http://www.nap.edu/catalog/11761.html We ship printed books within 1 business day; personal PDFs are available immediately. Status of Pollinators in North America Committee on the Status of Pollinators in North America, National Research Council ISBN: 0-309-66381-4, 326 pages, 6 x 9, (2007) This PDF is available from the National Academies Press at: http://www.nap.edu/catalog/11761.html Visit the National Academies Press online, the authoritative source for all books from the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council: • Download hundreds of free books in PDF • Read thousands of books online for free • Explore our innovative research tools – try the “Research Dashboard” now! • Sign up to be notified when new books are published • Purchase printed books and selected PDF files Thank you for downloading this PDF. If you have comments, questions or just want more information about the books published by the National Academies Press, you may contact our customer service department toll- free at 888-624-8373, visit us online, or send an email to [email protected]. This book plus thousands more are available at http://www.nap.edu. Copyright © National Academy of Sciences. All rights reserved. Unless otherwise indicated, all materials in this PDF File are copyrighted by the National Academy of Sciences. Distribution, posting, or copying is strictly prohibited without written permission of the National Academies Press. Request reprint permission for this book. Status of Pollinators in North America http://www.nap.edu/catalog/11761.html 2 Status of Pollinators A definitive assessment of the status of pollinator populations in North America will hinge on the quality and availability of data from a variety of well-corroborated sources, and such information is not available for every taxon. Because of their economic importance, actively managed pollinators are more likely than are wild pollinators to be closely and systematically monitored. But even when standardized data are available, interpretation of patterns of population change can be difficult. Ascertaining a pattern of decline in wild pollinator species involves consideration of a broader range of sources of information, including historical accounts, natural history collections, recently published observations, and comparative analyses. For some species, population data that are sufficient to inform an assessment of pollinator status simply do not exist. POLLINATORS AND THE CONCEPT OF DECLINE Identifying population declines, particularly for insects, is problematic primarily because, for many species, there are no historical data on absolute abundance. Historical accounts (for example, Jones and Kimball, 1943) often described abundance not quantitatively but qualitatively—a species might be called “common,” “uncommon,” or “rare”—so the information is difficult to interpret or compare. There are, however, numerous reports of declines of pollinating insects that have been documented according the strict criteria of federal or state law or regulations or by nongovernmental organizations. A case in point is the Massachusetts Endangered Species Act (MESA; 321 CMR 8:00), which requires demonstration of habitat 34 Copyright © National Academy of Sciences. All rights reserved. Status of Pollinators in North America http://www.nap.edu/catalog/11761.html STATUS OF POLLINATORS 35 threat and population decline before an animal or plant can be listed as endangered, threatened, or of special concern—terms that themselves are suggestive of particular patterns of population change. However, differ- ent jurisdictions can define terms differently, and that causes difficulty for comparative studies of decline or endangerment. Some species also have inherently small populations and restricted ranges, and their relative rarity might not be the result of declining population. In determining whether pollinator populations are declining, it is impor- tant to acknowledge the distinction between a “decline” and a “shortage.” An economically driven shortage of pollinators that occurs as a result of increased demand could be entirely independent of the condition of pollina- tor populations. In this report, the term “decline” is applied to populations for which the number of individuals is decreasing over time; “shortage” means that the supply of pollinators or their services is insufficient to meet demand. The status of pollinator populations and assemblages can be as- sessed in many ways, both direct and indirect (see Appendix G for examples of methods for analyzing pollinator status). POPULATION TRENDS Insect Pollinators Although more than 750,000 insect species have been described (Grimaldi and Engel, 2005), possibly as many as 30 million more await discovery and formal description (Erwin, 1982; Stork, 1988, 1996; see also May, 1999, and Erwin, 2004). Insects comprise the most diverse assemblage of terrestrial animals, including within their ranks some of the most eco- nomically important pollinators and the dominant pollinators in a variety of natural systems. In some communities, insects pollinate as many as 93 percent of the flowering plants (Bawa, 1974, 1990; Kato, 2000). Unfortu- nately, the available taxonomic expertise does not exist to document fully the Earth’s insect biodiversity (Box 2-1); it is a virtual certainty that many insect pollinators have yet to be discovered and identified. Notwithstanding the existence of taxonomic impediments, a substantial body of information is available on pollinator population trends. The quality of this information, however, varies with taxon as, accordingly, do conclusions about the status of pollinators in these groups. Ants, Bees, and Wasps (Order Hymenoptera) The order Hymenoptera is a diverse and economically important group of approximately 125,000 described species comprising plant-feeding saw- flies, parasitic and nonparasitic wasps, ants, and bees (Zayed and Packer, Copyright © National Academy of Sciences. All rights reserved. Status of Pollinators in North America http://www.nap.edu/catalog/11761.html 36 STATUS OF POLLINATORS IN NORTH AMERICA BOX 2-1 the leadership and authority of the Convention on Biological Diversity, the Diversity and the “Taxonomic Impediment” initiative has two aims: (1) to increase the efficiency of biological systematics, and (2) to bolster the number of practicing, professional systematists. Criti- Insects account for more than half of the estimated 1,586,800 species that cal to the development of greater understanding is a supply of professional have been formally described by scientists (Grimaldi and Engel, 2005). The taxonomists, usually university-trained scientists with doctorates in their most current estimates of species undescribed or unknown to science range disciplines. from 10 million to 30 million (Grimaldi and Engel, 2005; Stork, 1988, 1996); The taxonomic impediment is far from an insoluble problem. The Con- and many of the most species-rich groups are among the least thoroughly sortium for the Barcode of Life is an international initiative to develop DNA characterized. Because of a lack of available expertise, it is often impossible barcoding as a global standard for identifying specimens. DNA barcoding uses to identify (or “determine”) specimens. a short gene sequence from a specific region of a genome as an identifying Taxonomy and its applied interface, identification, are fundamental to marker for a species (http://barcoding.si.edu). DNA barcoding promises to continuing the study and conservation of organisms. As knowledge of living provide a rapid and inexpensive means of identifying specimens by matching systems grows more comprehensive, the scientific community demands more barcode sequences with those of taxonomically validated vouchers. In the from taxonomy than simply identifying which species to avoid and which are United States, steps to ameliorate the shortage of professionals include the edible or otherwise useful. That the rate at which species are becoming extinct highly successful program of the National Science Foundation (NSF) Part- appears to exceed the rate at which new species are described (Hambler nerships for Enhancing Expertise in Taxonomy, which supports taxonomic and Speight, 1996) poses not merely an academic problem but a daunting research and training (Rodman and Cody, 2003). Assembling the Tree of challenge to understand biodiversity with economic potential before it disap- Life—another NSF effort—involves advanced molecular and optical technol- pears. The problem applies to the study of plant-pollinator interactions in North ogy, readily disseminated Web-based initiatives, and increasingly advanced America as some pollinating insects, particularly beetles and flies, are yet to analytical software. Whether the federal govenment will continue to support be discovered and described. and expand such programs is an open question. Hence, the first challenges The Global Taxonomic Initiative is attempting to reduce the bottleneck in to solving the taxonomic impediment in North America and globally are to taxonomic research resources in the face of what has been called the greatest assess available resources and identify the support and resources needed to extinction crisis in roughly 60 million years (J.A. Thomas et al., 2004). Under reduce or eliminate taxonomic impediments. 2005). The order includes within its ranks the principal managed pollina- tors of the world, bees in the genera Apis, Bombus,