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Status of Pollinators in North America 7 Findings and Recommendations The Committee on the Status of Pollinators—a group of 15 academics, museum-based systematists, and representatives of nongovernmental organizations—convened in July 2005 and received a set of specific questions to address: Are pollinators experiencing serious decline, and if so, to what degree? What research and monitoring are needed to provide improved information? In cases where decline can be established by available data, what are its causes and how can they be addressed? What are the potential consequences of decline in agricultural and natural ecosystems? What conservation or restoration steps can be taken to slow, reverse, or prevent pollinator decline? The committee was asked to compile and analyze the published literature, determine the state of knowledge on pollinator status, identify knowledge gaps, and establish priorities for addressing these gaps. This chapter provides the committee’s recommendations as they relate to each question in the statement of task. The recommendations are aimed at improving documentation of population trends and monitoring declines, addressing the causes of decline, developing methods of stopping or reversing declines, and prioritizing research for preventing future declines. The value of determining the status of North American pollinators
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Status of Pollinators in North America became abundantly clear in short order. More than three-quarters of angiosperm plant species rely on animals for pollination. Although most major food grains are wind-pollinated grasses that do not require services of animal pollinators, most fruits and vegetables—which add diversity to the human diet and provide nutrients—are animal pollinated. Animal-pollinated crops, including several key oilseed species, also tend to be of greater economic value than are those not pollinated by animals, and they provide relatively higher income to growers. Moreover, bee pollination is required to produce the seeds of major forage and hay crops, such as alfalfa and clover, which are used to feed animals that, in turn, supply meat and dairy products. Thus, the contribution of pollinators to the quality of the human diet makes determining their status in North America an issue of prime importance. Estimating the ecological value of pollinators and pollination and predicting the consequences of their losses are considerably more challenging than estimating their economic value in agriculture. Such estimates are complicated by both the number of species involved and the relative paucity of information available for most of these species (particularly those in natural communities). As discussed in Chapter 1, it is reasonable to assume that a large proportion of flora in uncultivated terrestrial communities of North America rely upon pollinators to some degree. In a recent assessment of the susceptibility of ecosystem services to species losses (Chapter 1), animal-mediated pollination is considered a service for most ecosystems and losses of pollinator would affect trophic stability. Among the first topics examined was the question of how to differentiate between pollinator shortage and pollinator decline. Shortages and declines were recognized as distinct but not necessarily related phenomena. Shortages entail insufficient supply to meet demand according to recognized norms; declines are trends toward reduction in population size or diversity over time (Chapter 2). Using these definitions, the committee evaluated the literature and consulted numerous experts to try to determine the status of major groups of animal pollinators. MANAGED POLLINATORS Status Population status of most managed pollinators, such as bumble bees and alfalfa leafcutting bees, are not closely monitored in North America. Evidence for decline is compelling for the honey bee (Apis mellifera), which is among the few actively managed pollinator species. Current methods for documenting the status of managed colonies of A. mellifera, a species of enormous economic importance (Chapter 1), are surprisingly inadequate
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Status of Pollinators in North America (Chapters 2 and 5). Although the U.S. Department of Agriculture’s (USDA’s) National Agricultural Statistics Service (NASS) tracks managed honey bee colonies, the surveys focus on honey production rather than on pollination. The result is the double-counting of some honey-producing colonies and the omission of others that do not produce honey for commercial sale in the United States (Chapter 2). Moreover, NASS data do not consider colony strength or quality. Because data are collected in the United States, Canada, and Mexico by different methods, making direct comparisons is difficult. Recommendation: Improved information gathering for the beekeeping industry is critical, and the NASS should modify its data collection methodologies. The committee specifically recommends that NASS: Refine its assessment of honey bee abundance. The information would be more useful if all commercial honey bee colonies were counted annually and in one location only (as is currently done every 5 years for the census of agriculture). Greater accuracy also would be gained by determining whether colonies are leased for pollination, used to produce commercial honey, or both, and which use is primary. NASS should adjust its data collection to include the number of colonies lost during the previous year for any reason and the number lost over the previous winter. These data should be available by state to provide a broad picture of the overall health of the bee industry. Collect commercial honey bee pollination data from beekeepers and from crop growers. The availability of commercial honey bees as pollinators would be better understood if data were collected on the specific crops pollinated and on the leasing fees per colony by crop. Coordinate and reconcile data collection on honey bee colonies throughout North America. NASS should make its annual survey definitions compatible with its 5-year census of agriculture. The United States should work with Canada and Mexico through the North American Free Trade Agreement’s Commission for Environmental Cooperation and the Trilateral Committee for Wildlife and Ecosystem Conservation and Management to adopt common methodologies. Causes of Decline Introduced parasites and diseases have contributed to declines in managed bees. Varroa mite has had a dramatic negative impact on the abundance of honey bees in North America. Bumble bees also have suffered from a number of parasites, notably the protozoan parasites Nosema bombi and Crithidia bombi, and the tracheal mite Locustacris buchneri. Chalkbrood,
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Status of Pollinators in North America a fungal disease caused by Ascosphaera, nearly destroyed the ability to produce alfalfa leafcutting bees in the United States. For the first time since 1922, honey bees were imported in early 2005 from outside North America after a change in regulations promulgated under the terms of the Honeybee Act of 1922. Bee imports could increase the risk of introduction of pests and parasites. Recommendation: The Animal and Plant Health Inspection Service (APHIS) should ensure that its regulations prohibit introduction of new pests and parasites along with imported bees, and Congress should expand the Honey-bee Act of 1922 to include bombiculture and the fostering and breeding of other imported pollinator species. That is, Congress should extend in principle the Honeybee Act to other managed pollinator species. Other factors also could contribute to current and potential future declines in honey bee populations: antibiotic-resistant pathogens (American foulbrood); pesticide use; and the encroachment of Africanized honey bees, particularly in the southeastern United States—a major regional source of packages, queens, and migratory beekeepers for the rest of the country. Recommendation: Through research at the Agricultural Research Board (ARS) and competitive grant programs, USDA should not only continue, but also expand its efforts to: Encourage innovative approaches to protecting honey bee health by developing sustainable management programs for varroa mites, including methods for managing pesticide resistance in mite populations; identifying additional natural and synthetic pesticides and least-toxic alternatives for mite control and bee management (for example, pheromones); and developing nonchemical cultural bee management practices. Improve genetic stocks of honey bees by refining methods for identifying stocks with desirable traits and for breeding, selecting, maintaining, and improving stocks with such desirable traits as disease and pest resistance, moderated temperament, and improved honey production, taking advantage of the opportunities afforded by the recently sequenced honey bee genome; refining methods for high-quality queen production from selected stocks including controlling mating (for example
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Status of Pollinators in North America instrumental insemination, isolated mating, and drone saturation) to ensure expression of desired traits in colonies; expanding current efforts in germplasm preservation, including cryopreservation; developing methods for the maintenance of European stocks in areas of Africanization; developing a third-party certification program to ensure the quality and effectiveness of commercial queens marketed or advertised as being parasite- or pathogen-resistant (or any other specific trait); and identifying markers (expressed sequence tags and quantitative trait loci) as a support to breeding programs (Chapter 6). The achievement of these objectives will be possible only if ARS maintains current support for research and restores lost positions for scientists. A special focus will need to be placed on honey bee pollination, and reward systems for technology transfer should be developed within ARS. Although honey bees are important pollinators, there also are commercially important non-Apis species that require attention. The development of management protocols for wild species and the management of agricultural landscapes to better sustain wild pollinator populations can help supplement honey bee populations and reduce the risks associated with sole reliance on a single pollinator, particularly as pollinator demands rise and shortages become likely. Recommendation: The USDA ARS should: Create research entomology positions in its fruit and vegetable laboratories in geographically diverse regions of the United States to work on developing new non-Apis pollinators for major crops, on identifying those with potential for use as commercial pollinators, and on establishing protocols for management. These activities should augment work in the Bee Biology and Systematics Laboratory in Logan, Utah, which currently serves as a focal point for non-Apis research. Develop and implement bombiculture disease management programs to prevent pathogen spillover to wild populations. Address pathogen problems in culturing alfalfa leafcutting bees (megachileculture) to improve population sustainability and crop pollination efficacy. Conduct and encourage research on landscape and farm management as related to pollinator populations and communities, and ARS should provide guidance on pollinator-friendly management practices.
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Status of Pollinators in North America Recommendation: Private-sector funding mechanisms for honey bee health and technology transfer from federal, state, and university research facilities should be created and enhanced to meet pollination needs. Industry check-off programs, which now cover crop commodities and honey, could add honey bee pollination services to the scope of existing programs. Check off programs collect funds from an agricultural commodity group to support research and promote the commodity. This private-sector effort could complement federally funded basic research efforts and promote translational research.1 Consequences of Decline Pollinator declines will not jeopardize food supplies because grains—the world’s primary sources of dietary energy—do not depend upon animal pollinators. However, supplies of animal-pollinated foods—fruits, vegetables, and some nuts—would be affected. Among the most conspicuous demonstrable consequences of changing pollinator status in agriculture are the rising costs of pest control in apiculture (and hence rising costs for honey bee rental) that accrue from the mite management required to maintain stable honey bee populations. Honey bee rental costs also are rising because of an increase in demand from almond growers that resulted from acreage increases and seasonal instability in honey bee populations. Despite overwhelming reliance on one species, few alternative actively managed species are being used. And despite evidence of their efficacy as crop pollinators, wild species are not being exploited to the extent possible. Recommendation: USDA should establish discovery surveys for crop pollinators throughout the range of crops in North America to identify the contributions of wild species to agricultural pollination. WILD POLLINATORS Status The committee found that the strength of the evidence for population status varies from one taxon to another. In parts of their ranges, the declines in several vertebrate pollinator species, particularly bats, are evidenced by conservation program monitoring. Long-term studies by individual investigators and regional Heritage Programs also provide evidence for declines (and possible extinction in some cases) among bumble bee species and some 1 Translational research is the process of applying ideas, insights, and discoveries generated through basic scientific inquiry to industrial or agricultural uses.
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Status of Pollinators in North America butterflies as do recent additions to endangered species lists (Chapter 2). Many other pollinators (including several flies, wasps, and beetles) could be declining, even rapidly, but insufficient data are available to provide unambiguous documentation of trends. Historical data could be collected by mining museum collections. However, data mining could be difficult for species that are not well described. Insects that constitute the majority of pollinator species are less well described—taxonomically or ecologically—than are other animal pollinators. In fact, taxonomic impediments for insects are enormous with respect to documenting declines (Chapter 2). Recommendation: To address the taxonomic impediment to assessing pollinator status, the USDA’s ARS should expand basic research on the systematics of pollinators and on the development of rapid identification tools. Causes of Decline The causes of decline or factors contributing to it could be assigned definitively in only a few cases (Chapter 3). Decline in populations of some native bumble bees appears to be the result of infection with non-native protozoan parasites, including Nosema bombi and Crithidia bombi. These parasites probably came from commercial bumble bees imported from Europe for greenhouse pollination. The managed bees used in greenhouse pollination often harbor high pathogen loads, and when they escape from greenhouses, pathogen spillover into native species occurs. For some species, competition with exotic pollinators (including honey bees) can lead to population declines. Declines in many pollinator taxa also are thought to be associated with habitat loss, fragmentation, and deterioration, although in North America, data are in most cases inadequate to demonstrate causation unambiguously. One exception is the decline in bat populations that is associated with destruction of cave roosts, but there is evidence that other factors also contribute to pollinator species decline. Changes in the phenology of interactions, ranges, and distributions that lead to loss of synchrony (possibly because of global climate change) and to disruption of migratory routes (making migration an endangered phenomenon) are posited for hummingbirds, nectar-feeding bats, and some butterflies and moths. Recommendation: To prevent pathogen spillover to wild populations, APHIS should require that any commercially produced bumble bee colony shipped within the United States be certified as disease free.
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Status of Pollinators in North America Consequences of Decline The consequences of pollinator decline in nonagricultural systems are more difficult to document. Few plant species rely on a single pollinator; many have more than one. Nevertheless, there are documented examples of reduced fruit and seed set in native plants apparently in response to a paucity of pollinators. Pollen limitation of seed set is common in wild plants, but its population consequences are not clear. In the event of declining pollinator populations, some plant populations could become more vulnerable to an extinction vortex—the interacting factors that serve to progressively reduce small populations—because of the increased risks of incurring the demographic and genetic consequences of small population size. These include genetic erosion, inbreeding depression, decreased reproductive success, and greater susceptibility to catastrophes and random changes in environmental conditions. Therefore, the effects of pollinator decline on rare plant species or on those with small populations also should be given special attention. Recommendation: The U.S. Geological Survey, the Fish and Wildlife Service, and other agencies responsible for natural resource protection should establish discovery surveys for pollinators of rare, threatened, and endangered plant species. Monitoring Little is known about the status of most wild pollinators in North America because there is seldom a historical baseline with which modern data can be compared. The committee notes that systematic, thorough monitoring programs in Europe have revealed dramatic declines in pollinator abundance and diversity (Chapter 5); there are no comparable North American programs. The European experience demonstrates that monitoring is needed to document changes in populations and diversity, and that monitoring programs profit from contributions by citizen-scientists. The quality and validity of the information obtained by citizen-scientists’ monitoring should be tested and calibrated against professional science monitoring. Two sampling strategies could compensate for the absence of baseline data. First, existing historical data could be used in conjunction with contemporary survey data to guide focused assessments of the status of pollinators in specific regions of North America. Second, a long-term annual monitoring program could be initiated expressly to establish baseline data for comparison at different times in the future. In contrast to an assessment that provides a one-time snapshot, such monitoring can elucidate trends in species abundance and in the relationships between changes in community composition and their putative environmental causes. Understanding those
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Status of Pollinators in North America relationships is crucial for developing plans to mitigate environmental change and to manage for species persistence. Recommendation: The federal government should establish a network of long-term pollinator-monitoring projects that use standardized protocols and joint data-gathering interpretation in collaboration with Canada and Mexico. A rapid, one-time assessment of the current status of wild pollinators in North America to establish a baseline for long-term monitoring is a laudable initial goal. Components of this two-part assessment and monitoring program should include: assessment that targets re-surveys of areas that had been well sampled in the past and mining museum collections (specimens and labels) and the literature for historical data that correspond to areas of continuous, high-intensity sampling; monitoring that integrates the work of professional scientists and citizen-scientists in tracking pollinator status and pollination function to maximize the depth and breadth of effort. The selection of study species should correspond to the strength of evidence for decline. In view of collective evidence of population declines, bees would provide a logical initial focus. Lepidoptera constitute another group for which a compelling need for monitoring exists, given recent extinctions and the classifications of some species as endangered or threatened. Conservation and Restoration Conservation and restoration are crucial to the preservation of pollinator populations and diversity, but more must be learned about pollinator biology. Research on the basic biology and ecology of wild pollinators is inadequate. Recommendation: Because of the importance of pollination as an ecosystem service in both agricultural and natural ecosystems, the National Science Foundation and USDA should recognize pollination as a cross-cutting theme in their competitive grant programs and work together to integrate research that ranges from the genomics of honey bees and the systematics and ecology of wild pollinators to the effects of global climate change on pollinator-plant interactions. Representative areas where research is needed include:
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Status of Pollinators in North America Multidisciplinary research that promotes sustainable pollinator populations; Identification of causes and consequences (genetic erosion and pollen limitation) of pollinator decline; Ecology, restoration, conservation, and management of pollinators and pollination services, including investigation of effects of invasive plants and animals on pollination systems; and Small Business Innovation Research programs to promote technology transfer to address the health and sustainability of commercially managed pollinators. Despite sketchy data on wild pollinators, there are viable pollinator-friendly land management practices. These include, for example, providing corridors to link habitat fragments and thus to encourage pollinator movement; configuring landscape fragments to maintain pollinator populations, communities, and functions; using low- and no-till agriculture to preserve native pollinators’ nests in fields; and setting aside land for field margins to provide nesting habitat and forage for pollinators. However, these practices are not in wide use (Chapter 6), and land managers should be offered economic incentives to adopt such practices. Recommendation: Economic incentives should be expanded for pollinator conservation. State-level Natural Resources Conservation Service (NRCS) offices should provide lists of scientifically tested and approved pollinator-friendly practices to farmers participating in USDA cost-share programs (the Wildlife Habitat Incentives Program and the Environmental Quality Incentives Program), land retirement programs (the Conservation Reserve Program [CRP] and the Conservation Reserve Enhancement Program), and the production stewardship programs (Conservation Security Program [CSP]). CRP should explicitly incorporate pollinator habitat in the environmental-benefits index used to evaluate land parcel proposals. CSP should incorporate the value of pollinator habitat development into its determination of the stewardship tiers that are the basis for federal payments. USDA cost-sharing, land retirement, and production stewardship programs should be available to producers of all commodities—fruits, nuts, and vegetables—that depend on pollinators. The NRCS should target new hiring of personnel whose expertise is in biological sciences, especially ecology and natural-area management. As discussed in Chapter 5, a two-part program to assess the current
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Status of Pollinators in North America status of wild pollinators in North America and to establish a framework for long-term monitoring of pollinator populations and function over time is a laudable goal. New long-term monitoring programs should maximize results obtained per dollar spent by integrating professional scientist monitoring activity with citizen-scientist monitoring activity in assessing both pollinator status and pollination function. The professional science activities fall within the mandate of governmental agencies, including the USDA, the U.S. Geological Survey, the U.S. Fish and Wildlife Service, and the National Science Foundation’s proposed National Ecological Observatory Network. The citizen-scientist activities could be coordinated through partnerships among nongovernmental organizations (NGOs), governmental organizations, and citizen groups. Participating NGOs for a North American Pollination Monitoring Program could include the North American Pollinator Protection Campaign, the Xerces Society, Monarch Watch, and likely citizen-scientist groups such as native plant societies, gardening clubs, schools, friends of nature reserves, community farm alliances, or commodity groups. The Pollinator Watch Program in Canada is currently under development through the Environmental Monitoring and Assessment Network’s Nature Watch Program (http://www.eman-rese.ca/eman/naturewatch.html). Federal agencies could stimulate collaborative programs that encourage agency, university, and NGO scientists to work together via strategically formulated funding announcements. The participation of volunteer citizen-scientists through the NGOs could greatly increase the output of assessment programs at little additional cost. Nonfarm landowners, such as homeowners and private businesses, also could contribute to conservation of pollinators, with little investment (Box 6-3). Wildflower plantings provide resources for bees, and wood fences can provide nesting sites for twig-nesting bees. Raising public awareness and educating the next generation about the importance of pollinators and what people could do to protect them is critical. Recommendation: As part of their outreach, federal granting agencies should make an effort to enhance public understanding of the importance of pollination as an ecosystem service through support for citizen-scientist monitoring programs, teacher education, and K–12 and general public education efforts that center on pollination. Recommendation: Professional societies (Ecological Society of America, Entomological Society of America, American Association of Professional Apiculturists, Botanical Society of America) and NGOs (North American Pollinator Protection Campaign, Xerces Society for the Preservation of Endangered Invertebrates) should collaborate with landowners and the public to increase awareness of the importance of pollinators and to pub-
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Status of Pollinators in North America licize simple activities the public can do to promote and sustain pollinator abundance and diversity. Although the object of the Endangered Species Act of 1973 (ESA) is to protect endangered species and their habitats, many endangered pollinators are not recognized candidates for endangered or threatened status. Congress directed that listing of a species required a scientific determination of its continued existence as threatened or endangered, but data on many pollinators are sparse. Also, a 1981 congressional revision of the ESA specifically exempted any “species of the Class Insecta determined by the Secretary to constitute a pest whose protection under the provisions of this Act would present an overwhelming and overriding risk to man.” Some caterpillars and carpenter bees, for example, can cause or have the potential to cause damage, so it could be difficult to use ESA to achieve protection for those species. Recommendation: Congress should not consider any ESA amendment that would create additional barriers to listing pollinator species as endangered.
Representative terms from entire chapter: