Forest Patches in Tropical Landscapes.

Forest Patches in Tropical Landscapes. – book reviews

Julie Sloan Denslow

The effects of forest patches on the maintenance of species diversity and healthy ecological processes in tropical landscapes has attracted increasing attention as deforestation and intensification of agriculture has fragmented forests. The forest remnants discussed in these chapters are mostly small ([less than] 100 ha in many cases), distant from extensive forest, and susceptible to progressive degradation from over-exploitation or uncontrolled fires. For the most part, they are in private or community ownership and are exploited without benefit of management plans or formal protection status. They are thus unlikely to be viable conservation units by themselves. What ecological role do such patches play in the relatively homogeneous agricultural landscapes and what are the socioeconomic processes that affect landowner decisions to maintain them?

This volume is the product of a policy program sponsored by the Smithsonian Migratory Bird Center, organized initially in recognition of the importance of tropical forest remnants in Mexico and Central America for north temperate migrants on their winter feeding grounds. The collection, however, is of much broader interest than its origins would suggest.

Nineteen chapters are divided among four sections: “Changing Forests,” “Regional Landscapes,” “Human Dimensions,” and “Management.” More obviously, the chapters fall into two groups: Following an introductory chapter by Schelhas and Greenberg, the first 11 chapters address ecological processes emphasizing those occurring within forest patches. Declines in species richness of most animal groups (Robinson, Chapter 6; Guindon, Chapter 9) and gradual degradation of forest structure (Viana and Tabanez, Chapter 8) seem to doom most patches to persistence as “empty” forests. However, patches of trees also provide resources for some forest-edge and wide-ranging species of birds and mammals (Nepstad et al. Chapter 7; Greenberg, Chapter 4) and some processes, e.g. pollination, may be more resilient to isolation (Murcia, Chapter 2). Nepstad et al. (Chapter 7) emphasize that many functions of forest patches, for example, as fire breaks, depend critically on their extent and distribution. The historic relationship of patches to primary forest likely will be less important to their future than is their functional importance in agricultural landscapes.

The remaining portion of the book is devoted to the interaction of rural peoples with forests, the importance of forest products in home and local economies, and factors affecting decisions to allow fallow land to return to forest or to protect forest remnants. Woodlots may he sources of both pest predators and insect pests on crops (Power, Chapter 5), wild game and minor forest products (Alcorn, Chapter 12), and insurance against economic adversity (Schelhas, Chapter 13). However, vulnerability of both trees and game to over-exploitation (Robinson, Chapter 6) suggest that the importance of these patches in rural economies may decline.

The contributions to this volume are somewhat uneven, as symposium collections are apt to be. The degree to which most forest patches effectively contribute to the maintenance of either diversity or ecological processes is frequently asserted rather than demonstrated and I often found myself wishing for larger sample sizes, better quantification, and more extensive use of statistics. Several chapters would have benefitted from careful editing. I was disappointed that a true landscape perspective was not evident in more chapters.

Nevertheless, there are also more than a few careful, critical discussions of the causes or the consequences of forest fragmentation. Chapters by J. G. Robinson on mammals and the effects of hunting, by D. C. Nepstad and collaborators on the ecological importance of forest remnants, and by J. Schelhas on social and economic processes leading to forest fragmentation in Costa Rica are three examples.

In balance, I would recommend the book for the diversity of issues, processes, and organisms discussed and especially for the perspectives on the human dimension to the history and dynamics of patches in increasingly human-dominated landscapes in the tropics.


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