serves as an important teaching tool for all students of ecology and invasive species, not just those interested in marine ecosystems.

The book is divided into two sections — a comprehensive review of the life history and biology of the green crab, and a historical overview of green crab invasions with emphasis on their recent introduction on the west coast of North America. The text is well referenced and serves as a valuable resource for marine biologists. The well-written prose, glossary of terms, and appendices also make it easy to read and understand for people who do not have a marine science background.

Studying the introduction and expansion of an invasive species without knowing its basic biology and life history is like reading the cover of a book and pretending you know the story. You may know the story line, but you don't know the story. Behrens Yamada recognized this and dedicated chapter one to making the reader a student of the green crab. The reader is first introduced to green crab taxonomy and life history, including its reproduction, early development and life stages, as well as postlarval development and growth. After this, Behrens Yamada compares green crab life history patterns around the world, then goes into detail about special features of green crab biology that make it a successful invader (i.e., tolerance to temperature extremes and salinity, distribution patterns, and predation). Predators and pathogens, often overlooked implications of invasion by non-native species, also are discussed. Chapter one ends with a short section on potential ecosystem impacts of green crab introduction.

By the time the reader begins chapter two, “Case histories of Green Crab Invasions,” she or he has the tools necessary to evaluate common green crab invasion patterns and the ability to understand and predict potential impacts. The sections on the ecological and economic impact of green crab invasions and invasion mitigation measures are biased strongly toward the west coast of North America. This is probably a result of the large amount of research that has been conducted on this coast since the green crab was first discovered in the San Francisco Bay in August of 1991.

By reading just the cover of this book, people could falsely think that only marine biologists would find it appealing. The truth is that this book, a well-written case study on an invasive species, has broad appeal. Invasive species, be they viruses, plants, invertebrates, or vertebrates, cause economic or environmental harm and even harm to human health. Conservation biologists need well-studied examples of invasive species for understanding and teaching the general principles of biological invasion. Behrens Yamada's book Global Invader: the European Green Crab is one of these examples.