Higher Global Temperatures Join Known Threats
The pleasant drone of honeybees gathering pollen on a summer day, and the rotund form of a bumblebee bobbing towards a welcoming flower are some of the delights of a flourishing garden in full bloom. Pollination is not light labor, and some busy bees can carry 30% of their body weight in golden bounty from flower to flower.
In this way, they incidentally do human beings a great service. Some 85% of flowering wild plants require the services of pollinators, and their reduction would threaten plant diversity. Also, more than a third of cultivated crops require pollination, and threats to bee and pollinator populations could impact the global food supply. There’s even evidence that the world’s insect population in general is declining—a 2016 study showed an alarming 75% decline in flying insects over a 27-year span.
A variety of efforts are underway to protect, preserve and grow bee populations, and there is evidence that bees are replenishing their numbers.
But the stressors on pollinators are still in full force and more mitigation is needed, says the NRDC (Natural Resources Defense Council), an environmental lobby group. “No, the Bees Are Not Okay,” the environmental advocacy group wrote on World Bee Day in May 2024.
Current threats to bees include parasites, destruction of habitat and food sources, and pesticides. Moreover, a study published in 2024 suggests that heatwaves and a warming planet could have devastating impacts as well.
Bountiful Honeybees
Honeybees are pollinators well-known for the delectable honey and useful wax they produce.
Archaeological evidence suggests that humans have been keeping bees since prehistoric times. The honeybee first originated in Asia about 300,000 years ago and spread to Europe and Africa, but honeybees are not native to North America—they arrived with some of the first European colonists in around 1622. Honeybees were needed not only to produce honey, but also to pollinate the European agricultural crops they brought with them.
In 2023, there were more than 2.5 million honeybee hives used for commercial pollination in the US, according to Statista.com. Due to their relative ease in transportation, honeybee hives are brought to commercial orchards and farms during flowering to pollinate crops. For instance, in the early springtime, 60% to 75% of the nation’s commercial hives are sent to California to pollinate its almond trees. From there, the US Department of Agriculture (USDA) explains, some hives will go north to pollinate orchards and berry farms, while other hives head south and east for specialized crops in those areas.
This can come at a high cost to the honeybees. The Guardian reported in 2020 that “more bees die every year in the US than all other fish and mammals combined.” Pollinating crops honeybees can be exposed to “a soup” of chemical pesticides and herbicides, including glyphosate (Roundup), which is toxic to bees, and neonicotinoids, a category of pesticide that is harmful to both the adult bees and their offspring, the British newspaper said.
[A] fatal stressor to the honeybee population is the varroa mite (Varroa destructor), a parasite that reached the United States in the late 1980s.
Another fatal stressor to the honeybee population is the varroa mite (Varroa destructor), a parasite that reached the United States in the late 1980s. These mites enter the cells of developing brood and feed on bee larvae. The emerging mites also attach themselves to worker bees. The mites weaken the bees, making them more susceptible to disease and infections. An unchecked varroa infestation can destroy an entire hive.
In 2020–2021, some US beekeepers lost over 30% of their bees per six-month season and about 45% overall after a year, due to pesticide exposure, parasites, and also diseases like colony collapse disorder.
Some apiculturists combat these losses by increasing their stock of bees every year. They can shore up hive survival by splitting colonies more frequently and replacing aging queen bees with younger queens who have been bred to maximize productivity. Thus, although high percentages of honeybees may die each year, the population of honeybees can still increase. In 2024, Axios and The Washington Post reported that a 2022 census of honeybee colonies found that more than 1 million “have popped up around the US since 2007, making them the fastest-growing type of livestock in the country.”
Rebounds in honeybee populations may be good news, but it means increased competition for resources for another population of pollinators that are experiencing declines: native bees.
Native Bees
There are more than 20,000 species of bees worldwide and 4,000 of those species are found in the United States and Canada. The only continent without native bees is Antarctica, according to The Bees in Your Back Yard: A Guide to North America’s Bees by Joseph S. Wilson and Olivia Messinger Carril.
For comparison, there are only around 1,100 different bird species in North America and only 462 known mammals.
"Among native bee species with sufficient data to assess, (1,437), more than half (749) are declining.”
Native populations of bees are not studied as well as “livestock” honeybees, who benefit from the measurable monetary gains they offer humans through honey production and pollination services. But in 2017, an unprecedented report by the Arizona-based Center for Biological Diversity said that native bees were in marked decline: “Among native bee species with sufficient data to assess, (1,437), more than half (749) are declining,” said the report. “Nearly 1 in 4 (347 native bee species) is imperiled and at increasing risk of extinction,” the report added.
To address this crisis in the US, a USDA-funded effort to monitor native bee populations was put in place in 2020. The mission of the National Native Bee Monitoring Network, which is based at University of California, Riverside, is to “unite bee researchers” and create a “robust national strategy for bee monitoring” and support.
Bees Need Biodiversity
Native bees thrive on biodiversity and are harmed by monocultures. Some native bees only collect pollen from specific plants even when other sources are available, which makes native plant conservation essential for these pollinators (Wilson & Carril, p. 22).
Native bees vary in size and color. The smallest indigenous bee is from South America (Trigona minima) and is tinier than the head of a pin, Wilson and Carril note in their book. The largest bee (Megachile pluto) was presumed extinct for more than a century before being rediscovered in 1984, but it remains rare and is about 1.5 inches long, about the size of a kumquat. Native bee coloring goes way beyond black and yellow; some bees even boast iridescent blue-green shades like those in the genus Osmia.
Bumblebees are one of nature’s most efficient pollinators.
Perhaps the most familiar native bee is the bumblebee. Bumblebee species are found throughout the Northern Hemisphere, and there are over 250 bumblebee species (Wilson & Carril, p. 242).
Bumblebees are one of nature’s most efficient pollinators. They collect pollen from many sources and can visit twice as many plants as a honeybee per minute. Bumblebees are able to “buzz pollinate,” in which the bumblebee vibrates its muscles to loosen pollen from the anthers of a flower. The result is more efficient pollination than what can be achieved by honeybees, Wilson and Carril wrote.
Bumblebees have been in decline due to lack of habitat, a warming climate, viruses, and pesticides. The UK-based Bumblebee Conservation Trust says at least two species of these jolly, useful creatures have gone extinct locally.
A Pollination Crisis
The past 50 years saw a reduction in native bee populations as well as honeybee populations in North America and Europe, according to a 2015 study. Today, the number of commercial honeybee colonies is stabilizing and even growing due to aggressive apiary management.
Still, habitat loss, pesticide exposure, and disease remain recognized drivers of bee population decline. This year, a Royal Society study of bumblebees suggests that heatwaves pose a threat to pollinators as well.
The 2024 study exposed a test group of bumblebees to high temperatures in artificial heatwaves and tracked their responses. Bees use their sense of sight to find flowers, but they also “smell” the volatile compounds of nectar and pollen released by plants. The study found that high temperatures are disruptive to this chemical communication between bees and plants—the increased heat reduced antenna sensitivity by as much as 80%.
The implications are alarming: If pollinators’ effectiveness are impaired by heat, the effects of increasing global temperatures could have devastating impacts on the global food supply and biodiversity. A 2015 study estimated that 87.5% of flowering plants (angiosperms) require pollinators. The study noted that reduced pollination could also have “knock-on” effects for other species that depend on the fruit of flowering plants for food.
Helping the Pollinators
Luckily, gardeners and nature lovers can help by planting a pollinator garden, especially those with native plant species [See The Earth & I: Homegrown National Park: Building Productive Ecosystems Where We ‘Live, Work, Play, and Pray’]. Adequate nutrition will support bees’ immune systems, so they are better equipped to survive the trials of disease and a changing climate. Organizations such as the Xerces Society can help homeowners find plants appropriate for the pollinators in their area.
But supporting pollinators doesn’t start and stop with planting flowers. Hollow plant stems and decaying wood may look untidy, but they are excellent shelters for solitary native bees raising their brood. Habitat loss is one of the most serious issues bees face, so even a small garden can create a refuge and act as a crucial way station for hungry pollinators. Plus, discovering and protecting native pollinators—their surprising diversity, beauty, and abundance—creates a whole new way to take pleasure in the natural world.
*Mal Cole is a freelance science and nature writer based in Massachusetts.
Quoted Sources: Wilson, Joseph S., and Olivia M. Carril. 2016. The Bees in Your Backyard: A Guide to North America’s Bees. Princeton, NJ: Princeton University Press.
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