Large Herbivore Ecology, Ecosystem Dynamics and Conservation.

Large Herbivore Ecology, Ecosystem Dynamics and Conservation

Danell, K., R. Bergstrom, P. Duncan and J. Pastor, editors. 2006. Cambridge University Press Conservation Biology Series No. 11, Cambridge, UK, ISBN 13-978-0-521-53687-5 $76.95 (paper); 13-978-0-521-83005-2, $152.95 (hc); 506 pages.

In much of the north-eastern United States, white-tailed deer are so plentiful that gardeners demand herds be sterilized to save crops and politicians want deer culled to limit the spread of Lyme Disease. In Newfoundland, park managers wonder how they can maintain native biodiversity as moose, an alien invader, convert the boreal forest to little hedges and meadow. Add a massive lawnmower, such as moose or deer into an ecosystem, and one can expect dramatic changes. But, how many moose are too many? If moose were absent, what would the forest look like? Some plant species might disappear because moose are too many, while other plants disappear because moose are too few. And what of the impact on predators, songbirds, insects, soil?

These are the types of issues explored in this recent book on the ecological role of large herbivores. This 16 chapter, 28 author book is an overview of current understanding on the importance of large herbivores to ecosystems. (Note: A large herbivore typically is any mammal larger than rabbits, but, strangely, is not defined in the book). The chapters, robust and well-referenced, cover herbivore impacts and benefits in areas of nutrient cycling (by, for example, promoting productivity in grasses, or decreasing it in shrubs), species richness (by removing preferred browse species versus allowing species to persist when competitors are browsed), predation (is there stability in ecosystems?), restoration, frugivory, and climate change. As is common in disturbance ecology, the disturbance--in this case, herbivory--benefits some species while harming others. This duality is at the forefront of biodiversity issues because diversity (richness and evenness) is mainly a function of competition; as populations of large herbivores fluctuate, so does the opportunity for plant species to persist. This book contributes well to the larger issue of maintaining biodiversity.

As welcome as the book is, it is somewhat limited in scope. The role of other prominent herbivores, such as elephants, kangaroos, and domestic livestock is lacking. In semi-arid parts of Africa, India and Australia, the impact from domestic and feral goats, horses, sheep and cattle on vegetation is immense (GLASOD 1990). Considering that most of the large mammal species were extirpated in the last 10,000-40,0000 years (Martin and Wright 1967), a strong discussion of the historical bias associated with community ecology and ecosystems would have been valuable as context for the apparent role of herbivores today. As well, a non-vertebrate ecologist might wonder why the massive impact of insect her-bivory, both annually and during regular epizootics, is omitted in a discussion of community structure and evolution. And, although conservation is part of the title, there is little in the way of endangered species management; much of the 'conservation' refers to management of hunted and relatively common ungulates.

Another shortcoming is that the book emphasizes work on ungulate species of the northern hemisphere, likely a result of the book being the product of a workshop held in Sweden in 2002, and, to be fair, that most research has been done north of the Equator. There is some work from African (e.g., Serengeti, Namibia) and Peruvian sites, but most of the detailed literature refers to caribou, moose and deer. All but 2 of 28 authors reside, and mainly research herbivores, in Europe or North America.

These shortcomings do not greatly distract from the value of this book. Overall, Large Herbivore Ecology, Ecosystem Dynamics and Conservation provides a very good overview of large mammal impacts on ecological processes and species in terrestrial systems, particularly for northern temperate and boreal systems. Its principal audience is research scientists and wildlife managers and, given the emphasis on mechanistic models, it is not intended for a layman audience. The writing, layout and figures are of high quality and the editors maintain consistency across the multi-authored chapters. I would recommend this book to ecologists interested in community structure, to land managers dealing with overabundant herbivores and restoration, and to wildlife scientists working on predator-prey interaction and herbivore impacts on multiple species.

References

Global Assessment of Soil Degradation (GLASOD). 1990. United Nations Environment Programme and Food and Agricultural Organization, Switzerland.

Martin, P.S. and H.E. Wright, editors. 1967. Prehistoric Extinctions: The Search for a Cause. New Haven, CT: Yale University Press.

Reviewed by Graham Forbes, Department of Biology and the Faculty of Forestry and Environmental Management, Director of the Sir James Dunn Wildlife Research Center, University of New Brunswick, Canada.