Protecting Pollinators: How to Save the Creatures that Feed Our World
232
Protecting Pollinators: How to Save the Creatures that Feed Our World
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Overview
Product Details
| ISBN-13: | 9781610919364 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 04/18/2019 |
| Edition description: | None |
| Pages: | 232 |
| Sales rank: | 1,100,489 |
| Product dimensions: | 5.90(w) x 8.90(h) x 0.70(d) |
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CHAPTER 1
Bees and Beyond
When bees alight on flowers, something magical happens. Minute grains of pollen stick to their bodies while they gather nectar and, as the bees buzz about, moving from flower to flower, pollen grains are deposited on new flowers, triggering pollination. Though the entire process lasts mere seconds, our ecosystem depends on it.
Honeybees are credited with much of the work. Headlines like "Honey Bee Extinction Will Change Life as We Know It," "The Plight of the Honeybee," and "The World's Food Supply Could Feel the Sting of Declining Bee Populations" perpetuate the idea that bees — and honeybees in particular — are the primary pollinators of global food crops. Honeybees are important pollinators; American beekeepers crisscross the nation every year, transporting billions of honeybees to pollinate crops ranging from apples and cucumbers to pumpkins and sunflowers. Upwards of 60 percent of commercial beekeepers in the United States travel to California between February and March to place hives among the trees in 1.3 million acres of almond orchards; apiarists bring hives from as far afield as Texas and Florida. But honeybees don't deserve all of the credit for pollinating our favorite flora.
Worldwide, 200,000 different species tackle the task of pollination: vertebrates such as birds, bats, and small mammals make up a small percentage of the global pollinator population, while invertebrates such as flies, butterflies, beetles, moths, and, of course, bees make up the rest. The more widely recognized pollinators like monarch butterflies and honeybees tend to get the most attention. To wit, the honeybee is the face of the Cheerios brand and the star of the blockbuster animated film Bee Movie; monarch butterflies, with their striking orange, black, and white markings and their courageous migrations to reach overwintering grounds in milder climates, are emblazoned on the Non-GMO Project label and immortalized in coloring books and even tattoos.
While certain pollinators have been thrust into the spotlight, most of the 11,000 species of moths native to the United States fly under the radar, unrecognized despite being important pollinators. Consider the hawk moth (Sphingidae spp.). Thanks to their drab brown coloring, hawk moths are unimpressive at first glance, but looks can be deceiving. Their long, narrow wings make them fast and nimble in flight, and their tongues, which can measure up to fourteen inches long (the longest of all moth or butterfly species), make hawk moths adept at gathering nectar from flowers that would be off limits to other, less well-endowed pollinators. Because their larvae are green hornworms or tobacco worms, hawk moths are considered crop pests and often blasted with pesticides. The practice has devastated their populations, much to the relief of farmers and gardeners, but also to the detriment of rare plants like queen of the night cactus (Epiphyllum oxypetalum) and trumpet flower (Datura spp.) that depend on the long-tongued pollinator for reproduction. So, even as the unfortunate-looking hawk moth faces chemical attacks that threaten its survival, the race is on to protect prettier species like monarch butterflies and honeybees.
Issues with honeybees first came to light in 2006 when beekeepers started recording greater than normal colony losses with no apparent cause. These widespread hive abandonments were later attributed to Colony Collapse Disorder, or CCD. The colonies that succumbed to CCD, called "spring swindle disease" in historic literature, appeared healthy in the weeks leading up to the collapse. Without warning, the bees disappeared, leaving behind hives full of honey, pollen, bee bread, and capped brood. There was no evidence of dead adult bees — they simply abandoned the hive. Despite being responsible for 30-plus percent of colony losses — with beekeepers in some states attributing 90 percent of their losses to CCD — no specific causes have been identified, but several have been investigated. The first comprehensive survey of CCD losses evaluated sixty-one potential factors, from pesticides to pathogens like European foulbrood, varroa mites, and Nosema fungus, and found that no single stressor stood out as the sole cause of hive abandonment. (The study did show that CCD-affected colonies did have more pathogens and more types of pathogens than unaffected colonies.) Several other studies have since reached the same conclusions, attributing CCD to multiple stressors rather than a single cause.
Around the same time CCD was first identified, farmers began importing honeybees for the first time since 1922. Congress had passed the Honey Bee Act of 1922 in the hopes of preventing the import of hives with tracheal mites (Acarapis woodi). The mites, first reported in the United Kingdom in 1921, live in the tracheal tubes of honeybees and feed on their blood before burrowing through the tracheal tube walls and creating crusty lesions on the breathing tubes. In the earliest stages of infestation, colonies are largely unaffected. Bees traveling between hives (or between apiaries) can transfer the parasite. Tracheal mites affect flight efficiency, cause wing and abdominal deformities, and shorten lifespan. If more than 30 percent of the honeybees in a colony are infected, tracheal mites can be fatal to the entire colony. Fumigating the hive with menthol crystals, a crystalline alcohol extracted from peppermint oil, is the accepted method for controlling tracheal mites. Despite the congressional action, tracheal mites eventually did make their way to the United States. A commercial beekeeper in Texas reported the first infestation in 1984; the mites spread to seventeen states within a year.
News of CCD led Congress to change the terms of the Honey Bee Act of 1922, allowing the import of honeybees for the first time in a generation. Honeybees are native to Europe, not North America, so importing the species used to be commonplace. Farmers imported the iconic pollinators from Australia and New Zealand to help bridge the gap between winter losses and the early pollination season, particularly for the pollination of almond orchards in California.
The combined news of CCD and the appearance of tracheal mites led to some Armageddon-like predictions. With the number of US-managed honeybee colonies hovering around 2.5 million — down from 6 million in 1947 — a 2012 report from the United States Department of Agriculture (USDA) warned that "the survivorship of honeybee colonies is too low for us to be confident in our ability to meet the pollination demands of U.S. agricultural crops. ... We are one poor weather event or high winter bee loss away from a pollination disaster." Predictions were made that a honeybee crisis could lead to a tenfold increase in food prices.
Though the number of honeybee colonies has dropped by more than half over the last 70 years — declines have been blamed on a host of factors, including habitat loss, pesticide use, and climate change — nevertheless the bees have started to bounce back from CCD. During the 2017–2018 winter season, commercial beekeepers lost 26.4 percent of their hives (acceptable winter losses were 20.6 percent for the same time period), but it's not all good news for the little buzzers. These fragile creatures face serious risks to their survival. In addition to the essential role that honeybees play in agricultural production and maintaining biodiversity, scientists depend on honeybees to better understand changes in the ecosystem, including threats to general pollinator populations. In fact, most American scientific work on pollinators has focused on honeybees, though they are not native to the United States. Some research has been done on native managed species, including bumblebees and orchard bees, because, like honeybees, their populations are easy to manipulate so that their individual behaviors can be studied. The 2006 publication of the honeybee genome gave researchers another reason to focus their pollinator research on A. mellifera: sequencing the honeybee genome helped scientists understand complex biological processes that had evolved over millions of years. Christina Grozinger, director of the Center for Pollinator Research at Penn State University, explains, "There are a lot of really specific questions that you can ask with [honeybees]. You can do more-detailed experiments and more correlational research with honeybees than other bee species that are not as well understood or easy to rear. It's a model system that you can work with really well."
Honeybees are also studied extensively because of their ubiquity in agriculture. In the United States alone, more than 150 food crops require pollinators to produce fruits, seeds, and nuts; pollinators contribute up to $577 billion to annual global food production. Honeybees are the preferred pollinators because their hives can be transported between and set into agricultural fields and orchards.
While honeybees remain in the spotlight, they cannot do the job of pollination alone. Hummingbirds, bats, moths, flies, and thousands of other creatures make up the motley crew of pollinators that allow for effective and stable pollination. Diversity is more important than abundance of a single species, even a managed species like the honeybee. In fact, a 2016 meta-analysis reviewed thirty-nine studies and found that insects other than bees were also efficient pollinators, providing more than two-thirds of visits to crop flowers. Compared to honeybees, nonbee pollinators performed fewer than 50 percent of total flower visits but a higher number of flower visits and, as a result, their pollination services were on par with bees overall. The findings led researchers to suggest that shifting from a bee-only perspective was needed to get accurate assessments of crop pollinator biodiversity and the economic value of pollination. The researchers also noted that new studies should also consider the services provided by other types of "currently overlooked" but important pollinators.
"Much of the discussion and debate around pollinators and pollinator health over the past ten years has really been fueled by the honeybee; the honeybee has gotten a lot of attention," says Eric Lee-Mader, pollinator program co-director for the Xerces Society, a nonprofit focused on the conservation of invertebrates essential for biological diversity and ecosystem health. "But, out of the whole range of pollinator issues ... other pollinators seem to be faring worse."
Although we know that ants, butterflies, birds, beetles, bats, flies, moths, and wasps are important pollinators, there is a dearth of information about their populations and how each might be faring in an ever-changing landscape. Even native bees — the local cousins to the imported (nonnative) European honeybees — are not well understood.
More than 4,000 species of native bees, from carpenter bees and mason bees to bumblebees and wool-carder bees, have been identified in North America. The Center for Biological Diversity released a landmark report in 2017 that showed more than half the species with sufficient data to assess were declining, and almost one in four face the risk of extinction. Bee species without enough data to determine their current population statuses are also believed to be in peril.
A 2015 "bee map" that tracked the status of wild bee populations reported similarly discouraging findings. The map listed 139 counties across the United States where bee populations were so diminished that pollination demands couldn't be met. The affected areas, including California, the Pacific Northwest, and the Great Plains, were major agricultural production areas. The most dramatic shortfalls were found in areas with high concentrations of specialty crops like apples and berries that are especially reliant on pollinators. The researchers concluded that if wild (unmanaged) bees had adequate habitat, they could contribute to the long-term stability of crop pollination and should be integrated as either a complement or an alternative to managed bees.
Jane Ogilvie, a research fellow at the Rocky Mountain Biological Laboratory in Colorado, attributes the lack of research on native bees to their behaviors: the often-solitary species fly long distances and forage over wide swaths of the landscape, making them difficult to track in long-term or controlled experiments. Ogilvie notes, "Until we get some sort of handle on what governs the population sizes of wild bees, we're not going to know at all how to manage threats to them."
Managing threats is imperative. Both the diversity and occurrence of wild pollinators are declining, and some species have also become less abundant. A recent assessment called the Red List of Threatened Species, published by the International Union for Conservation of Nature, found that 16.5 percent of vertebrate pollinators like hummingbirds and bats are threatened with global extinction. (The number of species at risk of global extinction almost doubled — hitting 30 percent — for island inhabitants.) No global Red List exists for insect pollinators, but both regional and national assessments indicate those species are in trouble, too. Those assessments showed that populations declined 37 percent for certain species of bees and 31 percent for certain species of butterflies. In North America, the population of monarch butterflies (Danaus plexippus) declined 84% between 1996 and 2015.
Nine percent of bee and butterfly species are threatened. The rusty-patched bumblebee made history in 2017 when it became the first bumblebee species in the continental United States to be placed on the endangered species list. When pollinator populations decline — or disappear altogether — the effects are felt throughout the ecosystem.
"There is this argument, and I think it's a legitimate argument, that pollinators are sort of this critical linchpin in terrestrial ecology, [so] it should give us pause to consider that pollinators are increasingly in trouble," says Lee-Mader. "The extremely old evolutionary partnership between plants and pollinators makes them extremely important to the perpetuation of all life on earth."
Almost 90 percent of flowering plants and 75 percent of food crops depend on pollinators; the volume of pollinator-dependent food crops has increased 300 percent over the past five decades, making the global food supply more reliant on the birds and bees (and other pollinators) than ever.
Agricultural crops could be hand-pollinated. In China, where lack of habitat and excessive pesticide use have been blamed for mass bee die-offs, some farmers were forced to use paintbrushes and pots of pollen to hand-pollinate each bloom in apple and pear orchards. Critics warn that while the practice will facilitate reproduction, it is not practical: there are too few humans worldwide to manage the task. Hand-pollination is also not cost-effective: an MIT study estimated that it would cost between $5,715 and $7,135 to pollinate a one- hectare (2.5-acre) apple orchard. Based on these figures, it would cost between $409 million and $511 million to hand-pollinate the 179,146 acres of apple trees in Washington State. The result would be skyrocketing food costs and, potentially, the disappearance of certain fruit crops from store shelves.
Mini-drones have also been tested as artificial pollinators. But like the human pollen painters, so-called robot bees cannot make up for significant pollinator declines. In fact, a 2017 Newsweek article called the drones "comically inept," noting, "All of these drones are so far wildly expensive, ineffective, and would be dangerous to real bees." More importantly, technology cannot do the work pollinators have evolved to do, which includes detecting whether a plant has already been visited.
Outside of agriculture, up to 95 percent of the plant species found in natural habitats depend on animal pollination. Moreover, pollinators ensure the reproduction of fruits, nuts, and seeds that are essential food sources for herbivores like deer and wild turkeys. Just as pollinators impact the environment, the reverse is also true: a changing environment affects pollinators.
"We typically talk about the perfect storm of habitat loss, pesticide use, diseases and parasites, and those three decline factors tend to be closely linked to one another and they tend to have synergistic effects," says Lee-Mader. "There's a tangled web of different issues now that seem to be more acutely felt than we've ever seen in the history of the planet. We know, for example, that bees have fewer sources of flower nectar and flower pollen; [that] those bees having less diverse diets tend to have less robust immune systems ...; and, we think, based on a pretty ample body of research, that pesticide use can also suppress immune systems and make bees more susceptible to parasites and diseases. These things are all linked together. Climate and invasive species are also likely to have significant impacts."
It sounds hopeless, but Lee-Mader believes there is a silver lining: awareness of the issues has led to significant work being undertaken to understand the threats pollinators face and what needs to happen to address them. He notes, "There is more pollinator conservation work going on now than ever before."
(Continues…)
Excerpted from "Protecting Pollinators"
by .
Copyright © 2019 Jodi Helmer.
Excerpted by permission of ISLAND PRESS.
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